Summary with Biological psychology - Kalat - 12th edition


What is biological psychology? - Chapter 1 (12)

Biological Psychology is the study of the physiological, evolutionary, and developmental mechanisms of behaviour and experience. Biological psychology tries to find a link between the build of the brains and the behaviour an organism shows. It’s not only a research field, but also a certain position. We behave because of certain brain mechanisms, which we have developed because previous animals have survived with these mechanisms and produced better than animals with other mechanisms. In order to make a connection between brains and behaviour, we need to know more about the different areas of the brain.

The writers of this book want you to remember three things:

  1. Perception happens in the brains. When something touches your hand, your hand will send a signal to the brain. You will feel it in your brain, not in your hand.

  2. Mental activity and certain types of brain activity are inseparable. This is called monism (the universe exists out of one type of material). The opposite of this is dualism (the brain exists out of one type of substance and matter is something else). Most scientists and neuroscientists support monism.

  3. You have to be careful in reporting what is an explanation and what isn’t. Research has shown that some parts of the brain are less active in depressive people. However, this doesn’t mean that less active parts of the brain cause depression. We need to know more before concluding something.

There are four categories of biological explanations of behaviour:

  1. The Physiological explanation focuses on the brain and other anatomical structures.

  2. The Ontogenetic explanation focuses on the development of structures/behaviour.

  3. The Evolutionary explanation focuses on the evolutionary history of structures/behaviour.

  4. The Functional explanation focuses on the functions of structures/behaviour, why they developed.

The mind-body problem asks the question: What is the relationship between mental activity and brain experience? There are two different approaches to this question:

  1. Dualism is the view that the mind and body function separately.

  2. Monism is the view that the mind and body are the same substance. We can identify various forms of monism: materialism (everything is physical) mentalism (the mind is a precondition for the physical world) and identity position (the mind and body are the same but described by different terms).

Do other people have consciousness? Solipsism is the belief that “I am the only one who exists”.

Animals in research

There are several reasons why animals are used as test subjects instead of humans:

  1. It is unethical to conduct certain studies using humans.

  2. Through the study of animals we gain knowledge about human evolution.

  3. Animals are interesting in themselves.

  4. Animals are similar to humans in many ways, and often it is easier to use animals.

Animal research will be a part of neuroscientific research in the future. Most of the researchers claim that a little harm should be tolerated for the sake of greater good.

Without animal research many serious diseases might remain uncured. However, there are also alternatives to animal testing.

People against animal research hold different kind of positions. Minimalists think that animal research should be firmly restricted. Justification depends on the expected value of the research, the level of harm to the animal, and the type of animal.Abolitionists think that all animals are equal to humans, so animal testing is never justifiable.

The legal standard is “the three Rs”

  1. Reduction of the number of animals.

  2. Replacement, in other words the use of substitutes (e.g. computer models) for animals whenever possible.

  3. Refinement, in other words reducing pain and discomfort as much as possible.

Universities and other institutions have committees to control animal testing.

The cells of the nervous system

The nervous system consists of two kind of specialized cells: Neurons, process and transmit information by electrical and chemical signalling and glia maintain homeostasis, form myelin, provide support and protection for neurons

An adult has approximately 100 billion neurons. Neuroscience is a relatively new branch of science. Charles Sherrington and Santiago Ramón y Cajal are considered to be the main founders of neuroscience.

Neurons are fed with glucose. For this, a large amount of oxygen is needed. Glia cells mainly need glycogen. Glucose is so important, because this is one of few things that can pass the blood-brain barrier (more on that later on).

The structure of a neuron is very much similar to the other animal cells. Most of the animal cells share the following structures:

  1. The nucleus serves as the control centre of a cell and contains the cell's chromosomal DNA.

  2. Mitochondrion perform metabolic activities and is akin to a cellular "power plant".

  3. Ribosome creates proteins.

Usually a neuron has four parts:

  1. Axon, a long branch of a neuron that conducts electrical impulses away from the soma.

  2. Soma (also called the cell body), contains the nucleus and other basic structures.

  3. Dendrites, branched projections that conduct electrical impulses received from other neurons to the soma.

  4. Presynaptic terminals, specialized junctions through which neurons signal to each other.

The myelin sheath is an insulating layer around the axon. It has intervals called the nodes of Ranvier. The myelin sheath accelerates the action potential. An afferent axon is an axon that imports information into a structure. An efferent axon is an axon that exports information from a structure. An Interneuron is a neuron that connects afferent neurons and efferent neurons in neural pathways. Neurons can vary in shape, size and function. The shape determines the connection with other neurons and thus also the contribution of a neuron to the nervous system. The function of a neuron is related to its shape.

Glial cells, sometimes called neuroglia, are non-neuronal cells with several functions:

  • Astrocytes support endothelial cells that form the blood-brain barrier, synchronise the activity of the axons, control the blood flow and remove waste material.

  • Microglia work as an immune defence in the nervous system by removing waste material and viruses.

  • Oligodendrocytes insulate the axons by building the myelin sheath.

  • Schwann cells work as oligodendrocytes.

  • Radial glia control and guide the migration of neurons.

The vertebrate brain does not replace damaged neural cells, as damaged cells in the other parts of the body are being replaced. This is why we need a blood-brain barrier. The blood-brain barrier blocks out most viruses, bacteria and harmful chemicals. However, it also blocks out most nutrients and for consequently many medications. The barrier lets different things through in different parts of the brain. The blood-brain barrier mainly exists to make the chance of brain damage as small as possible.

Some chemical can cross the blood-brain barrier:

  • Small uncharged molecules (e.g. oxygen, carbon dioxide).

  • Water (via special protein channels).

  • Molecules that dissolve in the fats of the membrane (vitamin A & D and certain types of drugs that have an influence on the brain, like antidepressants.

Some other essential chemicals are actively transported into the brain. These chemicals include glucose (energy source), amino acids, choline, some vitamins, purines, iron and some hormones.

A virus that manages to enter the nervous systems probably stays there (e.g. rabies, herpes).

The sodium-potassium pump

The membrane is selectively permeable. That means that some molecules, like the oxygen molecule, can pass through the membrane, while other molecules may never pass or rarely pass through the border of the membrane. In the membrane, there are special portals for sodium and potassium. In the resting potential, potassium can enter those portals in an average speed. The sodium portal is closed in the resting potential. With the help of a sodium-potassium pump, which is an enzyme, three sodium ions are transferred out of the membrane, while two potassium ions are transferred inside the membrane. The sodium ions will be more than ten times concentrated outside the membrane than inside the membrane and potassium ions will be more concentrated inside the membrane than outside the membrane. This will result in a difference in charge. This sodium-potassium pump is an example of active transport (energy is needed). The pump is only active because of the selective permeability of the membrane, otherwise the sodium ions that had been moved out of the membrane, would enter again. Some potassium ions that had been pumped into the membrane, will leak out again. This will increase the electrical gradient.

When a neuron is in rest, two forces are trying to get sodium into the cell: the electrical gradient and the concentration gradient. Sodium has a positive charge and the inside of the cell has a negative charge. The electrical gradient wants to pull sodium into the cell (because positive and negative charges pull each other). Sodium is more concentrated outside the cell than in the cell, which will result in the sodium ‘wanting’ to enter the cell more eagerly than leaving the cell. These two gradients will result in sodium wanting to move quickly. However, when the membrane is in rest, the sodium channels are closed and no sodium will leak to the outside (except for the sodium that is being pushed outside by the sodium-potassium pump).

Potassium also has a positive charge and the inside of the cell has a negative charge. The electrical gradient wants to pull potassium inside. But, potassium is more concentrated inside the cell than outside the cell, which will result in the concentration gradient wanting to push potassium to the outside. If the potassium channels would be open, only a small percentage of the potassium would flow to the outside. The two potassium gradients are almost equally balanced. They can’t be completely balanced because of the sodium-potassium pump.

The main functions for the sodium-potassium pump are to maintain the resting potential, transport of membrane transporter proteins and to regulate cellular volume. The resting potential’s function is to help the neuron react quickly on a stimulus.

The Action Potential

Nerve impulse is an action potential. It is an event in which the electrical membrane potential of a cell rapidly rises and falls.

Electrical gradient refers to the difference in electrical charge between the inside and outside of the cell. The inside of a cell in the phase of the resting potential is negatively charged (approximately 70mV). Resting potential is the difference in electrical charge in a resting neuron. Can be measured using microelectrode. Concentration gradient is the difference in distribution of ions across the membrane. Molecules tend to move from areas of greater concentration to areas of lesser concentration. Polarization is the difference in electrical charge between e.g. inside and outside the cell. The charge inside the neuron is slightly negative because of the charged proteins.

Voltage-gated channel is a membrane protein controlling sodium entry. At the time of depolarization those channels open. Still even during the peak of the action potential the difference between concentrations remain.

After the action potential voltage-gated potassium channels open, sodium carries a positive charge out of the axon and the membrane returns to the phase of resting potential.

Local anaesthetic drugs change the sodium channels of the membrane and prevent the flow of sodium ions (thus blocking action potential).

The All-or-none law states that the strength by which a nerve fibre responds to a stimulus is not dependent on the strength of the stimulus. If the stimulus is any strength above threshold, the nerve or muscle fibre will give a complete response or otherwise no response at all. However, the greater the frequency of action potentials, the greater the intensity of the stimulus. The refractory period is the time after action potential when the cell resists further action potentials. This can be divided into the absolute refractory period (approximately 1 ms, when the action potential is impossible in any case) and the relative refractory period (extra 2-4 ms, when the new action potential requires greater stimulus).

What are synapses and how do they work? - Chapter 2 (12)

The synapse

A synapse is a junction that permits a neuron to pass an electrical or chemical signal to another cell. A reflex is an involuntary and nearly instantaneous muscular movement in response to a stimulus. A reflex arc is a neural pathway from sensory neuron to muscle response.

The velocity of the conduction through a reflex arc is less than through an axon: this happens because of synapses, when the neurons communicate with each other.

Temporal summation is when repeated stimuli in a short time have a cumulative effect.

Spatial summation is summation over space: one weak stimulus can’t reach the threshold, but the combination of two similar stimuli located in different places can do it. This summation is essential for brain functioning. Presynaptic neuron deliver synaptic transmission. Postsynaptic neuron are in turn the receiving neuron. Excitatory postsynaptic potential (EPSP) is the temporary depolarization of a membrane (sodium gates are open). Inhibitory postsynaptic potential (IPSP) is the temporary hyperpolarization of a membrane (potassium or chloride gates are open). Inhibition is not a lack of excitation, but it actively works against it. Inhibitory neurons can work as a regulator to the timing of activity.

The nervous system has many complex patrons of connections, which produce a great amount of different reactions. You can see some of these connections in figures 2.9 to 2.11 in the book. Synapses differ in their duration of produced effects. The effect of two synapses at the same time can be more than the doubled effect of each synapse apart, or less than double. Most neurons have a spontaneous firing speed and a periodic production of action potentials, even if synaptic input isn’t present. In those cases, EPSPs increase the frequency of the action potential beyond the spontaneous firing speed and IPSPs decrease the frequency. If the spontaneous firing speed of a neuron is 10 action potentials per second, than EPSPs can increase that amount to 15 or more and IPSPs can decrease it to 5 or less.

Chemistry of a synapse

The communication between neurons is based on chemical transmission.

Chemical events at a synapse occur in the following steps:

  1. Action potential travels along the membrane of the presynaptic cell, until it reaches the synapse.

  2. The electrical depolarization of the membrane at the synapse causes channels (for calcium ions) to open.

  3. Calcium ions flow through the presynaptic membrane, rapidly increasing the calcium concentration in the interior.

  4. The high calcium concentration activates a set of calcium-sensitive proteins attached to vesicles that contain a neurotransmitter chemical.

  5. The vesicles open and dump their neurotransmitter contents into the synaptic cleft, the narrow space between the membranes of the pre- and post-synaptic cells.

  6. The neurotransmitter diffuses within the cleft. Some of it escapes, but some of it binds to chemical receptor molecules located on the membrane of the postsynaptic cell.

  7. The binding of neurotransmitter causes the receptor molecule to be activated in some way. This is the key step by which the synaptic process affects the behavior of the postsynaptic cell.

  8. Due to thermal shaking, neurotransmitter molecules eventually break loose from the receptors and drift away.

  9. The neurotransmitter is either reabsorbed by the presynaptic cell, then repackaged for future release, or else it is broken down metabolically.

Neurotransmitters

Neurotransmitters are chemicals that are released by a neuron to influence another neuron.

A neurotransmitter transmits signals from a neuron to a target cell across a synapse. More than hundred transmitters have been identified, some major categories are acetylcholines, monoamines, purines, gases, amino acids and neuropeptides. Most neurotransmitters are amino acids or a chain of these acids.

Neurotransmitter molecules are packed in vesicles (a small transport bubble that contains substances), but the presynaptic terminal also has neurotransmitters outside the vesicles. MAO (monoamine oxidase) is an enzyme in serotonin, dopamine and norepinephrine which breaks down these transmitters into inactive chemicals. Calcium in presynaptic terminal causes exocytosis (release of transmitter). After that the neurotransmitter diffuses across the synaptic cleft to the postsynaptic membrane, where it attaches to a receptor. Neurons release different kinds of neurotransmitters from different branches of their axons. However, neurons can receive and respond to many neurotransmitters at different synapses.

The effect of a neurotransmitter also depends on the receptor. There are different types of effects that can be caused. One of those effects is an ionotropic effect, which is short and direct, When a transmitter substance binds to a receiver on the membrane, the portals for a certain type of ion are opened. The channels in a synapse are transmitter-gated of ligand-gated (a ligand is a chemical substance which attaches to another chemical substance). Most exhibiting ionotropic synapses use the neurotransmitter glutamine. The most inhibiting ionotropic synapses use the neurotransmitter GABA. The other effect that can be caused is the metabotropic effect, which is slow and lengthy. They last longer than ionotropic effects, but they are also slower. They also use a huge variety and different types of neurotransmitters. Ionotropic and metabotropic synapses contribute to different types of behaviour.

After use, a neurotransmitter needs to be inactivated so that it won’t keep on exciting or blocking the receptor. This can happen in several ways:

  • Decomposition caused by an enzyme, e.g. acetylcholine is broken down by acetylcholinesterase.

  • Separation from the receptor, e.g. serotonin and catecholamines.

  • Detached transmitter can be used again via reuptake. Reuptake happens through membrane proteins called transporters.

  • Diffusion away, e.g. neuropeptides.

A negative feedback in the body is where a change in the level of one chemical leads directly to a reduction in its formation, reduction in its absorption, or increase in its excretion. Negative feedbacks are important in maintaining homeostasis in the body.

Autoreceptors take care of negative feedbacks.

Neuromodulators

Researchers sometimes call neuropeptides neuromodulators, because they have certain characteristics that differ from other transmitters. Neuropeptides are released by cell bodies, dendrites and the sides of axons. Neuropeptides are synthesised in the cell body and then transported to other parts of the cell, while most other neurotransmitters are synthesised in the presynaptic terminal. An action potential can release other neurotransmitters, but for the occurrence of neuropeptides, repeated stimulation is needed. However, when a couple of dendrites have released a neuropeptide, then the substance that has been released will prime other dendrites that are nearby to release the same neuropeptide. Neurons that have these neuropeptides, don’t release them that often, but when they do, a substantial amount is released. Neuropeptides are diffuse and they work slowly, but they have a large reach.

Neuropeptides are important for hunger, thirst, intense pain and other long-term changes in behaviour and experience.

The brains have different types of receptors. Receptors differ in their chemical characteristics, their reactions to drugs and the role they play in behaviour. Because of this, medicine that has a specialised effect on behaviour can be developed. A certain receptor can have different effects on different people, because there are many differences between the hundreds of proteins that are associated with a synapse. People differ genetically in many ways when it comes to influence on the behaviour.

A medicine or drug that looks chemically like a neurotransmitter can bind to the receptor. Many hallucinogenic drugs look chemically like serotonin. They will bind to serotonin receptors and they will give stimulation at inappropriate moments. Another example is nicotine. Nicotine is abundant on neurons that release dopamine, so nicotine increases the dopamine release there. Dopamine is associated with rewards, so the stimulation of nicotine is experienced as rewarding.

Hormones

Hormones are chemicals which are released by glands in a part of the body. These hormones are then transported through the blood stream to influence other cells. Neurotransmitters send a message to an intended receiver. Hormones send a message to every receiver on the same frequency. Neuropeptides are between these two: they are like hormones, but they are only transported throughout the brain and not to other parts of the body by blood. Figure 2.4 of the book shows a list of organs, hormones and functions. In figure 2.21 in the book you can see the most important hormone glands. One of the most important glands for hormones is the pituitary gland.

Hormones coordinate long-lasting changes in different parts of the body. Protein and peptide hormones, which exists of chains of amino acids, bind to membrane receptors at which they activate the second messenger.

What does the human Vertebrate Nervous System look like? - Chapter 3 (12)

Each part of the nervous system has specialized functions. The cerebral cortex is the largest structure and elaborately processes sensory information and provides fine control of movement. How do the areas work together? Neuroanatomy is the anatomy of the nervous system.

Structure of the Vertebrate Nervous System

Each brain area and each neuron has a specialized role, but they also depend on the cooperation with other areas. The brain and the spinal cord make up the central nervous system. The peripheral nervous system consists of nerves which run through the whole body. The somatic nervous system is the part of the PNS, that transmits messages from the sense organs to the brain and also from the brain to the muscles. The autonomic nervous system is the part of the PNS which controls the heart, intestines, and other organs. Its cells are in the brain, the spinal cord and along the spinal cord.

  1. can look at an object (like the brain) from the following perspectives: dorsal (looking frontally towards the back), ventral (looking from behind towards the chest). In brain anatomy, a structure is anterior of another, when it is closer to the forehead (closer to the front end) and posterior, when it lies further away from it (toward the rear end). A part is superior to another, when it is above and inferior when it is below another structure. There are three ways of taking a plane through the brain: horizontal (cut horizontally to see upward or downward), sagittal (cut vertically from front to back to see structures from the side), or coronal (cut horizontally from ear to ear).

Two structures are ipsiateral, when they are in the same body hemisphere and contralateral when one is left, one is right. A point is lateral of another when it is further away from the midline, more toward the side of the object investigated and medial when it is closer towards the midline. A proximal point is close to something else whereas a distal point is further away.

The bulges in the cerebral cortex are called gyri. The grooves between them are called sulci (a deep sulcus is a fissure). A ganglion is a cluster of neuron cell bodies, usually outside the CNS. A nucleus is a cluster of neuron cell bodies within the CNS. A nerve is a set of axons. A lamina is a layer of nuclei which is separated from other nuclei by axons and dendrites. Columns are vertically arranged structures which share common characteristics (e.g. function). A group of axons which connects two cells and continuously projects from the sending to the receiving one is called a track.

Grey matter consists of cell bodies and dendrites, white matter of myelinated axons. The spinal cord is the part of the CNS within the spinal column. It communicates with all sense organs and muscles (except those of the head). Each segment has a sensory (dorsal location) and a motor (ventral location) nerve. The Bell-Magendi law first stated that the dorsal nerves carry sensory information while the ventral nerves carry motor information. The cell bodies of the sensory neurons are arranged in clusters of neurons outside the spinal cord, called the dorsal root ganglia. Cell bodies of the motor neurons are inside the spinal cord. The grey matter whithin is H-shaped. If the spinal cord is cut, there is no sensual perception and motor control over the area below the cut segment.

The autonomic nervous system consists of the sympathetic (responsible for fight or flight reactions, located next to the center of the spinal cord, work in synchrony, uses neurotransmitter norepinephrine) and parasympathetic (responsible for relaxation, located along the spinal cord close to each organ, work more independently, uses acetylcholine) nervous system. As they rely on different chemicals, different drugs affect them.

Forebrain, the midbrain and the hindbrain

The hindbrain, the posterior part of the brain, consists of the medulla, pons and the cerebellum. The structures there (except the cerebellum) make up the brainstem. The medulla controls vital reflexes (e.g. breathing, heart rate) through the cranial (head) nerves. Damaging it is very dangerous. The pons is a functional bridge of the brain, where axons from each half of the brain cross to the opposite side. The raphe system sends axons to the forebrain, modifying the brain’s readiness to respond to stimuli. The cerebellum is the large hindbrain structure involved in movement, balance, attention and timing. The limbic system around the brain stem is important for motivation and emotions.

The midbrain lies in the middle of the brain. Its roof is the tectum. The sides of the tectum are the superior and inferior colliculus important for sensory processing. The substantia nigra gives rise to a dopamine-containing pathway that facilitates readiness for movement.

The forebrain consists of two hemispheres, either of which controls the contralateral side of the body. The outer portion is the cerebral cortex. The thalamus, right under it, is its major source of input. The thalamus is a pair of structures in the centre of the forebrain. Most sensory information first goes here and is then sent to the cerebral cortex. Sending back and forth focusses attention on particular stimuli. The hypothalamus conveys messages to the pituitary gland, altering its release of hormones. The basal ganglia, lateral to the thalamus, is involved in movement, learning and remembering. The nucleus basalis, part of the basal forebrain, is involved in arousal, wakefulness and attention. The hippocampus, between the thalamus and the cerebral cortex, stores memory, especially those of individual events.

The four ventricles are filled with cerebrospinal fluid, which is also found in the meninges, the membrane surrounding the brain. Pressure on it leads to a painful perception. The fluid cushions the brain against mechanical shock when the head moves.

The Cerebral Cortex

The cerebral cortex is the outer layer one sees when opening a skull. Its two hemispheres communicate through the corpus callosum and the anterior commissure. The cerebral cortex is organized similarly in mammals and occupies 13% of the brain in mammals. It contains six distinct laminae (separate layers of cell bodies parallel to the surface) differently thick in different areas. Each lamina has different functions and pathways from where they go where. Cells of the cortex are also organized in columns of cells orthogonal to the laminae. Each column reacts to a distinct body part.

The occipital lobe (fpOt) at the posterior end of the cortex is responsible for vision. The posterior pole is the primary visual cortex/striate cortex. Cortical blindness/blindsight occurs after damage to this area, not the eyes.

The parietal lobe (fPot) lies between the occipital lobe and the central sulcus (the last area of which is the postcentral gyrus including the primary somatosensory cortex responsive to touch). The postcentral gyrus consists of four bands, each of them (showing one type of stimulation) representing the body. The parietal lobe monitors all information about eye, head, and body positions and numerical information.

The temporal lobe (fpoT) processes auditory information, language most in the left lobe. It also contributes to vision, such as perception of movement and face recognition. A tumor here can make up visual and auditory hallucinations. It is also involved in emotional and motivational behaviors.

The frontal lobe (Fpot) contains the primary motor cortex and prefrontal cortex. The precentral gyrus is responsible for fine movements. The larger a species cerebral cortex, the higher the percentage of the prefrontal cortex it occupies. Neurons here have 16 times more dendrites, resulting in huge amounts of information being processed. Working memory occurs here as well as making decisions and planning movements. Damage here impairs performance on the delayed-response task.

Prefrontal lobotomy was a 20th century operation disconnecting the prefrontal cortex from the rest of the brain to “tame” people with psychological disorders. Most were performed by the founder, Freeman. Patients often became dull and apathetic, lost memory, became distractable and showed weird emotional expression.

The question of how various brain areas produce a perception of a single object is called the binding problem. Association areas rather perform advanced processing on a particular sensory system, such as vision or hearing, but few cells combine one sense with another. We can’t yet fully explain binding, but for it to occur we must perceive two stimulations as happening at the same time and place.

Research Methods

Reasons to study brain functions fall into the following categories:

  • Studying the effects of brain damage

  • Correlating anatomy of the brain with behaviour

  • Capturing the effects of a stimulated brain area

  • Capturing brain activity during the execution of behaviour

Brain damage can show which function a damaged part had. On lab rats ablations (removal or a brain area) and lesions (damages by a stereotaxic instrument-electroshock) are performed to find out about functions of brain areas. After death of the animal the brain is cut in slices and analysed as to find out which area exactly had been damaged to verify the resulting outcomes. Sham lesions are performed to compare if the effect might not rather develop because of the operation than the electric lesion. The gene-knockout approach uses biochemical methods to direct a mutation to a particular gene important for certain types of cells, transmitters, or receptors.

Stimulation of certain brain areas shows connections between behavior and brain activity. Transcranial magnet stimulation, the application of a strong magnetic field to a portion of the scalp temporarily inactivates neurons below the magnet.

Optogenetics shine laser light within the brain to activate neurons. Mild stimulations enhance brain activity, but artificial stimulation produces artificial responses. It is easier to discover which brain area is responsible for e.g. vision than to discover how it produces a meaningful pattern.

Recording brain activity during tasks shows which brain areas get activated. An EEG (electroencephalographs) records electrical activity of the brain through electrodes attached to the scalp. The electrodes measure the average activity at any moment for the population of cells under it. They can measure spontaneous or evoked potentials (responses to a stimulus). An MEG (magnetoencephalograph) works similar, but measures a magnetic field rather than electrical activity. Both procedures locate activity within a centimetre. A PET (positron-emission tomography) provides a high-resolution image of activity in a living brain by recording the emission of radioactivity from injected chemicals. Areas showing most radioactivity are the most active one (with the biggest blood flow). This is mainly replaced by fMRI (functional magnetic resonance imaging) that makes scans that record the energy released by haemoglobin molecules after removal of a magnetic field. Haemoglobin with oxygen reacts to a magnetic field differently than without oxygen, and as working areas of the brain consume oxygen, brain activity can be shown. This procedure is accurate and quick. To see which areas are active during a task, 2 images are made: without a stimulus and then with the stimulus – the differences show the area responding to the stimulus. But areas in the brain have more than one function and we have to be cautious with making inferences. To some extend it is possible to “read someone’s mind” with fMRI.

Correlating brain anatomy with behaviour can be interesting when observing unusual brains behaviour and then looking for unusual brain features. In the 1800s Franz Gall invented phrenology, which is relating skull anatomy to behavioural features. But actually there is little relationship. CT scans (computerized axial tomography) take x-rays of the brain to detect tumours or structural abnormalities. MRI (magnetic resonance imaging) applies a strong magnetic field for a short time, activating neurons and afterwards evaluates activity. This can show tiny details in brain anatomy.

In people with special skills, particular brain areas are enlarged, but not the skull above it.

Neither brain mass nor brain-to-body ratio puts human in the first place asking whether brain size is correlated with intelligence. Each species is intelligent in its own way.

When comparing brain size with intelligence, there can be an effect found, when the genders are observed separately. A given task may activate different areas in different people simply, because they approach the task in different ways. That is, a given task (even an IQ test) may be in fact a different task for different people.

Men’s brains are generally bigger and heavier (because of more white matter) than women’s, but they have the same capacities in all areas. Differences in brains between sexes are based on differences in interest and cultural influences.

How did the human Vertebrate Nervous System develop throughout evolution? - Chapter 4 (12)

Genetics and evolution of behaviour

Genes are units of heredity, which come in pairs. Chromosomes are strands of genes and they also occur in pairs (with the exception of a male mammal who has unpaired X and Y chromosomes).

DNA (deoxyribonucleic acid) is a molecule which contains genetic instructions. Its function is to work as a model for the RNA synthesis (RNA is ribonucleic acid). DNA has four fundaments: adenine, guanine, cytosine and thymine. The order of these fundaments determines the order of the corresponding fundaments on a RNA-molecule. Proteins consist of 20 amino acids and the order of these is determined by the order of the DNA and RNA fundaments. Information from DNA is converted, through RNA, into proteins, which determine the development of organs. Some important points to be made about this are:

  • DNA is a double-stranded molecule, RNA is one-stranded.

  • RNA molecule works as a model for protein synthesis.

  • Proteins either form the structure of the body or work as enzymes which are proteins that catalyse chemical reactions in the body.

  • An individual can be either homozygous or heterozygous for a certain gene, depending whether s/he has an identical (homozygous) pair of genes or unmatched pair of genes on the two chromosomes.

Genes are either dominant, recessive, or intermediate:

  • Dominant genes express what they code in every case (so, both in homozygous and heterozygous conditions).

  • Recessive genes express what they code if the two chromosomes are identical (so, only in homozygous condition).

  • Intermediate genes expression of the trait is a result of the interaction by the genes of both parents.

Chromosomes are either sex chromosomes (where the sex-linked genes are) or autosomal chromosomes (all other chromosomes). Sex chromosomes are named X and Y. women have chromosomes XX and men have chromosomes XY. Genes that are carried by either sex chromosome are said to be sex linked. Sex-limited genes are genes which are present in both sexes but turned on in only one sex. Genes can change by mutation. That is a hereditary change in the DNA molecule. Mutation means that one of the fundaments will change into one of the other three fundaments. This will be coded for a protein and this protein will have another amino acid in a certain location in the molecule. Evolution has taken ages to make the best construction for a gene and therefore new mutations are often not beneficial. Another type of mutation is doubling or elimination. During reproduction one part of a chromosome that should be present once, may be present twice or not be present at all. When this happens to a small part of a chromosome, it’s called microdeletion.

The field that is concerned with the changes in the expression of genes, without changing the DNA sequence is called epigenetics. A gene can only be active in certain cells or only in a certain time, while every gene is present in every cell of the body. Some genes are more active during puberty and others become more active during adulthood. Genes can also be turned on or off by certain experiences. To see how experiences can change the gene expression, one must first look at how the expression of genes is regulated and how environmental factors can change this.

Heredity versus environment

Classic dilemma, but the conclusion is that every behaviour is caused by both heredity and environment! The implications of heredity and environment can be studied by comparing monozygotic (having shared one zygote and therefore identical) and dizygotic twins or adopted children. Researchers have also found connections between certain genes and disorders. A distinction between the environmental and hereditary factors is difficult for several reasons. The prenatal (before birth) environment has its effects on the child. Sometimes a methyl group can attach to a gene and inactivate it. There is interaction between behaviour and the environment: a multiplier effect which states that genetics produce a small increase in some behaviour, when the environment starts to magnify that tendency. Even inherited traits can be modified by the environment. Genes do not cause certain behaviours, but they can increase their probability. Artificial selection describes intentional breeding for certain traits, or combination of traits. It is the opposite for natural selection. Genes do not change in accordance to usage of certain body parts. Genes are ‘selfish’ in that they try to multiply and evolution works for them.

Evolution

Evolution is the change over time in one or more inherited traits found in populations. Evolution looks at every change in the frequency of genes, it doesn’t matter if the genes are good or bad for the species, in the long run. We wonder how certain species have developed and how species are developing at this time. In order to answer some of these questions, we can look at fossils. There are a couple of misconceptions about evolution. Some people think that a certain body part of body function that is not being used, will be less present in future generations. Some think that the little toe is that small, because we don’t use it and they also think that the little toes of our children will be even smaller. This idea comes from Lamarck. Lamarckian evolution means that acquired traits can be inherited. However, there is no evidence for this. Another misconception is that the evolution of humans has come to a halt. This is not true. Also, some think that evolution means improvement. But, this is not always the case. Evolution enhances the fitness of the species. That means that the number of copies of someone’s/something’s genes is higher. Evolution enhances the chance that your genes are being passed on to the next generation. This is the case for good genes, but also for bad genes.

Humans have bigger and better brains than other animals (so we think). We create new solutions to problems that we haven’t come by before. How has this evolution come to play? Some think that our ancestors ate so much food, that their brains received enough fuel. Researchers tried to make guppies with bigger brains and they succeeded after a few generations. However, these guppies did have less energy for other organs and functions. This resulting in them having less offspring than they would normally have had. Evolutionary speaking, sacrificing babies for bigger brains is not good. People were able to develop those big brains without sacrificing our other functions. This was able because our diet. Our ancestors learned to cook food and to hunt together. Because of this, they had more food and they could digest their food better. Compared to chimpanzees, we have more protein that transports glucose to the brains and less protein that transports glucose to the muscles. This means that we have more energy for our brain than for our physical strength.

Evolutionary psychology examines psychological traits from a modern evolutionary perspective. It seeks to identify which human psychological traits are evolved adaptations. The emphasis of this field lies on giving an evolutionary and functional explanation. An interesting example that is studied in evolutionary psychology is altruism. Altruistic behaviour is behaviour means that you are helping another person, without benefitting from it. The concept of altruistic behaviour causes a dilemma for evolutionary psychology. Reciprocal altruism (people help those who are able to help them back) is one attempt to solve the problem. Another explanation is kin selection (we favour the reproductive success of our relatives, even at a cost to our own survival and/or reproduction).

Development of the Brain

Weight of the brain at birth is approximately 350g, at adulthood it ranges from 1200g to 1400g. Anatomy of the brain is plastic: it is changing constantly. The central nervous system start to form when the embryo is 2 weeks old. The brain and spinal cord start growing as folding lips surrounding a fluid-filled canal. The brain emerges during embryonic development from the neural tube, an early embryonic structure. The fluid-filled cavity within the neural tube becomes the central canal of the spinal cord and the four ventricles of the brain. It contains the cerebrospinal fluid (CSF).

Five processes in the development of neurons:

  1. Proliferation, production of new cells. Some cells (stem cells) keep their location and continue dividing, others differentiate as primitive neurons or glia.

  2. Migration, moving to other location. Migration is guided by immunoglobulins and chemokines. The brain has several kinds of these chemicals, which means that many things in development can go wrong but also that the absence of one chemical can be compensated by another.

  3. Differentiation, primitive neurons form their axons and dendrites.

  4. Myelination, the process in which glia produce the insulating fatty sheaths (to accelerate transmission).

  5. Synaptogenesis, formation of synapses. This process continues the whole lifetime.

New neurons do not form in the adult cerebral cortex. Still, the brain can develop some new neurons, e.g. olfactory receptor neurons. Stem cells in the brain remain immature the whole life, and they can also differentiate into new neurons in the adult hippocampus. As people get older their neurons become less changeable, and therefore learning gets more difficult. How do axons find their way to their target locations? They achieve this by following a chemical trail. Once they find their target location they arrange themselves over the area, after this the postsynaptic fine-tunes the connections by accepting certain combinations of axons.

Neural Darwinism: synapses form randomly and the process of selection keeps some and rejects others. However, in evolution mutations are random events but when it comes to neurons neurotrophins guide axonal branches in the right direction. The sympathetic nervous system forms much more neurons than it needs and muscles determine how many of them survive. Consequently, when a neuron forms a synapse onto a muscle, the muscle delivers a protein nerve growth factor (NGF). If the neuron does not receive NGF, it will end up in process called apoptosis (programmed cell death). This system explains how the number of incoming axons and receiving cells are matched.

Neurotrophins are a family of proteins that induce survival development, and the function of neurons. Also NGF and brain-derived neurotrophic factor (BDNF) are neurotrophins. While releasing neurotransmitters, neurons also release neurotrophins. Loss of neurons is a normal part of development, and actually it can be a sign of maturation. The brain is extremely sensitive to many substances in the early phases of development. Several factors can lead to impairment: toxic chemicals (e.g. alcohol), infections, malnutrition, stress etc. Fetal alcohol syndrome (FAS) is a pattern of mental and physical defects that can develop in a fetus when a woman drinks alcohol during pregnancy. Symptons are impulsiveness, hyperactivity, mental retardion, facial abnormalities, heart defects and motor problems. In FAS, many neurons receive less neurotrophins than usual and therefore undergo apoptosis. Children who are exposed to smoking before birth are at increased risk of aggressive behavior, attention-deficit disorder and impaired memory and intelligence (but smoking is not necessarely the reason, there is only correlation!). Immature neurons transplanted to new parts of the developing cortex develop characteristics of their new location. More mature neurons adopt some new properties while retaining some old ones. Our brains have an ability to remodel themselves as a response to our experinces. Axons and dendrites continue to modify their structure over the lifetime. The gain or loss of dendrite spines means a turnover of synapses, and it is probably linked to learning. Thickness of the cerebral cortex declines after approximately the 30th birthday, however both mental and especially physical activity enhance the activity of the brain, brain volume, and the thickness of the cortex. Losing a sense does not change the receptors of other sense organs, but it does increase attention to other senses. Different brain areas can change their functions to some degree, e.g. touch information can be processed by the occipital cortex in blind people. Practicing a skill (e.g. playing an instrument) reorganizes the brain to maximize performance of that skill. When compared to children playing some instrument the researchers noted that the sooner the child started playing, the more advantage they had on several tasks. Musicians have expanded representation of fingers on their cortex. However, extensive practicing can also lead to a condition where the representation of each finger overlaps with the representation of another finger. This is known as focal hand dystonia (or 'musician's cramp'').

Injuries of the Nervous system

Brain damage occurs for several reasons: radiation, tumors, infections, toxic chemicals and degenerative conditions (e.g. Alzheimer's disease).

In young people the most common reasons are closed head injury and blood clots in the veins of the brain. In older people the most common reasons are strokes:

  1. In ischemia blood flow stops because of a clot in an artery, neurons are deprived of blood. This causes loss of oxygen and glucose.

  2. In haemorrhage it is caused by a ruptured artery, neurons are flooded with blood. This causes excess of oxygen, calcium etc.

Both lead to same problems:

  1. Edema, the accumulation of fluid.

  2. Impairment of sodium-potassium pump (accumulation of sodium inside the cells).

Consequently, these combined problems lead to an excess of transmitter glutamate and overstimulation of neurons. This leads to an excess number of positive ions inside the cell. Ultimately the result is the death of neurons. Nowadays the probability of survival after ischemia is good if it is treated quickly (tPA (tissue plasminogen activator). Prospects are not as positive for hemorrhage patients. Methods of preventing brain damage after strokes:

  1. Preventing overstimulation by blocking glutamate synapses.

  2. Cooling the brain.

  3. Use of cannabinoids.

  4. Injections of omega-3 fatty acids.

After a stroke many surviving areas of the brain increase or reorganize their acitvity. They can compensate damaged areas in many ways.

Diaschisis is a sudden loss of function in an area of the brain connected to, but at a distance from a damaged area. Stimulant drugs can also be used for recovery. A whole destroyed cell can’t recover, but damaged axons can grow back. Regeneration of the axon depends whether the neurons are located in the peripheral or the central nervous system. In CNS, axons regenerate only moderately and the injury is permanent.

How does visual perception work in the human brain? - Chapter 5 (12)

Visual perception

Activation of a certain sensory nerves always conveys similar information to the brain, and therefore produces the same kind of reaction.

Information processing depends on three factors:

  • Which neurons are responding (e.g. pain).

  • The amount (amplitude) of response.

  • The timing of the response.

The law of specific nerve energies, first proposed by Johannes Müller, states that the nature of perception is defined by the pathway over which the sensory information is carried, the origin of the sensation is not important. For example, if you rub your eyes, the stimulus is perceived as visual even though it is actually the pressure on the eyes. The visual system does not duplicate the image we see, as suggested before. Instead the visual system codes it in neuronal activity. The pupil is the centre of the eye that allows light to enter the retina (inner surface of the eye). The cornea is a transparent part of the eye that covers the pupil. Together with the lens, the cornea refracts light. The route of the information from retina to the brain is indirect: first it goes to bipolar cells near the centre of the eye. The bipolar cells then pass it on to the ganglion cells directly or indirectly (via amacrine cells). The axons of the ganglion cells gather together and pass the information to the brain. The blind spot is a region of the retina where the optic nerve and blood vessels pass through to connect to the back of the eye. There are no receptors. The fovea is an area of the retina responsible for sharp central vison. It has a lot of receptors, each of these receptors are connected to a bipolar cell, and each of these bipolar cells are connected to a ganglion cell (more precisely, midget ganglion cell). Each receptor in the fovea has a straight path to the brain.

There are two kinds of visual receptors on the retina:

  • Rods are plentiful in the periphery of the retina and they work better in dim light.

  • Cones are plentiful in and around the fovea and they are responsible for colour vision. They function best in relatively bright light.

The human eye has much more rods than cones (ratio is 20:1), however cones provide the majority of the input of the brain. This is because in the fovea, all the cells, i.e. cones, have a straight path to the brain. Photopigments are chemicals in the rods and cones that deliver energy when affected by light. There are three types of cone photoreceptors. These receptors are sensitive to different portions of the visible spectrum. For humans, the visible spectrum ranges approximately from 380 to 740 nm. There are different theories related to colour vision:

  1. The Trichromatic Theory.

  2. The Opponent-Process Theory.

  3. The Retinex Theory.

Pioneers of colour vision are Thomas Young and Hermann von Helmholtz, who created the trichromatic theory of colour vision, also known as Young-Helmholtz theory, which states that we perceive colours by comparing the responses of different kind of cones. The response of a given cone varies not only with the wavelength of the light that hits it but also with its intensity, and the brain would not be able to discriminate different colours if it had input from only one type of cone. This is why interactions between at least two types of cone is necessary to produce the ability to perceive color. Different cone types are short-wavelength, medium-wavelength and long-wavelength. Short-wavelength cones are scarcer than the two other types.

The opponent process theory is based on the idea that the visual system records the differences between the responses of cones; all the colours are perceived as continuums from yellow to blue, from red to green and from white to black. Negative colour afterimage in optic illusions is an example of how this process works. It is also suggested that the bipolar cells can get fatigued after prolonged stimulation, which can cause alterations in our perception.

As the trichromatic theory and the opponent process theory could not explain colour constancy (we recognize colours even when the lighting is changing), so the retinex theory was created. This theory states that both the eye and the brain are involved in the processing, and the information from different parts of retina is combined on the cortex. People differ in the number of different types of cones they possess. That is, the people with only one or two kinds of cones have colour vision deficiency (colour blindness). Red-green colour deficiency is the most common, as 8% of men and 1% of women have it. Some women also have one extra type of cone (4 in total), but it does not change their vision drastically.

Neural basis of visual system

Overall vision consists of different aspects which are processed on different parts of cortex. All the optic nerves from both eyes meet at the optic chiasm, where approximately half of the axons lead to the other side of the brain. Lateral inhibition refers to the inhibition that neighbouring neurons in brain pathways have on each other. The practical result is sharper contrasts. The cells of the retina are on layers in the following order:

  1. Photoreceptors (rods and cones) on the bottom.

  2. Horizontal cells.

  3. Bipolar cells.

  4. Amacrine cells.

  5. Ganglion cells which lead to the lateral geniculate nucleus on the thalamus.

The horizontal cells are local cells (no axons nor action potentials), which means that its depolarization decreases with distance. It is spread in such a way that it affects many bipolar cells. Photoreceptors have naturally a certain level of activity, and light decreases their output. Because their synapses onto bipolar cells are inhibitory, light makes them decrease their inhibitory output. One photoreceptor excites one bipolar cell, and it also excites a horizontal cell which instead inhibits the very same bipolar cell. The excitatory synapse in the bipolar cell is greater than the inhibition. However, as mentioned before, the spread out horizontal cell inhibits surrounding bipolar cells which do not receive excitation; this process causes lateral inhibition. The area of the visual field from which light hits a receptor is called the receptive field of that receptor. For any cell in the visual system, the receptive field depends on which receptors are linked to that cell. There are three kinds of primate ganglion cells:

  1. The parvocellular neurons (small cell bodies and receptive fields, located in fovea) are specialized in visual details and color vision.

  2. The koniocellular neurons (small cell bodies and receptive fields, located all over the retina) have several tasks.

  3. The magnocellular neurons (large cell bodies and receptive fields, located all over the retina) are specialized in moving stimuli and large patterns.

After the information reaches the lateral geniculate nucleus it goes to primary visual cortex (also called area V1 or striate cortex) in the occipital cortex, which is important for conscious visual perception. A damage on V1 can lead to blindsight: a condition in which the person responds to visual stimuli without consciously perceiving them. Several explanations have been suggested, e.g. tiny islands of healthy tissue on V1 could produce the phenomenon, or other branches of the optic nerve convey visual information to the superior colliculus and other areas. From the primary visual cortex the information goes to secondary visual cortex (area V2) which conveys it further after processing it. The connections in the visual cortex are reciprocal.

Different pathways within the cerebral cortex respond to different stimuli. The ventral streams are visual paths in the temporal cortex and their function is to identify and recognize objects. That path is also called the ‘what-path.’ The dorsal streams are visual paths in the parietal cortex which help the motor system find and use objects. It mainly aids the visual guidance of movement and is therefore called the ‘how-path.’ The two pathways are not completely separated. Damage to the dorsal stream doesn’t seem to result in deviant vision, but people who have damage in this pathway, can’t localize where an object is at. People who have damage to the ventral path can see where objects are, but they don’t know what the objects are.

The visual cortex consists of several types of cells:

  • The simple cells are located in V1 with small, bar-shaped or edge-shaped receptive field. Fixed excitatory and inhibitory zones.

  • The complex cells are located in V1 and V2 with average, bar-shaped or edge-shaped receptive field. No fixed excitatory or inhibitory zones.

  • End-stopped cells (hypercomplex cells) are located in V1 and V2 with large, bar-shaped receptive field.

Similar cells are gathered together at the visual cortex in columns. The neurons on the visual cortex are suggested to be feature detectors, responding to a particular feature (e.g. bars). Prolonged exposure to a certain feature decreases sensitivity to that feature. In a sense, the cell is fatigued. The information processing gets more complex as the information goes further in the visual cortex. In the inferior temporal cortex it is rather complicated, that brain area takes care of the capacity of shape constancy (the ability to recognize the shape of an object even when its position or angle is changing). Visual agnosia is an inability to recognize or interpret objects in the visual field. It is caused by damage in the temporal cortex. In prosopagnosia the ability to recognize faces is impaired, while the ability to recognize other objects may be relatively intact. It is caused by damage in the fusiform gyrus. Area V4 is essential for the perception of colour constancy. It also affects visual attention. Some areas, especially MT (also known as middle-temporal cortex, or V5) and MST (medial superior temporal cortex), are specialized in motion. Motion of an object is perceived relative to its background. Saccades are quick, simultaneous movements of both eyes in the same direction. During saccades, several of the visual areas decrease their activity. In motion blindness a person cannot perceive motion in his or her visual field, despite being able to see stationary objects without issue. Some Alzheimer patients also have a mild dysfunction of motion perception. The opposite condition is also possible, a person is blind but regardless is able to see the direction in which an object is moving. All these conditions display how different areas of the brain process different kinds of visual information.

Development of the visual system

The human cortex is the most plastic during the first years of the life. Human infants start to focus on faces already during the first days of their lives. This supports the idea of an innate face recognition module. The skills in face recognition develop until adolescence. How precise the recognition is depends on the exposure to certain face characters. This is based on the process in the inferior temporal cortex: it defines the "average face", which all faces are then compared to. The development and fine-tuning of the brain requires visual experiences. It is important for the neurons of the visual cortex to receive binocular input (signals from both eyes). Axons from the eyes fight for responsiveness with each other. If the one eye is closed, the other one will outcompete its synapses, which can lead to a condition called "lazy eye". However, if both eyes remain closed for some reason, then the person will not become blind. The "lazy eye" can be treated by covering the active eye. This method will not enhance stereoscopic depth perception, but it will activate the dysfunctional eye. Other treatment is to ask a child to play a video game with three-dimensional display. Fun and beneficial for the stereoscopic depth perception at the same time! Stereoscopic depth perception is obtained by comparing the different inputs from the eyes. This happens because the brain detects retinal disparity. This will not happen if the eyes can’t work at the same time. During sensitive periods, experiences have a very strong influence. Different aspects of vision have different sensitive periods. After the sensitive period the visual cortex will not change much. E.g. those who are not exposed to moving stimuli early in life will become motion blind. Inhibition by GABA starts the sensitive period, and researchers are hopeful they could relaunch the sensitive period by blocking GABA receptors.

Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. Approximately 70% of infants have this condition, though its prevalence diminishes significantly with age. A cataract is a clouding of the lens in the eye. The sooner the visual impairments are fixed, the better the recovery, though some subtle visual deficits remain.

How do the other human sensory systems work? - Chapter 6 (12)

Audition

Physically sound waves are compressions of air, water etc. The amplitude of a wave refers to its intensity. Loudness differs from amplitude. The frequency refers to the number of compressions per second (in hertz, Hz). The human ear can detect sounds within the range 15-20,000 Hz. The higher the frequency, the higher the pitch.

The ear

Structures of the ear fall into three categories:

  1. The outer ear, which consists of the pinna (helps to locate the source of a sound).

  2. The middle ear, which contains the tympanic membrane (the eardrum) which vibrates the sound to three bones (hammer, anvil and stirrup).

  3. The inner ear, which contains the oval window and the cochlea. In this, there are three channels with liquid: the scala vestibule, the scala media and the scala tympani. Because of the stirrup, the oval window at the entrance of the scala vestibule vibrates, which sets the liquid in the cochlea in motion. Between the basilar membrane of the cochlea on one side and the tectorial membrane on the other side, hair cells are located. These are audio receptors. The hair cells move because of the vibrations in the liquid of the cochlea. This will result in the opening of the ion channels in the membrane.

There are different theories about how we actually differentiate between sounds:

  1. Place theory is a theory which states that our perception of sound depends on where each component frequency produces vibrations along the basilar membrane.

  2. Frequency theory states that the basilar membrane synchronized with a sound so that the nerve axon produces action potentials of the same frequency.

  3. Current perspective contains some parts of both of these theories: Volley principle attempts to account for the maximum theoretical limit for the neuronal firing of action potentials and the small time scales over which sound discrimination must occur. Auditory cells time their responses very precisely.

Most of our hearing occurs under 4000 Hz. People differ in sensitivity to pitch. Amusia refers to an impaired ability to detect frequency changes. Amusia has a genetic base and it is caused by weak connections between the auditory cortex and other brain areas. Absolute pitch refers to ability to recognize a note. Most people are either very accurate or not accurate at all; extensive musical training is important. Speakers of tonal languages have more often absolute pitch.

Auditory cortex

Auditory information is processed on the primary auditory cortex A1 (a part of the superior temporal cortex). Also audition has a "what" pathway and a "how" pathway, the first one being sensitive to patterns of sounds and the second one to sound location. Therefore it is possible to be motion deaf. The development of the auditory system requires experience. A damage on the primary auditory cortex does not lead to deafness. Instead, the auditory cortex offers a “map" of the sound (tonotopic map), and therefore damage can lead to impairments in processing auditory information. The cells in the auditory cortex are more responsive to one kind of preferred sound. There are also other auditory areas in the brain, but they process sounds from different perspective.

Hearing impairments

Two types of hearing impairments have been distinguished:

  • Conductive deafness (also middle-ear deafness) is caused by e.g. tumours or diseases

  • Nerve deafness is caused by a damage in the cochlea, the hair cells or the auditory nerve.

Some prenatal conditions can result in nerve deafness, e.g. lack of oxygen during birth, exposure to certain drugs, and exposure to diseases such as syphilis or meningitis. Nerve deafness can also be inherited. With two ears we can localize the source of a sound. One cue is the difference in intensity between the ears. The second cue is that sound waves arrive at the ears in different times. The third cue is the phase difference which is used with low frequencies, loudness differences are used with high frequencies. Many old people keep having hearing impairments, even when they have a hearing-aid. The hearing-aid makes the sound loud enough, but people have trouble with understanding speech, especially in noisy places. It appears that the brain area for speech comprehension has become less active. This can be because of a natural development, or because someone has ‘neglected’ his/her auditory input for a long time. When you just keep stalling the use of an hearing-aid, your language cortex will not receive its usual input and it will become less receptive. Also, older people have less neurotransmitters for inhibition in the auditory part of the brain and because of this, they have trouble with inhibiting unimportant sounds in a certain location. They will have less attention for relevant conversations.

The Mechanical Senses

The mechanical senses detect mechanical stimuli, e.g. touch, pain and balance. Also audition is a mechanical sense because the hair cells are a form of touch receptors. The vestibular system is a sensory system that provides the leading contribution about movement and sense of balance. The vestibular organ function is to detect the direction of tilt and the acceleration of the head. The vestibular organ consists of the saccule, utricle and three semicircular canals. The hair cells are located in those semicircular canals and next to the hair cells lie particles called otoliths. Otoliths move different hair cells when the head tilts in some direction. The somatosensory system refers to the movements and sensations of the body. It includes different senses including pressure, cold, warmth, pain, tickle, itch, discriminative touch and the position and movement of joints. Most of the receptors respond to different kinds of stimuli, e.g. to pain, warmth and cold.

A touch receptor can be a bare neuron ending, an elaborated neuron ending or a bare ending surrounded by other cells that affects its functioning. Pacinian corpuscles are one of the four major types of mechanoreceptor. They are nerve endings in the skin, responsible for sensitivity to vibration and pressure. Besides the changes in temperature, also certain chemicals can induce the feeling of coolness or warmth. Capsaicin is a chemical which stimulates the heat receptors. Menthol and mint cause a feeling of coolness. Information from touch receptors is gathered through the cranial nerves (head) and through the spinal nerves (other parts of the body). Every spinal nerve has a sensory component and a motor component. Each spinal nerve also innervates (supplies with nerves) a certain area, a dermatome. These dermatomes overlap with each other.

Different kinds of sensory information have different pathways into the brain. Therefore the aspects of body sensations stay apart on the way to the cortex. For the conscious experiences of touch, the primary somatosensory cortex is the key player. The experience is not necessarily the same as the stimulus, e.g. you can feel two touches nearby each other as one somewhere in between those touches. The perception of the body can become distorted as a result of damage to the somatosensory cortex.

Pain

Pain receptors are bare nerve endings, and they can respond to pressure, acids and heat. The axons of the pain receptors have only a little myelin and therefore their conductance is not very quick; however, the brain processes pain information quickly. The axons conducting pain information release two transmitters:

  • Glutamate which is released after mild pain.

  • Substance P which is released after severe injury together with glutamate.

Pain information has two pathways to the brain: To the somatosensory cortex, where the sensory information is led and to the cingulate cortex, which is responsible for the emotional feeling of pain (e.g. "sympathetic pain"). The function of the pain is to alert from the danger threatening the tissue. Therefore it is dangerous not to feel pain. Continuing pain is decreased by opioid mechanisms, which work by blocking the release of substance P. The body also has its own opiate-type chemicals, called endorphins. Endorphins are released as a response to pain, but also during sexual intercourse or listening to music. Other things that can decrease pain are placebos and cannabinoids. A placebo is a fake medicine, which can cause actual effects, e.g. they can relieve pain. This happens, however, through mental processes: a placebo decreases the functioning of the cingulate cortex but not the somatosensory cortex. In a chemical level the function of placebos is partly based on the release of opiates. A nocebo is an antiplacebo, which can increase pain by causing anxiety. Cannabinoids and capsaicin can be used to relieve pain. Also electrical stimulation of the spinal cord or the thalamus can be effective, though most of the patients do not report long-lasting pain reduction. As the body has mechanisms to reduce pain, it has also mechanisms to induce it. Damaged skin releases chemicals (e.g. histamin) which help recovery but at the same time stimulate pain receptors nearby. Anti-inflammatory drugs (e.g. ibuprofen) works by reducing the release of those chemicals.

Synaptic receptors can "strengthen", so that similar input in the future causes a stronger response. This kind of mechanism is essential for learning, but is a burden when it comes to painful stimuli. In the past, itch was considered as a form of pain, nowadays they are separated from each other. The relationship between pain and itch is inhibitory (e.g. opiates decrease pain but increase itch). One spinal pathway is responsible for itch, and the response is rather slow. Itch causes a release of a chemical called gastring-releasing peptide.

Taste and Olfaction

A sensory system can use two types of coding: labelled-line principle and across-fibre pattern principle. In the labelled-line principle, receptors respond to certain stimuli and the meaning depends on which neurons are active. In the across-fibre pattern principle, receptors respond to many stimuli and the meaning depends on the relationship of neurons.

Taste

Taste buds contain taste receptors on the tongue (on the papillae), and actually they are modified skin cells. Taste receptors are also replaced rather often, like skin cells. Flavour refers to a combination of taste and smell. Both taste and smell axons are connected to the endopiriform cortex. Traditionally four primary tastes have been separated: sweet, salty, sour and bitter. Also a fifth has been suggested: glutamate (umami). Adaptation refers to the fatigue of the receptor after exposure to a certain taste. Cross-adaptation means weaker response to one taste after exposure to another. Different substances excite different receptors and strike different sequences of action potentials. A receptor which responds to salty taste detects sodium. Sour receptor detect acids. Sweetness, bitterness and umami are similar to each other chemically. Bitter substances are usually somewhat toxic. Taste information from the tongue goes along the seventh, ninth and tenth cranial nerves. These nerves project to the nucleus of the tractus solitarius. From there the message shatters to several brain areas. Individual differences in tasting are huge. Some people are non-tasters, as some are the other extreme: supertasters. Supertasters are prone to avoiding strong-tasting foods. Taste sensitivity is linked to the number of fusiform papillae on the tongue.

Smell

Olfaction refers to the sense of smell. Membranes inside the nose respond to chemicals. Olfaction is important for most of the mammals, though it is not that important to humans anymore. However, it can be improved a lot with practice. Olfaction’s function is to detect eatable foods. It plays a part also in social settings: when people are asked who they would prefer as a potential partner they prefer people who smell similar to themselves, but not too similar. Evolutionary speaking, dating someone who smells really similar to you, isn’t good. That’s because this person might be your relative and it’s not good to have offspring with your relative. It is estimated that humans have several hundred olfactory receptor proteins. The amount is so huge because olfaction does not work as a single continuum. Olfaction adapts quickly. It is faster than researchers once believed. The message from an olfactory receptor goes to the olfactory bulb, and from there to the olfactory area on the cerebral cortex. Experience can teach us to differentiate better between similar smells. Olfactory receptors are rather vulnerable to damage. Women are more sensitive to smells than men. We don't yet know much about genetic variations when it comes to olfactory, but there are significant differences.

Receptors in the vomeronasal organ (VNO) are specialized to detect pheromones. Pheromones are chemicals which have an especially sexual impact on other humans/animals. VNO receptors do not adapt as olfactory receptors adapt. However in humans VNO is small and has no receptors, but we have some other receptor resembling those in VNO. Probably pheromones affect our behaviour unconsciously. Women who spend a lot of time together synchronize their menstrual cycles. In sum, body secretions work as pheromones and affect us in subtle ways.

Synaesthesia

Synaesthesia is a condition in which stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway. For example a smell can be perceived as a colour. One might say that spaghetti tastes red. One hypothesis for the occurrence of synaesthesia is that some axons of a cortical area branch out in another cortical area. Another hypothesis is that people with synaesthesia have more grey matter in certain brain areas. What causes synaesthesia? Synaesthesia often occurs in families, thus it appears that synaesthesia has a genetic component. Of course, nobody is born with a certain type of letter-colour or number-colour synaesthesia (after all, you’re not born with alphabetical knowledge). One research has found that early experiences can have an influence on the development of synaesthesia. One research has shown that there is a relation between a small group of children who used to play with refrigerator magnets and the development of letter-colour synaesthesia. The children learned the letters, but they also remembered the colours of every letter (so the A was red, the B was blue and the C was green). Because of that, they might have developed synaesthesia and are experiencing letters in colour. However, this is only a small part of the explanation of the development of synaesthesia (many children who play with refrigerator magnets, don’t develop synaesthesia).

How can the human brain control body movement? - Chapter 7 (12)

The control of movement: Muscle and muscle movement

Muscle contractions produce movements. Three different kinds of muscles are distinguished:

  1. Smooth muscles: inner organs. Cells are long and thin.

  2. Skeletal (striated) muscles: movements of the body. Cells are striped and long.

  3. Cardiac muscles: heart contractions. Cells are connected to each other, and therefore they all contract at once.

Fibres form muscles. Each muscle receives information from only one axon, but one axon can innervate several muscles. A synapse between a motor neuron axon and a muscle fibre is called a neuromuscular junction. Acetylcholine is a neurotransmitter that is released in the junction and it makes the muscle contract. Most muscles work in pairs, as flexor and extensor muscles. These opposing sets of muscles are called antagonistic muscles. Myasthenia gravis is a disease characterized by fatigue of skeletal muscles. The cause is the impairment in acetylcholine receptors. We have two kinds of muscle types:

  1. Fast-twitch fibres, which are anaerobic, get easily tired. On the other hand the contraction is fast.

  2. Slow-twitch fibres, which are aerobic, do not fatigue easily. The contraction is strenuous.

Individuals differ in the number of fast-twitch fibres and slow-twitch fibres. Proprioception is the sense of the relative position of neighbouring parts of the body. A proprioceptor is a receptor of this sense, they detect the tension and stretch of a muscle. When the muscles is stretched, a reflex will contract it as well - this is called a stretch reflex. A muscle spindle is sort of a proprioceptor. Another type is a golgi tendon organ, which detects the variations in muscle tension. It works as a brake; if the tension is too much they inhibit further contraction. A reflex is an automatic response to a stimulus, e.g. pupil changes when light hits it.

Infants have some reflexes adults do not have:

  1. Grasp reflex, an infant grasps an object which is placed in his/her hand.

  2. Babinski reflex, extension of the big toe when touching the sole of the foot.

  3. Rooting reflex, an infant turns his/her head when the cheek is being touched.

Most of the movement consists of voluntary and involuntary movements. Movements vary in how they respond to feedback. Ballistic movements do not correct themselves. Some actions are quick sequences, such as speaking, writing etc. A central pattern generator is a neural mechanism generating rhythmic patterns Built-in movements occurring in a fixed sequence are called motor programs (e.g. yawning).

Neural Basis of Movement

The primary motor cortex is important in eliciting movements, especially intended movements. The motor cortex innervates muscles via the brainstem and spinal cord. There are several areas important for moving near the primary motor cortex:

  • The posterior parietal cortex detects the body’s position in relation to the surrounding world.

  • The primary somatosensory cortex processes sensory information, e.g. touch.

  • The prefrontal cortex detects lights, sounds and other signals affecting to movement. Furthermore, it considers the probable outcomes of movements.

  • The premotor cortex participates in preparing a movement.

  • The supplementary motor cortex plans and organizes sequences of movements.

Mirror neurons

Mirror neurons are neurons which activate while preparing for the action and while watching someone else performing. This is interesting, because mirror neurons can be important for understanding other people, identifying with them and learning from them. Still it is not clear whether mirror neurons cause imitations or if they are developed by the imitation. At least some of them develop their mirror qualities. It is suggested that dysfunctional mirror neurons are part of autistic disorder.

Conscious decisions about movement

Before an activity, the motor cortex produces a readiness potential - the brain activity for the movement starts before a conscious decision. The previous fact does not mean we do involuntary movements, but that our voluntary movement is unconscious in the beginning. The corticospinal tracts are paths from the cerebral cortex to the spinal cord. We have two of those tracts: the lateral corticospinal tract and the medial corticospinal tract. The lateral corticospinal tract controls movements in peripheral areas (hands and feet). Axons of this tract connect directly to their target neurons. The medial corticospinal tract control movements of the neck, shoulders and trunk, and therefore it is related to walking, sitting, turning etc. Both paths cross in the medulla.

The cerebellum

The cerebellum is an important area for balance and coordination. Damage to that area produces clumsiness, speaking problems, and inaccurate eye movements. The individual has problems with activities requiring timing and aiming. However, the cerebellum also responds to sensory stimulation without movements. The cerebellum also affects attention: people with cerebellar damage require more time when they have to shift their attention. Someone who has damage to his cerebellum, will have trouble to program distances with eye movements. The symptoms of damage to the cerebellum look like the symptoms of being drunk/alcohol poisoning: clumsiness, strange eye movements and irregular speech.

The cerebellum receives information from the spinal cord and the sensory systems. The information from the cerebellum goes to the cerebellar cortex. The neurons on the cerebellar cortex have a geometrical pattern. The Purkinje cells and the parallel fibres are located on the cerebellar cortex. Action potentials excite one Purkinje cell after the other. These Purkinje cells send an inhibiting message to the cells in the nuclei of the cerebellum and the vestibular nuclei in the brain stem. These will in turn send the information to the mid brain and the thalamus. The output of a Purkinje cell determines the timing of a movement.

Basal ganglia

The basal ganglia refers to a group of subcortical structures in the forebrain, such as the caudate nucleus, the putamen and the globus pallidus. Not everyone agrees which structures belong to the basal ganglia, but all scientists do agree that the three previous mentioned structures belong to the basal ganglia. You can look at page 245 of the book to see the input and output of the basal ganglia. The caudate nucleus and the putamen together are called striatum or dorsal striatum. The caudate nucleus and putamen controls which movements to stop inhibiting. The caudate nucleus and the putamen send their information to the globus pallidus. The basal ganglia select a movement by stopping the inhibition of this movement. There is a direct route and an indirect route. Both are active for a movement and none is active when the animal is resting. The direct route enhances the selected movement and the indirect route inhibits inappropriate, competing movements. The indirect route is essential for learned performances. The basal ganglia is important for initiating an action and learning new habits. The basal ganglia seems essential for initiating a behaviour, but not when the reaction directly follows a stimulus. Movements that have been initiated by oneself, are usually slower than movements that have been initiated by a stimulus. When you want to switch lanes, you will probably move/react slower than when you see an animal on the road. Research has shown that cells in the primary motor cortex become active before the cells in the basal ganglia become active and this means that the basal ganglia are not responsible for the selection of movement. The role of the basal ganglia is to regulate the velocity of the movement. Many cells in the basal ganglia react more strongly when a reward signal is present. When the striatum is damaged, animals will still learn to choose for responses that will bring a higher reward. However, the animals will not react as strongly as they did before the damage.

Movement and Diseases

Parkinson’s disease

Parkinson's disease is characterized by slow movements, shaking, rigidity, and difficulties in mental and physical activities. Many patients are also depressed and have impairments in memory and reasoning. In the age class +65 years approximately 1-2% have the disease. Researches have been curious about what determines the speed of movements. According to one hypothesis we balance between speed and accuracy. The symptoms of Parkinson's disease does not support this theory. In Parkinson's disease many neurons die, especially in the substantia nigra. This causes the lack of dopamine, which causes excessive inhibition of the thalamus and decreased excitation of the cerebral cortex. Normally people lose about 1% of the neurons in substantia nigra per year after the age of 45. Impairment of 20-30% neurons start Parkinson's disease symptoms. However, individual differences are huge again, and the disease can have early-onset or late-onset. In the cell level the damage in Parkinson's disease takes place in the mitochondria. Heritability of Parkinson's disease is low. The effect of genes is greater in early-condition Parkinson's disease. Some toxins can destroy cells in the substantia nigra and therefore increase the risk of Parkinson's disease. For example herbicides and pesticides are known to cause the disease. L-dopa (a precursor of dopamine) is the most common treatment for Parkinson's disease. Dopamine itself is not efficient because it would not pass the blood-brain barrier. However, L-dopa does not work for every patient, it does not stop the neurons dying, and it has some nasty side effects (e.g. nausea, sleeping problems and hallucinations). Also other treatments are suggested, e.g. neurotrophins, antioxidants, dopamine receptor stimulants, electrical stimulation in certain brain areas, apoptosis decreasing drugs etc. Also, the transplantation of brain tissue from aborted foetuses is an option. Patients have the chance to live longer, but this methods is difficult and expensive. The use of foetal tissue that is genetically modified and made out of stem cells will supposedly decrease the problems. However, the results are moderate.

Huntington’s disease

Huntington's disease is a disease that affects muscle coordination and leads to cognitive decline and dementia. Usually it starts with tremors, which later start to affect walking, speech etc. Also psychological symptoms are present: depression, drug abuse, alcoholism, sexual problems, sleep disorders and anxiety. Sometimes psychological symptoms start before physiological and therefore the patient can be misdiagnosed. Usually Huntington's disease starts at the age 30-50. However, the disease is relatively rare. Huntington's disease is characterized by brain impairments in the caudate nucleus, putamen, and globus pallidus. The disease is controlled by an autosomal dominant gene. Everyone has a protein huntingtin which is essential, but its mutant form causes Huntington's disease when occurring in the brain. Researchers have found a gene related to Huntington's disease. A sequence of bases C-A-G (cytosine, adenine, and guanine) determines the likelihood of the disease, as well when it might strike. People with more repeats of those bases have an earlier onset. Several treatments are suggested. Some medicines block the forming of clusers in the glutamine chains. Other medicine interferes with the RNA part that enables the expression of the disease. Neurotrophins will probably be effective, if we find a way to get them into the brains. Tetrabenazine reduces the squirming of the body, thanks to dopamine. Another treatment looks into sleep. Research with mice has shown that mice with a mutation of Huntington’s disease slept and learned better after a daily sleeping pil.

What is sleep and why is it important for the human brain? - Chapter 8 (12)

Rhythms of Sleep

The body has an innate rhythm of sleep and wakefulness. This rhythm is self-generated.Endogenous circannual rhythm refers to innate rhythm for seasonal changes.

Endogenous circadian rhythm refers to innate rhythm that lasts approximately a day. The rhythm can be altered moderately, but major abnormalities from the 24-hour norm do not work out.

People vary in their circadian rhythms (morning people/evening people). Circadian rhythm also changes as a part of aging; children prefer to go to bed early, adolescents later, and at the age of 20 people start to feel sleepy earlier and earlier.

Free-running rhythm refers to a rhythm which is not interfered by any stimulus.

The circadian rhythm is reset by zeitgebers ("time-giver" in German). Light is the major zeitgeber, as also noise, meals, temperature and exercise function as zeitgebers.

Blind people either adopt free-running rhythm or set their rhythm to stimuli other than light.

Jet lag is a condition which results from alterations to the body's circadian rhythm; circadian rhythm is either phase-delayed or phase-advanced. Jet lag results from rapid crossing of time zones, and the symptoms can vary from sleepiness to depression and problems in concentration. Jet lag causes greater stress to some people than to others. During stress a hormone called cortisol is secreted, and in a long run it can result in impairments in the brain and memory. Adjusting to night shifts is rather difficult for many people. Those people working at nights have more accidents than day-shift workers. Circadian rhythm is a robust mechanism, which is not easily changed.

Suprachiasmatic nucleus

The suprachiasmatic nucleus (SCN) is responsible for setting the circadian rhythms of sleep and temperature. This process happens naturally by genetic control.

The SCN is located above the optic chiasm. The pathway from retina to SCN is called retinohypothalamic path. The retinal ganglion cells on that path have their own photopigment, melanopsin. The ganglion cells react directly to light, even when they don’t receive input from the rods and cones. The ganglion cells react on the average amount of light, not on sudden changes in light and they don’t contribute to vision.

The biochemical basis of the biological clock is based on certain genes. Genes called period and timeless produce proteins called per and tim. Light increases the production of per and tim, which increase the activity of the suprachiasmatic nucleus. Gene mutations in period and timeless can make the circadian rhythm longer or shorter. The proteins per and tim are available in small amounts at the beginning of the day and the amount increases during the day. In the evening, the amount of these proteins is high and the animal will go to sleep. The production of these proteins will then stop and the concentration of these proteins will decrease to the amount of the beginning of the morning. This is the moment that the cycle begins again.

The superchiasmatic nucleus regulates several brain areas, for example the pineal gland. The pineal gland is an endocrine gland releasing the hormone melatonin, which controls circannual and circadian rhythms. Melatonin is secreted during night. Melatonin pills are used as sleeping pills.

Stages of sleep and brain activities

Sleep is a state that is produced actively by the brain and it is characterised by a decrease in brain activity and reaction to stimuli.

Coma is a state of unconsciousness, in which a person cannot be awakened and fails to respond normally to any stimuli. It is caused by stroke, disease or damage in the head. A person in a vegetative state shows partial arousal instead of true awareness, without purposeful activities. A person in a minimally conscious state can have moderate purposeful activities. Both states can last for months or even years. Brain death is a condition in which all the brain activity ends.

Polysomnography is a method combining EEG and eye-movement recording.

Stages of sleep:

Stage 1: irregular, low-voltage waves. Brain activity is less than during wakefulness.

Stage 2: K-complexes (high-amplitude waves) and sleep spindles (12-14Hz waves in a burst).

Stages 3 & 4: slow-wave sleep (SWS), large-amplitude waves.

Stage 5: rapid eye movement (REM) sleep or paradoxical sleep. Increased brain activity, relaxation of muscles, irregular heart rate and breathing.

Stages 1-4 are also known as NREM sleep (non-REM).

Dreams are usually seen during REM sleep, but also in other sleep stages.

The sleeping process goes through stages 1-4, then back to 3 and 2 and then to REM. This cycle lasts about 90 minutes and is repeated again. REM sleep is most common in the morning.

Brain mechanisms

The midbrain is an essential structure for maintaining wakefulness. Also pontomesencephalon (part of the reticular formation) is important for cortical arousal. The locus coeruleus improves the recollection of recent memories and increase wakefulness. It stays inactive during sleep. Activation of the pons precedes the REM phase. The pons originates PGO waves (pons-geniculate-occipital) during REM sleep, and it also relaxes large muscles.

Interaction between neurotransmitters serotonin and acetylcholine is essential for REM sleep.

One of the pathways of the hypothalamus releases neurotransmitter histamine. It has excitatory influences, so it is released during arousal. Another pathway from hypothalamus releases neurotransmitter orexin (aka hypocretin). It is essential for maintaining wakefulness. Some of the axons from the basal forebrain release acetylcholine which also increases arousal. GABA is essential for sleep, as it inhibits synapses.

Sleeping disorders

Most adults need approximately 8 hours of sleep per night. However, individual differences are huge. Insomnia refers to sleeping difficulties. Insomnia is caused by several reasons including noise, too hot or cold environment, pain, stress, (mental) disorders (depression and Parkinson’s disease), medications etc. Prolonged use of tranquilizers or alcohol can also cause insomnia, since the person is not able to fall asleep without those substances. Some cases of insomnia are related to changes in the circadian rhythm. People with a phase delayed rhythm have a hard time falling asleep and have trouble waking up. Someone with a phase advanced rhythm falls asleep easily, but wakes up early.

Sleep apnoea

Sleep apnoea is a type of insomnia which is characterized by interruptions in breathing while sleeping. As a consequence the sleep is disjointed, people suffering from sleep apnoea experience sleepiness and depression. People with sleep apnoea have lost neurons in different brain areas and because of this, they show deficits in learning, reasoning, attention and impulse control. Hormones, genetics and obesity affect sleep apnoea. Patients are told to lose weight and avoid alcohol and tranquilizers.

Narcolepsy

Narcolepsy is a chronic sleep disorder characterized by excessive daytime sleepiness. Other symptoms are cataplexy (sudden muscle weakness), hypnagogic hallucinations (dreamlike hallucinations which can be difficult to identify as dreams) and sleep paralysis (inability to move during sleep). Narcolepsy is related to lack of neurotransmitter orexin. People with narcolepsy have a few cells in the hypothalamus that produce and release orexin. Orexin stimulates cells that release acetylcholine, which enhances arousal and vigilance.

Night terrors, sleepwalking and talking in your sleep

Night terror refers to experiences of extreme terror and anxiety during NREM sleep. It is more common in children than adults.

Talking while sleeping is common among people in any age, while sleepwalking is more common among children. Sleepwalking can be dangerous, but it is not dangerous to wake up a person who is sleepwalking. Sleep walking can be more common in some families than in other. It usually doesn’t go together with dreaming and it usually occurs in phases 3 and 4 of sleeping. Sexsomnia is a condition in which person either masturbates or has sex with her or his partner while sleeping and doesn’t remember this afterwards.

Functions of Sleeping

While sleeping, the body rests its muscles, rebuilds proteins, reorganize synapses and decreases metabolism. For these reasons sleep is essential for us. All species sleep.

Hibernating animals save energy while food is scarce. Hibernation slows the aging process significantly. One hypothesis is that the original function of sleep was preserving energy. Throughout evolution, more functions were added to sleep. Sleep enhances memories. When people learn something and go to sleep, their memory will enhance in comparison to the moment before they went to sleep. Sleep helps to reorganize memories. It seems that the brain keeps repeating certain experiences during sleep, which strengthens these memories. Sleep also strengthens memories by omitting less successful connections. Other synaptic connections are strengthened. Sleep spindles are related to learning, as they indicate the information exchange between the thalamus and cerebral cortex. Learning increases sleep spindles, and there is high correlation between nonverbal IQ test results and the amount of sleep spindles.

The more hours of sleep in total, the higher the percentage of REM sleep. The length of NREM varies less. NREM sleep is more related to verbal learning, and REM sleep to learning of motor skills. MAO inhibitors (used as antidepressants) decrease REM sleep. However, they do not seem to impair memory. According to one theory, eye movements during REM increase the oxygen supply to the cornea. The truth about the function of REM sleep still stays unknown.

There are different hypotheses on the function of dreaming. The activation-synthesis hypothesis states that the function of a dream is to give meaning to disturbed information. This hypothesis also states that when you dream about flying or falling, it’s because your body is in another position than during the day and your brain feels vestibular sensation and interprets this as flying or falling. The clinic-anatomical hypothesis states that dreams are a way of thinking during special circumstances. Pictures are produced, without the interference of the senses. The motor cortex and the activity in the prefrontal cortex is supressed, which won’t result arousal to turn into action. Internal and external stimulation activates parts of the parietal, occipital and temporal cortex. There is no sensory input, so hallucinating perceptions are formed. Both theories are difficult to test and they are rather vague.

How does the human body regulate temperature, thirst and hunger? - Chapter 9 (12)

Temperature

Several studies on animals and humans indicate the necessity of temperature for behaviour, learning, development etc. Homeostasis refers to biological processes which keep the body in a stable, constant condition. The body has a range within values have to fit, usually this range is so narrow that it is also called a set point. For example blood levels of oxygen, glucose, sodium chloride, protein, fat and acidity need to be stable. Set points can have seasonal changes, for example many animals increase their body fat before cold winter. The term allostasis refers to this adaptive mechanism the body uses to change its set points.

Negative feedback is a process that reduces alterations from the set point. Maintenance of homeostasis (basal metabolism) consumes a lot of energy: approximately 2/3 of total energy consumption. If an animal is poikilothermic, its internal temperature varies considerably. These animals don’t have physiological mechanisms (like sweating) to regulate their temperature and they are dependent on their own behaviour to change. It is the opposite of a homeothermic animal which maintains thermal homeostasis. Humans, as most of the other mammals, are homeothermic, we generate heat in respect to our total mass and radiate in respect to our surface area. Reptiles and fish are poikilothermic.

We have two kinds of mechanisms to control body temperature:

  1. Behavioural: putting more clothes or taking them off, cuddling with other people or animals or other warm objects, increasing or decreasing activity.

  2. Physiological: when hot, we sweat. (Other animal can also pant or lick themselves). When cold, we shiver, decreasing blood flow in the skin.

The advantage of being homeothermic is that we are able to be active even when the weather is cold. A warmer animal also has warmer muscles, and they can therefore run faster and are less likely to be fatigued. However, when the temperature rises above our normal temperature (37 degrees), it costs us more energy.

The brain areas which are related to the control of body temperatures are in and around the hypothalamus. These areas are called preoptic area/anterior hypothalamus (or POA/AH) and they send output to the raphe nucleus in the hind brain, that regulates physiological mechanisms. If these areas are cold an animal acts like the environment is cold even though it was warm. Fever is the immune systems mechanism to slow down the growth of bacteria and enhance its own activity. Leukocytes (white blood cells) of the immune system release cytokines which activate the hypothalamus to release prostaglandins. Prostaglandins are essential for fever. In fever the set point changes. If the fever is too high, it can also be dangerous: 41°C is life-threatening. In that temperature proteins start to shatter. Reproductive cells need a slightly cooler environment than the normal 37°C: this is the reason why men have testicles.

Thirst

70% of our body is water.In the case of dehydration the body has several autonomic responses to control its homeostasis, like producing more concentrated urine and decreasing sweating. When there is a shortage of water, the posterior pituitary gland releases the hormones vasopressin and antidiuretic hormone. Vasopressin (also antidiuretic hormone or ADH) and angiotensin II are hormones which constrict the blood vessels and thus increase blood pressure.

Two types of thirst are:

  1. Osmotic thirst, which is caused by changed concentrations (eating salty things).

  2. Hypovolemic thirst, (referring to low volume) which is caused by the loss of water (e.g. excessive bleeding or sweating).

Osmotic pressure is caused by differences in the concentration inside and outside the membrane. A semipermeable membrane allows water to pass freely but not solutes. After eating something salty, sodium ions will increase in the extracellular fluid but not in the intracellular fluid. This condition draws water into the extracellular fluid and causes osmotic thirst. Some neurons detect the loss of water and they trigger osmotic thirst, which will result in the normal state again. Brain areas that detect osmotic pressure are OVLT (organum vasculosum laminae terminalis) and SFO (subfornical organ). These areas are dependent on different areas of the hypothalamus (like the paraventricular nucleus, PVN). The stomach has also some receptors for detecting sodium levels. These different areas are connected to parts (e.g. supraoptic nucleus and paraventricular nucleus) which control the release of vasopressin. The digestive system has detectors which prevent over-drinking. You know when to stop drinking, because your body monitors how often you swallow and it also monitors the dilution of the stomach and the upper part of the small intestine. When you lose much body liquid from sweating, bleeding or diarrhoea, your body will activate hormones that constrict blood vessels (vasopressin and angiotensine II). When your blood amount decreases, the kidneys release the enzyme renin, which goes together with the formation of angiotensine. Angiotensine changes other enzymes into angiotensine II, which will result in more blood vessels constricting and a higher trigger for thirst.

Sodium-specific hunger is caused by the lack of salt and it is a strong preference for salty taste. It is increased by angiotensin II. It often occurs in people who did sports or menstruating women.

Hunger

Animals have different eating habits. Some eat a lot occasionally, some only what they need at the time. Habits of humans are somewhere in between the extremes. The digestive system works to break the food down into a form that cells can use. The enzymes in the mouth start to break down carbohydrates, food goes to the esophagus and stomach where the enzymes in the stomach start to break down proteins, then food goes to the small intestine where the enzymes break carbohydrates, proteins and fats.

Lactase is an enzyme breaking lactose (milk sugar). Some populations have the enzyme and some do not For example, it is more common in Scandinavia than Asia. Lack of the enzyme causes stomach cramps and gases when dairy products are used. People who are lactose intolerant can drink a little amount of milk and a bigger amount of cheese and yoghurt (because these are easier to digest). However, they learn to limit their intake.

Carnivores (meat eaters) get all the nutrients rather easily. Herbivores (plant eaters) and omnivores (meat and plant eaters) have to plan their diets more precisely.Not all food is eatable. We have several mechanisms to detect eatable food, such as taste receptors, learning from experience, and from others. We start to like tastes more when we try them multiple times. Conditioned taste aversion is a phenomenon which occurs when a taste is linked to illness: we start to dislike it. Eating is not only fulfilling the biological needs, most of the people also like to eat and chew. However, a taste alone does not always leave an individual satisfied. Stomach distention is the signal which stops us eating. The vagus nerve sends information about the stretching of the stomach walls and the splanchnic nerves sends information about nutrients.

Also signals from the duodenum (part of small intestine) report about the satiety. Food in the duodenum causes secretion of cholecystokinin (CCK) which closes the sphincter muscle between the stomach and the duodenum and stimulates the vagus nerve.

Glucose is the main source of energy. Glucose level stays quite stable over times because of the body’s control mechanisms. Two pancreatic hormones regulate glucose level:

  1. Insulin, which helps glucose to enter the cells. When the insulin is high, glucose can easily enter the cell. High levels of insulin decrease the appetite.

  2. Glucagon, which activates the liver to convert its glycogen into glucose. This will act as a supply in the blood.

If the insulin level is constantly high or low, a person increases eating. Low insulin level (as people with diabetes) causes the condition in which cells do not get glucose. A high level of insulin causes the opposite condition in which the glucose is pumped into the cell rapidly and blood glucose level remains low. Insulin is an example of short-term regulation.

A chemical called leptin is responsible for long-term regulation. It is produced by fat cells. A high leptin level causes overall activation, increases the activation of the immune system and decreases hunger. Leptin also triggers the puberty in the adolescence. Usually overweight people have already high leptin levels, so leptin does not work as a drug if they want to lose weight. It seems like overweight people are less sensitive to leptin than some other people.

Brain mechanisms

The arcuate nucleus of the hypothalamus is an essential area for controlling appetite. It has neurons which are sensitive to hunger information and neurons which respond to satiety. The neurons responding to hunger receive information from the taste pathway and from axons releasing neurotransmitter ghrelin. Ghrelin is the hunger hormone and it is released during periods of food deprivation, which triggers the contraction of the stomach. Ghrelin also has an influence on the hypothalamus: it decreases the appetite. Also, it enhances learning in the hippocampus. The neurons responding to satiety respond both to short-term and long-term regulation systems.

The paraventricular nucleus (PVN) is an important area for the feeling of satiety. Receptors in the paraventricular nucleus (melanocortin receptors) send signals when it is time to stop eating. Transmitters neuropeptide Y and agouti-related peptide block the satiety actions of the paraventricular nucleus and can cause overeating. Also orexin (familiar from narcolepsy) is a chemical which controls appetite. It enhances the persistence of an animal to seek food and it reacts to rewards. When orexin-receptors are blocked, an animal will be less active and less willing to work for a reward.

The lateral hypothalamus has several roles in eating. It controls insulin secretion by stimulating the pituitary gland (the pituitary gland releases hormones that enhance the release of insulin), alters taste responsiveness (when the lateral hypothalamus detects hunger, it sends out messages to have food taste better) enhances swallowing and controls autonomic responses (e.g. secreting digestive enzymes).

Ventromedial hypothalamic syndrome is caused by a damage to the ventromedial hypothalamus. It leads to overeating and weight gain. A person with this kind of syndrome eats normal-size meals, but more often (because their stomachs empty faster than normal and an increase in insulin production).

Eating disorders

Nowadays, we have more food than we had ever before and a lot of people are overweight. Therefore, much research is conducted into why some people become obese and others do not. People used to be afraid of not getting enough food, but nowadays we are afraid to be obese. Researchers wonder how it’s possible that two people, who have access to the same amount of food, differ in weight.

Obesity is a severe problem in Western societies. Social, psychological and physiological factors are all to blame. Some mutated genes affect obesity. For example, the melanocortin receptor can be impaired. Syndromal obesity refers to a state in which obesity is caused by a syndrome or other medical condition. Environmental factors also make a difference. Working life has changed, sedentary work is common nowadays. In the US, obesity is classified as a disease. It’s quite often the case that fat parents have fat children and thin parents have thin children. Research has looked at the relationship of weight between adopted children and their biological and adoptive parents. The results showed that the weight of those children correlated more with the weight of the biological parents, than with the weight of the adoptive parents. Some use this as an argument for a genetic influence on obesity, but it can also be used as evidence for a prenatal influence on obesity. People used to think that obesity and psychological stress went hand in hand. In movies you can often see sad people eating ice-cream (or other sweet things). However, according to research, mood has a weak relationship with weight gain. The best treatment for obesity is a change of lifestyle: more exercise, less food (or, better quality food). However, most people find it difficult to maintain a reduction in weight.

In general people who drink soft drinks are more obese. Soft drinks contain fructose which does not increase insulin level and therefore does not give the feeling of satiety. Diet soft drinks can cause obesity even more than normal soft drinks. Also drugs are used in the fight against obesity. For example fenfluramine, phentermine and sibutramine are commonly used. In extreme cases of obesity surgery can be used. Decreasing stomach size is the most common method.

In anorexia nervosa, an individual refuses to eat. Usually the disease strikes at adolescence. The mechanism behind anorexia is psychological; the person fears becoming fat. The triggers of anorexia are not well understood. Bulimia nervosa is a disease in which the individual engages both in overeating and extreme dieting. Some bulimics vomit after eating, trying not to gain weight. Most bulimic sufferers also have another psychiatric disorder. 95% of the bulimic sufferers has a depression, anxiety or other emotional problems. Bulimia is more common nowadays. People with bulimia have an increased production of ghrelin (associated with a higher appetite). This can be seen more as a result than as a cause.

Bulimia has been compared to drug addiction (the cycle of dieting and eating). Eating delicious food activates the same brain areas as an addictive drug. Drug addicts who can’t get drugs, often go and eat too much. People who don’t have a lot of food have a higher chance of becoming drugs users than people who have enough food.

How can hormones influence sexual behaviour? - Chapter 10 (12)

Sex and Hormones

Sexual differentiation begins in the chromosomes. During the early stages of prenatal development, both men and women have a set of channels of Müller (this will eventually become female internal structures) and channels of Wolff (this will eventually become male internal structures). They are sometimes also called Wolfferian ducts and Müllerian ducts. All humans have also primitive sex glands that will become either ovaries or testes. A man has a Y-chromosome, which contains the SRY-gene. This gene enables the primary sex genes to develop into testes. The developing testes produce androgens, which helps the testes grow more and the testes will again develop more androgens, and so the cycle continues. Androgens enable the channels of Wolff to develop into seminal vesicles and vas deferens.

The Müllerian inhibiting hormone, MIH, is a peptide hormone which enables the degeneration of the Müllerian ducts. This results in the development of the penis and the scrotum. Women don’t have the SRY-gene and therefore their sex glands develop into ovaries. The Wolfferian ducts degenerate and the Müllerian ducts develop into the vagina, fallopian tubes and uterus. Estradiol and oestrogen cause certain changes in the development of the brain and other internal sexual organs.

Our nervous system communicates between synapses. To deliver a message at a bigger distance, our body uses hormones. A hormone is a chemical substance that is distributed by glands and that makes is way through our blood to reach other organs and influences our functioning. A gland that produces a hormone is called an endocrine gland. There are different types of hormones.

Steroid hormones are derivatives of cholesterol. They have several effects:

  • Cause rapid effects by binding to the membrane.

  • Activate certain proteins.

  • Either activate or inactivate certain genes by binding to chromosomes.

The sex hormones are also steroids, but they are somewhat special. They can be divided into three categories:

  1. Androgens, or so-called male hormones (testosterone)

  2. Estrogens, so-called female hormones.

  3. Progesterone, also a female hormone. Secreted during pregnancy. It prepares the uterus for pregnancy and preserves the pregnancy.

Sex-limited genes control the differences between men and women. In the brain they control apoptosis, making some areas larger in other sex. Sex hormones have an influence on the brain, genitals and other organs.

Effects of hormones

The sex hormones have two kinds of effects:

  1. Organizing effects, which influence whether the body will develop male or female characteristics: they take place before birth.

  2. Activating effects, which refer to temporary activations caused by a hormone: can take place any time.

Organising effects

Organising effects during a sensitive period decide whether an embryo becomes male or female. The amount of testosterone determines the differentiation of external genitals and certain aspects of brain development. A high amount of testosterone will result in a male pattern, a low amount will result in a female pattern. Estradiol has a large effect on the internal genitals, but a small effect on the external genitals. Without testosterone in an early stage of development, an individual will become female, but without estradiol during the early sensitive stage, there will be no complete female development.

Sex differences in the brain

Sex hormones also affect the hypothalamus, amygdala and some other brain areas. The hormones cause physiological and anatomic differences between sexes. The sexually dimorphic nucleus (SDN) is a part of the hypothalamus which controls sexual behaviours in men. Parts of the female hypothalamus can release a pattern of hormones periodically, like in the menstrual cycle. Men can’t do that and women who have been exposed to much testosterone early in life, can’t also do that. On the hypothalamus, testosterone works as an organizer. Sex hormones influence behaviours temporarily. Behaviours, in turn, also influence hormonal secretion. However, while hormones do not cause sexual behaviours, they still activate them by enhancing sensations. Sex hormones prime certain brain areas (e.g. the medical preoptic area, MPOA) to release dopamine. Dopamine increases sexual activity. Decreased sex hormone levels can result in memory impairments. Even though low testosterone levels on men decrease sexual interest, it does not cause impotence. Impotence is usually caused by a deteriorated blood circulation. Drugs, psychological tension and neurological conditions can also cause this.

Sex differences in child behaviour

Prenatal hormones can contribute to the differences in behaviour in children. We all know that most boys love to play with cars and girls with dolls. Some children have a stronger preference for boyish or girlish activities and their preference stays consistent. Children who show the greatest preference for guy activities at the age of 3, will also prefer guy activities when they are 13. The same can be said for girl activities. A partial causation for this is socialisation. Most parents give their sons other toys than they give their daughters. Predispositions also play a role: research has shown that female babies aged three to eight months preferred dolls over trucks. The same showed to be true for apes. It’s possible that the different sexes are born with a different preference in toys. However, girls mature faster than boys and the difference might be caused because the boys can’t really show a true preference at that age.

Research has also shown that girls who have been exposed to a higher level of testosterone in the uterus, showed a preference for boy toys. Prenatal hormones (especially testosterone) change the brain in such a way, that it influences the preference of girls and boys in activities and toys. Education and upbringing also play a role. When children show a preference for a certain type of toys, parents will buy more of these toys and will in this way enhance the preference for these toys. This is called the multiplier effect.

Activating effects of hormones

In all periods of life there are activating effects. These will modify the behaviour temporarily. Changes in hormonal secretion can influence sexual behaviour within 15 minutes. Behaviour can influence hormonal secretion as well. Hormones don’t cause sexual behaviour, they change the activity in different brain areas, which lets the brain react differently to certain stimuli.

Oxytocin is a hormone secreted by the pituitary gland. It is responsible for the contractions of the uterus during labour and the milk release from the mammary gland. It is also possibly important for the bonding between mating partners and a mother and her child. Parenthood changes both the secretion of hormones and the pattern of hormone receptors. Hormonal changes help mothers to focus on their babies. Nevertheless, hormones are not necessary for parental behaviour (adoptions!). Vasopressin is an important hormone for the bond between partners. It increases the commitment to the parenthood

Men

Testosterone is essential for male sexual arousal. It enlarges the touch sensitivity in the penis. Like mentioned before, testosterone enables the MPOA to release dopamine. MPOA neurons release much dopamine during sexual activities. In average concentrations, dopamine stimulates the D1 and D5 receptors. These enable a man to get an erection. When there is more dopamine in the body, the D2 receptors will be stimulated and these enable a man to get an orgasm. Dopamine stimulates sexual activity and the neurotransmitter serotonin blocks the release of dopamine. You can also see this in anti-depressants: one of the side-effects is a decreased sexual arousal.

The level of testosterone correlates positively with the sexual arousal of men and their interest to search for a sexual partner. Research has shown that married men and men who are in a committed relationship and living together with their partner, have a lower level of testosterone than men who are single and have the same age. Two explanations for this phenomenon can be found: marriage leads to lower levels of testosterone, because married men don’t have to fight for sexual partners and another explanation is that men with a lower level of testosterone have a higher chance to get married and stay married. Evidence has been found for both explanations. Research has also found that single women have more testosterone than women who are married. One study has shown that both men and women with higher levels of testosterone are more prawn to find a second sexual partner, even if they are married.

Women

The menstrual cycle of women lasts approximately 28 days, and it is produced by the ovaries, hypothalamus and pituitary gland. At the end of the menstrual cycle, follicle-stimulating hormone (FSH) is secreted. It influences the growth of a follicle in the ovary. Together with luteinizing hormone (LH) FSH causes the release of the follicle. The remainders of the follicle (corpus luteum) release progesterone and this hormone prepares the uterus for the implantation of the ovum. Progesterone stops the secretion of LH. When the ovum is fertilized, the levels of progesterone and estradiol rise during pregnancy. When the ovum is not fertilized, the cycle begins again. A consequence of high progesterone and estradiol levels during pregnancy, is the fluctuating activity of the serotonin 3 receptor. This causes nausea. Pregnant women become more nauseous because of the high activity of that receptor.

Birth-control pills are used to prevent pregnancy by interfering with the normal feedback cycle of the ovaries and pituitary gland. Usually birth-control pills are combination pills containing oestrogen and progesterone. The higher progesterone and oestrogen levels stop the release of FSH and LH.

Women are more sexually active during the periovulatory period (the middle of the menstrual cycle). They also find more masculine men more attractive.

Effects of sex hormones on non-sexual traits

Men and women differ in more than one way from each other. Almost all those changes vary per culture and people often exaggerate the differences between the two sexes. However, some trends are consistent. Prenatal oestrogen and androgens influence many aspects of the brain, including which neurons survive and which synapses will be formed. Both androgens and oestrogens stimulate brain areas that are important for memory. Some brain areas are relatively bigger in men than in women. This is not caused by the bigger posture of men. However, most people have typical male patterns in one brain-area and female patterns in another area. Differences in brains shouldn’t be related to differences in behaviour. In most cases, the relation between brain differences and behaviour is based on speculation.

Variations in sexual behaviour

Most people are not aware of how much diversity exists in sexual behaviours. When it comes to animals, many sex differences have a function in terms of evolution. Evolutionary psychologists have suggested several differences among humans.

According to these theories, men can succeed by using either of two strategies:

  1. Concentrating on one woman and offering her resources.

  2. Mating with many women, when some of them might be able to raise their children without a man’s resources.

However, women can only become pregnant rather seldom, so for them it is better to focus on the quality rather than the quantity of mates. This explanation is one possible reason for men’s desire for many sexual partners. On the other hand, women can also benefit from several partners: other men can offer better resources or children if her husband is infertile. Both men and women value intelligence, honesty and attractively in a potential partner. Additionally women value wealth, success and good smell. The latter is explained by women smelling their potential mates immune systems - it should not be too similar (otherwise, it might be a relative and you do not want to marry a cousin). In many societies men have a preference for a younger partner. Possibly the explanation is that younger women have a longer period of fertility.

According to one hypothesis, men are more jealous of women’s sexual infidelity, and women are more jealous of men’s emotional infidelity. From the evolutionary perspective this seems plausible, but studies have suggested that both men and women suffer more by their partners emotional attachment towards another person. Similar results in cross-cultural studies are not proof of an evolutional root. It is often difficult to determine what is a result of evolution and what is learned. We also have to note that no gene forces us to behave in a certain way.

Sex identity

The term sex refers to biological aspects of men or women, whereas gender is related to people’s ideas about sexes. Some people feel their sex is not consistent with their gender. Intersexes are people who have anatomies intermediate between men and women. This can result from gene mutations or atypical hormone levels. The most common cause is congenital adrenal hyperplasia (CHA), in which the adrenal glands are overdeveloped, causing higher testosterone levels than usual.

Men with lower levels of testosterone can develop more feminine and women with higher levels of testosterone can develop more male than people with average levels. Hermaphrodites are people with characteristics of both men and women. A real hermaphrodite has testes on one side of the body and ovaries on the other side, or a mix of testes tissue and ovary tissue on both sides of the body.

Genetic women with CAH are raised as women. Their brains were exposed to high levels of testosterone during the pregnancy and after birth. Most children with CAH have a preference for male toys. Most parents encourage these children to play with female toys. Studies have shown that adults with CAH have interest that lie between those of male and female.

Testicular feminization (or androgen insensitivity) is a condition in which a person has an XY chromosome pattern but genitals like females. Cloacal exstrophy is a condition in which a male is born with a smaller penis due to impaired pelvis development. Previously these individuals were raised as girls too, but even after surgeries they often adopt a more masculine identity. Many individuals who underwent a surgery because of abnormal penis or clitoris in the childhood are dissatisfied later in life. The conclusion: both hormones and the method of raising have significant effects on a child.

Sexual orientation

Some humans as well other animals show homosexual tendencies. A genetic disposition is greater in men than in women. Men tend to be aware of their homosexuality earlier than women.

Homosexuals differ from heterosexuals in several ways:

  1. Heterosexual men have longer arms and legs on average (homosexual women have longer arms than heterosexual women).

  2. Heterosexual men have bigger right hemispheres than homosexual men.

  3. Homosexuals differ in many behaviours not directly linked to sex.

Sexual orientation is not just random decision, but more a complex issue with many affecting factors. Researchers haven't found any certain gene related to homosexuality yet. Still they have noticed that some genes are more common in homosexuals than heterosexuals. Homosexuality seems to have a genetic basis, at least to some degree. Studies with twins have shown that when one monozygotic twin was homosexual, the other twin was in 31% of the cases also homosexual. With dizygotic twins, this was 8%. Homosexual relatives of homosexual men are more common from the mother's side. This fact suggests that a gene related to homosexuality is on the X chromosome.

Genes related to homosexuality cause a problem for the evolutionary perspective: why do those genes survive? Several possibilities have been suggested:

  1. Kin selection. Homosexuals might help their sisters and brothers to rear their children, which helps the genes to be passed on.

  2. The genes behind homosexuality can be beneficial for females

  3. The gene in homozygous form might lead to homosexuality, and the heterozygote form might lead to benefits in reproduction in heterosexual men.

  4. Homosexuality might activate or deactivate certain genes.

Hormone levels in heterosexual and homosexual adults seem to barely differ. It seems that sexual orientation is determined by prenatal hormones. It’s possible that testosterone levels in the sensitive period (2,5 to 5 months) of pregnancy play a role in sexual orientation. The immune system of the mother can also have prenatal effects. Some studies (not all) have shown that boys who have older brothers, have a higher chance to become gay. This isn’t caused by the social environment, but by the amount of boys the mother has born. The mother’s immune system can react on certain proteins and attack the sons in a way that alters their development. That is the way in which the mother’s immune system can have prenatal effects. The mother’s stress and alcohol use during pregnancy can also have effects. Research with rats has shown that prenatal stress can influence sexual development. Stress releases corticosterone and endorphins and these decrease the effects of testosterone. The nervous system of a man will look more like the nervous system of a woman because of this. One study showed that mothers of homosexual men had more stress during pregnancy than mothers of heterosexual men.

What are emotions (biologically)? - Chapter 11 (12)

Defining Emotion

Emotion is a difficult concept to define as we can’t easily observe it. Emotion is usually shattered into three components: cognitions, feelings and actions. Emotional situations affects the autonomic nervous system (the sympathetic and the parasympathetic). Every situation arouses the autonomic nervous system in a different way. Usually, the parasympathetic and sympathetic nervous system are active at the same time, but one is sometimes more active than the other. The sympathetic part prepares the body for fight or flight situations. Basically, it’s for quick reactions. The sympathetic part reacts when a person interprets a situation as dangerous or threatening. Not everyone will react on the same stimulus in the same way, because every person interprets a stimulus in his/her own way. The sympathetic part stimulates organs that are important for fight or flight reactions, like the heart, and it inhibits activities that can wait until later on, like the stomach or intestines.

The parasympathetic part is for relaxation and maintenance. This part is responsible (among others) for digestion. When a stimulus that has been interpreted as threatening activates the sympathetic part and then suddenly disappears, the parasympathetic part will become more active.

Emotions and theories

It is usually assumed that first we feel an emotion and then we give a physiological response to it. James-Lange theory suggests that first comes the physiological response, and the emotion is a response to it. Described be different components, James-Lange theory claims that the order is 1. The cognition, 2. The action and 3. The emotion. According to James-Lange theory we need to conclude that a person without strong physiological response should feel less emotions, likewise a person with strong response should feel more.

Some people have a condition called pure autonomic failure (also called the syndrome of Bradbury-Eggleston), in which the autonomic nervous system is impaired. These people should not feel emotions, according to James-Lange theory. However, these people report feelings, but they also report having less intense feelings than before. These people probably refer to the cognitive aspect of emotions, they don’t really feel the emotions. Their diminished emotional feeling is consistent with the James-Lange theory.

The prediction of the response of the autonomic nervous system is situationally dependent. Researchers have found evidence that smiling increases happiness. However, smiling is not necessary for happiness, for example people with Möbius syndrome (disability to move facial muscles) do experience happiness.

Brain areas related to emotions

The limbic system (areas of the frontal brain that surround the thalamus) is an essential brain area for emotions. A large part of the cerebral cortex also reacts on emotional situations. Researchers have studied emotions by measuring evoked responses, and using PET and fMRI techniques. Researchers are not only trying to study which brain areas are responsible for emotions, but they are also trying to determine which area is responsible for a specific emotion. Disgust in the only emotion that might be located in a certain part of the brain (in the insular cortex). All other emotions seem to have cells responding to them all over the brain.

Jeffrey Gray (1970) created a hypothesis about two competing systems:

  1. Behavioral activation system (BAS) is linked to left hemisphere activity, causing low or moderate autonomic arousal, with happiness or anger.

  2. Behavioral inhibition system (BIS) is linked to right hemisphere activity, causing arousal, increased attention and inhibits actions. Activates emotions such as fear and disgust.

People with a more active frontal cortex of the left hemisphere are prone to be happier and more outgoing. The right hemisphere is better at both expressing emotions and decoding other people’s emotions. Localization is so strong that when the right hemisphere is inactive people do not feel strong emotions and do not remember the emotional contents of previous situations.

Emotions have different functions. Fear is a sign that something is threatening us, anger helps us to attack and disgust tells us when to avoid something that might be harmful. Emotions can also be useful at the moment of quick decision. Emotions are also present when we are making moral decisions. We are able to imagine how other people feel. We tend to decide first, based on our emotions, and then look for a logical justification.

An impairment in the prefrontal cortex causes problems in decision making. People with such damage act impulsively failing to think about consequences. People with prefrontal cortex damage may never learn moral behaviour. Emotions are necessary regarding how we distinguish between good and bad. However, emotions can also interfere with good decisions.

Do people have a limited amount of basic emotions?

Many researchers are hoping to identity a couple of basic emotions. If we are able to identify brain areas that are associated with certain emotions, then we would find strong evidence for certain basic emotions. However, as previously mentioned, no brain areas have been found that are responsible for specific emotions. Why do we then think that there are certain basic emotions? This idea came into mind, because there are specific facial expressions for happiness, sadness, anger, fear, surprise and disgust. Most people in the world can identify pictures of these facial expressions, regardless their culture. However, psychologists don’t see this as enough evidence for basic emotions. They state that the pictures that are used, are selected because of their maximal recognition. They also state that if pictures of spontaneous expressions from the ‘real life’ are used, people would have a harder time to distinguish sadness and disgust and fear and surprise from each other. Observers often see two or more emotions in a face and the emotions that observers see, don’t coincide with the emotions the people of whom the picture was taken of felt. Also, we don’t just use facial expressions to identify emotions. We also look at the body, like gestures and posture. Context and the tone of the voice are also important.

Fight and flight

No single reason for all aggressive behaviours can be identified. Both situational and personal factors are present. An aggressive situation can prime a person to act in an aggressive manner in the future. Priming can be seen in the brain as activity in the corticomedial area of the amygdala.

Environmental factors influence aggression. For example exposure to lead can damage the brain and increase the probability of aggressive behaviours. A mother smoking during pregnancy is known to be connected to aggression. However, mothers who smoke differ from non-smoking mothers in several other ways. Nicotine damages a developing brain. Also heredity plays a role. However, the effects of a specific gene on aggression were shown to produce only weak effects. Instead, the combination of a genetic predisposition and a difficult early environment seems to be more important. A low MAOa (monoamine oxidase A) level together with severe maltreatment during childhood predicts antisocial behaviour.

The aggressive behaviour of males is often dependent on testosterone. Men with more testosterone are also more prone to show aggressive behaviour and more violent crimes. These men show more violent behaviour. Testosterone influences emotional and cognitive responses on angry facial expressions. It reduces the ability to recognize facial expressions consciously, but it enhances the reactions in emotion-related parts of the brain. Among animals, most aggressive behaviours are due to males fighting for partners and females fighting for their offspring.

Aggressive behaviours are linked to low levels of serotonin. In animal studies, social isolation decreased the serotonin turnover (the amount that neurons release and replace, which is estimated from the 5 hydroxyindoleacetic acid (5-HIAA) concentration) in young males. Similar responses might be possible in humans. Animal studies also indicate that low 5-HIAA levels are related to a shortened life span. From the evolution perspective it is problematic questioning how the responsible genes survive: one possibility is that evolution selects for an average amount of aggression and anxiety. On the other hand, aggression can also be a suitable strategy. Several researchers have found a link between low serotonin turnover and violent behaviors or suicide attempts.

A diet affects the serotonin synthesis. Tryptophan is an amino acid which is a precursor of serotonin, and other amino acids can block its transport channels. Tryptophan hydroxylase is an enzyme responsible for converting tryptophan into serotonin. The gene controlling this enzyme differs among people. A less active form is linked to aggressive behaviours. However, the correlation between serotonin and aggression is not straightforward. Instead, high levels of serotonin can inhibit several behaviours.

Fear

A tendency for anxious feelings, avoidance, or approach depends on the situation. Genetic factors also play a role. The nucleus accumbens is an important brain area. The amygdala is a key player in the regulation of anxiety. The startle reflex (the response to loud noise) is used to measure fear or anxiety. The amygdala has cells which respond to rewards, punishments and surprises. The amygdala regulates the hypothalamus which controls autonomic fear responses. It is also connected to the prefrontal cortex, which controls avoidance and approach responses. An impaired amygdala causes problems concerning the learning of fear responses. However, previously learned fear responses function better. The Klüver-Bucy syndrome is a condition which can result following damage in the amygdala. It is characterized by tameness and calmness. Attention to any kind of emotional stimulus raises the amygdala’s responses to the relevant stimulus.

The direction of other people’s expressed emotion is also meaningful. We tend to respond quicker to angry expression when it is directed towards us and to fearful expression when it is directed somewhere else. The amygdala also responds to stimuli which are not recognized consciously. Urbach-Wiethe disease is a rare condition in which the amygdala can be impaired by accumulated calcium. The patients have problems detecting weak emotional signals. People with an impaired amygdala fail to focus on emotional stimuli in a normal manner. The reason why damage to the amygdala impairs recognition of fear is that these people tend to focus on the nose and mouth, not the eyes.

A panic disorder is characterised by periods of fear that arise often and periods of faster breathing, heightened heartbeat, sweating and shivering that arise once in a while. It’s more common in women than in men and also more common in adolescents and young adults than in older people. Some abnormalities in the hypothalamus have been found, but not in the amygdala. A panic disorder is also associated with a decreased activity of GABA and increased levels of orexin (activity).

Drugs used to reduce anxiety alter activity at amygdala synapses. GABA inhibits anxiety responses. Cholecystokinin (CKK) is a neuromodulator which increases anxiety. Benzodiazepines are the most commonly used drugs against anxiety (e.g. diazepam, alprazolam). They bind to GABA-a receptors. Side effects of benzodiazepines are for example sleepiness and memory problems. Endozepines (such as diazepam-binding inhibitor) block the effects of benzodiazepines. They can be seen as anti-benzodiazepines and they are not released by neurons, but by glia. All anxiety-reducing drugs remove anxiety for just a short period of time. One needs therapy to get rid of anxiety for longer periods of time. An unwanted reaction that has been learned (like anxiety) needs to be unlearned as quickly as possible, otherwise there might be a chance of consolidation: the learned effect will become stronger.

Stress

Behavioural medicine stresses people's own decisions (e.g. smoking, exercise etc.) on health. We accept that emotions influence diseases and their recoveries.

Stress is a non-specific response of the body on everything that has been asked from the body. Hans Selye (1979) suggested the general adaptation syndrome, which is a response to stress. The syndrome has the following phases:

1. The alarm stage: activation of the sympathetic nervous system

2. The resistance stage: sympathetic response decreases, cortisol and other hormones are secreted thus maintaining alertness, resisting infections and healing wounds.

3. The exhaustion stage: is a result of prolonged stress. A person is tired, inactive and vulnerable because the body is not able to maintain those heightened responses.

HPA (hypothalamus- pituitary- adrenal cortex as)

Many kinds of events can cause stress, even positive events. Stress-related diseases are common in Western societies, in which we confront several stressful events. Two body systems respond to stress:

  1. The sympathetic nervous system: fight or flight.

  2. The HPA axis, which includes the hypothalamus, pituitary gland and adrenal cortex. The hypothalamus stimulates the pituitary gland to secrete adrenocorticotropic hormone (ACTH), which activates the adrenal cortex to secrete cortisol.

Cortisol increases metabolic activity and is usually considered to be a “stress hormone”. Cortisol improves attention and memory, but prolonged secretion of cortisol can impair the memory and immune systems.

The immune system

The immune system fights against viruses, bacteria and other threats with the help of certain cells. The most important cells are the leukocytes, white blood cells. These are produced in the bone marrow. The system recognises strange material on unknown proteins in the body. These are called the antigens. This will result in the white blood cells attacking the unknown proteins. An autoimmune disease is a condition in which the immune system is too efficient and attacks the body’s own cells.

There are several types of leukocytes (white blood cells):

  • B-cells, which secrete antibodies (proteins that attach to certain antigens). Antigens are proteins on the cell’s surface. The B-cells recognize a body’s own antigens and attacks foreign ones. B-cells ripe in the bone marrow.

  • T-cells attack intruders directly. Some T-cells also help other B-cells and T-cells to multiply. T-cells ripe in the thymus.

  • Natural killer cells attack all intruders. They can fight against tumour cells and cells that are infected with viruses. Unlike the B-cells and T-cells, don’t just work on one type of antigen.

  • B- and T-helper cells help amplifying/multiplying the T-cells and B-cells and they help create the B-memory cells.

  • Macrophages surround the antigen and make it recognizable so it can be destroyed.​

Cytokines are proteins that also fight against intruders and communicate to the brain that the body is sick. Cytokines incite the hypothalamus to create fever, lack of appetite and energy, and sleepiness. The immune system also produces prostaglandins, chemicals that increase sleepiness. Psychoneuroimmunology is a study which focuses on the relationship between the nervous system and immune system.

Effects of stress on the immune system

Stress has many effects on the immune system. It increases its production of natural killer cells and cytokines. Cytokines help to resist intruders, but they also give the same response as though the body were ill. Prolonged stress reactions are harmful for the body. It is suggested that when the energy is used on increased metabolism, there is not enough energy for synthesizing proteins (as the ones of the immune system). Long lasting stress increases the probability of illness. Prolonged stress can also impair the hippocampus.

There are several ways to decrease stress. One of most efficient is social support. Also exercise, breathing routines and meditation can work.

What is the biology of learning and memory? - Chapter 12 (12)

Learning, Memory, and Amnesia

Ivan Pavlov was first to present classical conditioning. Classical conditioning involves presentations of a neutral stimulus along with a stimulus of some significance, the "unconditioned stimulus". Presentation of the significant stimulus evokes an innate response. Pavlov called these the unconditioned stimulus (US) and unconditioned response (UR), respectively. If the neutral stimulus was presented along with the unconditioned stimulus, it would become a conditioned stimulus (CS). If the CS and the US are repeatedly paired, eventually the two stimuli become associated and the organism begins to produce a behavioral response to the CS. Pavlov called this the conditioned response (CR).

Operant conditioning works through reinforcers and punishments. A reinforcer increases the probability of a response in the future, a punishment decreases it.

However, animals have several methods of learning and usually they are difficult to label. The method of learning is also situationally dependent.

Pavlov suggested that learning is based on the growth of connection between two brain areas. Karl S. Lashley proved it does not depend on the connections across the cortex.

Lashley looked for the engram; the physical representation of what has been learned.

Richard F. Thompson presented that lateral interpositus nucleus (LIP), a part of the cerebellum which is important for learning. Lashley tried to find areas in the cortex that could hold the engram, but he couldn’t find this. He therefore concluded that the brain shows mass action and equipotentiality. Mass action means that the cortex works as a whole and the more cortex you have, the better. Equipotentiality means that all parts of the cortex contribute to complex behaviour and every part of the cortex can replace another part. Lashley’s research was limited to only the cerebral cortex. This research also saw all types of memory as physically the same.

Long-term and short-term memory

The memory system can be divided into two categories:

1. Short-term memory is the part of the memory which new information enters first.

2. Long-term memory is a larger storage of memories. If a new information is consolidated in the short-term memory it will enter long-term memory.

Some studies have found proof for a distinction in memory. For instance, the short-term memory and long-term memory differ in capacity. Short-term memories fade away if you don’t repeat them, while long-term memories can be kept for a whole lifetime, even when you haven’t thought about them in a couple of years. Forgetting something that was in short-term memory means you have really forgotten it. When you forget something that was in long-term memory and you get hints, you might remember it again. However, the distinction between these two is not clear. Also the term working memory is presented as an alternative for short-term memory.

Working memory

The working memory only saves information when someone uses this information. this is especially done in the prefrontal cortex. One hypothesis suggests that the working memory can save temporary information by enhanced levels of calcium, which enhances responses later on. Delayed response task is a commonly used procedure to test working memory. In these tests, someone has to react to a stimulus that he/she has heard or seen. Elderly people tend to have problems with working memory, maybe because of changes in the prefrontal cortex.

Amnesia

Amnesia refers to the loss of memory. Anterograde amnesia is an inability to remember events that happened after the brain damage. Retrograde amnesia is an inability to remember events that happened before the brain damage. Most people with amnesia have normal short-term and working memories. The ability to safe long-term information is impaired or even doesn’t take place. The episodic memory also deteriorates. Episodic memories are memories of single events. Imagining future events is to memorize past similar events and to modify them. People who have amnesia therefore cannot imagine future events. Explicit memory consists of the deliberate recall of information. On the contrary, implicit memory refers to the influence of previous experience on behaviour, which a person is not necessarily aware of. Most people with amnesia have better implicit than explicit memory.

Functions of the hippocampus

People with damage to their hippocampus have a diminished declarative memory. Declarative memory is the ability to memorize in words, procedural memory refers to motor skills and habits. People with damage to the hippocampus usually have impaired declarative memory but good procedural memory. The hippocampus seems to be the more important area for declarative memory, as the basal ganglia is more important for procedural memory. Nevertheless, most tasks combine different kinds of memory systems. The hippocampus seems to also be important for spatial memory, and it can even grow after extensive learning experiences. It is suggested that the hippocampus is also related to remembering the details and the context of an event. Thinking of recent memories activates the hippocampus, when it comes to older memories the answer is less straightforward. Memories with strong emotional content are more easily consolidated – this is due to secretion of cortisol.

Other types of amnesia

Korsakoff’s syndrome

Korsakoff’s syndrome is a brain damage characterized by memory loss, confusion and melancholy. It is caused by prolonged thiamine (B1 vitamine) defiance. People with Korsakoff’s syndrome have problems in reasoning their memories. They also tend to confabulate (fill their memory gaps by guessing). Korsakoff’s syndrome can especially be found in heavy alcoholics, because alcoholics often don’t get enough vitamins in their body. The brain needs thiamine to metabolize glucose, which is the brain’s most important fuel. A too low level of vitamin B1 will result in diminishing neurons in the dorsomedial thalamus. This is the most important source of input for the prefrontal cortex.

Alzheimer’s disease

Alzheimer’s disease is another reason for memory loss. People with Alzheimer’s disease have better procedural than declarative memory. Their memory and alertness are different on different days and times. The conclusion that can be drawn is that their neurons don’t function properly. The disease develops gradually, until memory loss, confusion, hallucinations and sleeplessness come into play.

Genes play an especially important part in the early-onset Alzheimer’s disease.

Other than the main areas related to memory processing, almost the entire cortex and several subcortical areas are important for memory. Researchers found that a gene on chromosome 21 is related to early on-set Alzheimer. Genes don’t control the whole disease, but when you understand these genes, you might also understand the underlying causes of the disease. The genes that are responsible for the disease, enable the amyloid beta protein to accumulate in and out of neurons. This protein will come into the brain and damage the functions of glia and neurons. The damaged structures will group together in so-called plaques. The more plaques a person has, the more the cerebral cortex, the hippocampus and other areas will diminish. Alzheimer is also characterised with an abnormal amount of tau protein. Tau produces tangles, which are structures that have been formed from degenerated structures within neural cell bodies.

At this time, there isn’t a cure for Alzheimer’s disease. A commonly used medicine is something that stimulates certain receptors, which enhances excitement. A reason for not having found a cure, is that by the time we have found out that someone has Alzheimer’s disease, it’s already too late to reverse the damage. It’s therefore important to find a way to find out that someone has Alzheimer early on.

Basal ganglia

The episodic memory depends on the hippocampus and it can develop after a single experience. Many semantic memories can also be formed after a single experience. When you hear something interesting, you can remember it for the rest of your life. We need another mechanism to use for probabilistic learning. When you want to predict the weather, you will probably use different information sources. You will probably not be able to explain how you came to your conclusion. Learning things on this way, is dependent on the basal ganglia. Learning things gradually and updating learned things is important for the basal ganglia. People with Parkinson’s disease have a diminished function of the basal ganglia. Their hippocampus enables them to learn easy declarative facts in the beginning, but they are not able to become gradually better in probabilistic tasks. It seems that a distinction can be made between the basal ganglia and other brain areas, when it comes to learning. The following differences can be found in learning between the basal ganglia and the hippocampus:

  • The basal ganglia integrates much information about different situations, while the hippocampus and cerebral cortex can learn something after just one event

  • The basal ganglia needs direct feedback to learn something, the hippocampus and cerebral cortex can also learn from feedback later on

  • The basal ganglia produces habits, while the hippocampus and cerebral cortex produce more flexible responses

  • The basal ganglia mostly produces implicit knowledge, while the hippocampus and cerebral cortex mostly produce explicit knowledge

  • Damage to the basal ganglia results in the loss of well-learned motoric responses and learning habits will also become more difficult. Damage to the hippocampus and cerebral cortex will result in problems in declarative memory (especially the episodic memory).

Storing information in the nervous system

Patterns of electrical activities leave paths on the brain. Pavlov’s studies on classical conditioning were the first ones regarding the physiology of learning. Once the connection between two neurons is made, it is easier to create next time.

The Hebbian synapse refers to a synapse that increases in effectiveness as a result of activity in the presynaptic and postsynaptic neurons.

Adaptation means decreased response to a stimulus when the stimulus is repeated several times. It is not due to muscle fatigue or decreased response of the sensory neuron.

Sensitization means increased response to weak stimulus after exposure to more intense stimulus. Molecular events behind sensitization are serotonin blocking potassium channels of a presynaptic neuron, and continuing the release of transmitter from that neuron. Changes in a synapse can change behavior.

Long-term potentiation (LTP) refers to the strengthening of response in some synapses because of an intense series of stimuli conducted toward a neuron. Some properties make LTP a plausible possibility for the molecular basis of learning and memory: specificity, cooperativity and associativity.

Long-term depression (LTD) is the opposite process to LTP. It occurs at the same time: as one synapse strengthens, another weakens.

Usually LTP depends on changes at glutamate synapses. Two types of glutamate receptors (AMPA and NMDA) are presented.

When glutamate excessively stimulates AMPA receptors, the NMDA are stimulated too. That leads calcium to flow into the cell, which alters a cells future responsiveness to glutamate at AMPA receptors.

Once LTP happens, the AMPA receptors stay tuned. Often LTP is linked to increased release of neurotransmitter from the presynaptic neuron.

LTP does not take place during ‘’traditional” learning, also when exploring new environment, receiving repeated stimulation and creating drug addiction.

Some drugs can enhance learning, such as caffeine as it increases arousal. Ginkgo biloba is a herb which is popular and you can often see it on the television. However, research has found that ginkgo biloba doesn’t really have a big effect. The most way to learn something, is by behaviour. If you want to remember something better, just learn things better, repeat it occasionally and test yourself. Many computer programmes can help with learning things. Physical movement seems to help older people remember things better.

What is the biology of cognitive functions? - Chapter 13 (12)

Lateralization of Function

Many things in nature are symmetrical. The few exceptions are interesting, for example different functions of hemispheres.

Most information is processed in the contralateral hemisphere. However, taste and smell are uncrossed and both hemispheres have control over the trunk and facial muscles.

The corpus callosum is the place where two hemispheres exchange information. Other areas with similar functions are the anterior commissure, the hippocampal commissure and few other commissures.

Lateralization refers to the fact that the hemispheres operate on different tasks.

The left visual field (field that is visible all the time) projects onto the right half of the retina, which sends information to the right hemisphere. The opposite pattern is seen on the right visual field.

The auditory system is a bit different, as each ear sends information to both sides of the brain.

Epilepsy is a condition which manifests itself through excessive synchronized neural activity. The possible causes of epilepsy are brain tumours, toxic substances, gene mutations, brain infections or trauma. In epilepsy the release of the inhibitory neurotransmitter GABA is decreased. Drugs which combat epilepsy enhance GABA.

Severe epilepsy can be treated with surgery, in which the focus is removed. If a person has many foci, surgeons can cut the corpus callosum, the result is epileptic seizures will occur only on the other half of the body and they are less frequent.

The term split-brain people refers to individuals with a cut in the corpus callosum. They can easily use both hands independently, but using them together in unfamiliar tasks causes trouble. The left hemisphere is dominant for speech production for most of the people. When it comes to non-language sounds the hemispheres are equal.

A person in split-brain condition can name objects seen in the right visual field, but not objects seen in the left visual field. Many people with bilateral control of speech tend to stutter – in this sense control of speech happening only on the other side can be beneficial.

When the right hemisphere does something, the left hemisphere doesn’t know why the right hemisphere did this. The left hemisphere thinks that the action was intentional. How will the left hemisphere react? The left hemisphere isn’t surprised and it comes up with an explanation. When the right hemisphere smells something pleasant, the left hemisphere will feel that the mood has changed and think ‘what a delicious meal.’ After having conducted certain experiment, Michael Gazzinga proposed that the left hemisphere could be seen as an interpreter. He thinks that the left hemisphere has the tendency to come up with explanation for certain actions and defend these explanations. This is even the case when the actual causes are unconscious. This is not only the case for split-brain patients, but also for normal people.

When the corpus callosum is cut once, it does not heal. However, the two hemispheres learn how to cooperate using the other connections. The left hemisphere tends to be dominant sometimes and therefore take the control.

The right hemisphere is better at detecting other people’s emotions. Therefore a person with damage in the left hemisphere performs somewhat better in tasks requiring understanding other people’s feelings, as that hemisphere is not disturbing the right one.

An impairment in the right temporal cortex can result in disability to remember the visual features of objects. One hypothesis suggests that the left hemisphere is better at detecting details, as the right hemisphere detects overall patterns.

Anatomical differences between the hemispheres

The differences between the two hemispheres can be seen also in healthy people.

Humans have innate ability to differentiate between sounds. The hemispheres differ slightly from each other from the very beginning, for example the planum temporale (a part of the temporal cortex) is usually larger in the left hemisphere. Also the left hemisphere is specialized in language already. The corpus callosum develops fully between ages 5 and 10. For this reason young children may act in a way which is similar to split-brain people. In the beginning the corpus callosum has more axons than it will have by the end of the maturation process. The reason for this is that two neurons connected by the corpus callosum need to have corresponding functions. Development refers to the selection of certain axons while others are discarded.

Some people are born without the corpus callosum. However, those people differ from split-brain people, as they are able to do many things split-brain people are not. For example, they can verbally describe what they see on either visual field – this is possible because they do not use the right hemisphere for speech. Furthermore, the brain’s other commissures become larger.

For almost all right-handed people the left hemisphere is responsible for speech. Left-handed people show more variation.

Most tasks require the cooperation of both hemispheres.

Evolution and Physiology of Language

Most animals have several ways to communicate: visual, auditory, chemical etc. Human language is unique because of its productivity (ability to produce new signals to present new ideas). It is reasonable to assume that other species also show some rudimentary basis for language. Actually the assumption is right: for example chimpanzees can learn some visual language systems.

Bonobos, one chimpanzee species, resemble humans in many ways. Studies have shown their superior ability to learn language, which might be a result of differences between species, training during sensitive periods, or different training methods.

Also African gray parrots show impressive learning abilities when it comes to language.

Studies among non-human animals can give insight into how to teach a language to someone with learning problems (e.g. autistic children, brain damage patients). They also show an evolutionary basis of language.

Two hypotheses have been presented to explain why people have a better ability to learn language compared to other species:

  • Language was a by-product of overall brain development. This theory has some severe problems. The first being that genes can impair language abilities without impairing intelligence. Another point is a condition called Williams syndrome – a person is mentally retarded but his/her language is fairly fluent.

  • Language evolved as a specialized brain mechanism. Noam Chomsky and Steven Pinker claimed that we have innate mechanism for learning language, called language acquisition device. They suggested that children learn a language so easily that such a mechanism must exist.

Furthermore, Chomsky suggests that children are born with grammatical rules; this is called the poverty of the stimulus argument. Most researchers agree that humans have evolved something that makes them learn language with ease, but the debate about that something continues.

Language learning probably has an early sensitive period, even though there is no sharp cut-off age. When learning a new language, children become familiar with pronunciation and grammar quicker, but adults learn the vocabulary easier.

Language and brain damage

Aphasia refers to language impairment. It is often a result of damage in the Broca’s area, when it is called Broca’s aphasia or non-fluent aphasia.

People with Broca’s aphasia also have trouble in other ways of expressing themselves (writing, gesturing), not just speaking. When they speak they tend to avoid closed class of grammatical form (prepositions, conjunctions etc.) and use only open class terms (nouns and verbs). The problem is with word meanings and not just pronunciation. They do have some knowledge of grammar, even though they do not know how to use it.

Another form of aphasia is Wernicke’s aphasia (also fluent aphasia), which is a result of damage in the left temporal cortex. A person with Wernicke’s aphasia can speak and write fluently but their language comprehension is weak and they have problems remembering the names of objects (anomia). Typical characteristics of Wernicke’s aphasia are (1) articulated speech, (2) trouble finding the right word and (3) a bad language comprehension. Patients have a hard time understanding spoken and written language. They especially have trouble with verbs and nouns.

Music and language have a couple of parallels. Musicians are better at learning a second language. In both music and language the volume and timing of speech are adapted to express emotions. Also, research has shown that languages from the Balkan have less regular rhythms and their music also has irregularly placed tones. Some studies suggest that music and language use the same brain areas. Studies also show that we prefer the music that sounds tone wise like our language. Music can thus be seen as an alternative form of communication.

Dyslexia is a reading impairment, when a person has otherwise proper academic skills and vision. Dyslexic people have some minor brain abnormalities, for example bilaterally symmetrical cerebral cortex.

Reading problems differ from each other. One distinction is made between dysphonetic dyslexics (problems in sounding out words) and dyseidetic dyslexics (failure to recognize the word as a whole).

Many people with dyslexia have auditory problems and trouble detecting the temporal order of sounds, as well as problems with attention.

It might be helpful for a dyslexic person to focus on just one word at a time.

Consciousness and Attention

The mind-body problem asks what the relation is between mind and body. Two ways of thinking exist: the dualism and the monism. Dualists think that mind and body are different substances that exist independently. Monism thinks that the universe consist of one substance.

Consciousness is a difficult concept to define. The operant definition is: If a cooperative person reports the presence of one stimulus and cannot report the presence of a second stimulus, then they are conscious of the first and not of the second.

The definition above cannot be applied for example to animals or infants. Attention is a closely related concept. You can be conscious without paying attention to something, but you can’t pay attention to something if you’re not conscious. A distinction can be made between bottom-up and top-down attentional processes. A bottom-up process depends on the stimulus. When you walk outside and a barking dog runs around the corner, your attention will be drawn to this. Top-down processes are intentional. When you are at a part and looking for your friend in the crowd, you will use top-down processes (looking for a tall, dark person with a blue shirt). Top-down processes depend on the prefrontal cortex and parietal cortex. You can control your own attention, without moving your eyes. The ability to resist distractions fluctuates within a person and between persons. People who often play video games, are better in attention tasks than people who don’t play video games, because the former have better control over their top-down processes.

Inattentional blindness (change blindness) refers to the fact that we are conscious of only the things to which we direct our attention. The consciousness of a stimulus is linked to the amount and spread of brain activity. A conscious stimulus also induces precise synchrony of responses in several areas of the brain.

Binocular rivalry occurs when two different stimuli compete for attention.

According to research, consciousness is an all-or-nothing phenomenon: that is, it has a threshold. A meaningful stimulus captures attention faster than a meaningless stimulus; ergo the brain somehow processes the stimulus before coming conscious of it.

Also later events give meanings to some events, so that we become conscious afterwards.

Spatial neglect is a condition in which a person ignores the left side of the body or the left side of objects. It is caused by damage to the right hemisphere.

In spatial neglect the problem is not impaired sensation, but attention. Only telling a person to focus on the neglected side can increase attention.

Usually people with neglect also have problems in spatial working memory and with shifting attention.

Social neuroscience

Humans have many characteristics that other animals don’t have. One of these characteristics is our social behaviour. Chimpanzees often perform almost as well as humans do on cognitive tasks, but they score much lower on social cognition tests. People can often infer what others are thinking and we try our best to teach others something. This isn’t the case with chimpanzees. Social neuroscience is the study of how chemicals, genes and brain areas contribute to social behaviour. It’s a relatively new research field.

The biology of love

When you’re in love with someone and you look at his/her picture, the brain areas that are involved with rewards will be active. These are the same areas that are active when an addict takes in drugs.

Looking at a picture of your loved one will also activate the hippocampus and other areas that are important for the activation of memories and cognition. This is because you think about all the nice things you have done with your loved one. It seems that love is a combination of motivation, memories, cognitions and emotions.

Women release oxytocin right after and before giving birth. Oxytocin stimulates the breasts to produce milk and encourages the mother to show motherly behaviour. In many animals, oxytocin is responsible for creating a bond between mother and child. Women and men both release oxytocin during sexual activities. That’s why oxytocin is called the love drug. The effects of oxytocin can be studied by giving one half of participants oxytocin and the other half a placebo. Many studies on oxytocin have been conducted and some of the results were that oxytocin makes a man more faithful to his partner, people find their partner more attractive and the trust in the in-group is bigger. However, the effects of oxytocin aren’t always positive. Research has shown that oxytocin turns the attention of people who feel threatened on stress, danger and anger and it also heightens the negative reactions towards others (especially unknown others). One hypothesis is that oxytocin enhances the attention to important social cues. This will result in more attention for facial expressions and positive responses for people we like, but also in more distrust for unknown others or people we doubt.

Empathy and altruism

Some say that civilizations depend on helpfulness. Helpfulness depends on empathy. Empathy is the possibility to identify with others and placing yourself into their shoes. You can feel their pain. Empathy is also common in other animals, but in humans, it is much stronger. The ability to place yourself in another person, depends on the area at which the parietal cortex and temporal cortex come together. There isn’t a single area responsible for empathy and moral behaviour. A couple of areas are together responsible for empathy and moral behaviour.

Your parents have probably told you that you have to be nice to everyone. However, most people will feel empathy for someone they know or who looks like them (relative, good friend). Evolutionary speaking, it’s quite normal to be more altruistic to relatives or someone who looks like you (the chance that someone who looks at you is a relative, is quite big. However, this in-group bias differs between persons. People vary in their degree of empathy and altruism and these variations differ in their brain activity.

Research has found that people who hear a story about the stress of another person and who can place themselves into the person’s shoes, show more activity in the dorsomedial prefrontal cortex and they are also more likely to spend more time and money to help others than people who can’t place themselves in the shoes of the other person. Studies have shown that psychopaths know cognitively that they are hurting or have hurt other people with their actions, but emotionally, their brains show less activity. This means that they can’t empathically identify themselves with others or the pain of others.

How can mental disorders be explained and defined biologically? - Chapter 14 (12)

Addiction and drug use

It seems like addiction is a paradox: you’re doing something that is actually really bad for you. When we talk about addiction, we often talk about alcohol or drugs. However, there are also other forms of addiction, like gambling, gaming and overeating.

Types of mechanisms

A drug that blocks the effects of a neurotransmitter is called an antagonist. A drug that copies the effects of enhances them is called an agonist. A mixed agonist-antagonist is an agonist for one neurotransmitter and an antagonist for the other. Drugs can influence synapses in many ways: they can increase or decrease the synthesis of a neurotransmitter, they can be responsible for the neurotransmitter leaking from the transport bulb or they can work on the postsynaptic receptors. Researchers say that a drug has affinity for a receptor when it attaches to the receptor, like a key into a lock. The efficiency of a drug is the tendency to activate the receptor. Most drugs influence different receptors.

Similarities in drugs

Odds and Milner conducted an experiment with rats in which they put the rats in boxes and in which the rats cut push levers to produce self-stimulation of the brain. Studies found that rats did their best to activate the axons that- directly or indirectly- enhanced the release of dopamine in the nucleus accumbens. Sex, video games, drugs and gambling enhance the release of dopamine. People with depression show the opposite effect: they show a diminished reaction in the nucleus accumbens. According to Berridge and Robinson, dopamine is related to how eager you are to get something and not at how much you like something.

Drug craving

One thing that is common in every addiction is craving. This means that a person is constantly trying to get the product or activity (gaming, gambling). Even after a long period of abstinence, cues that are related to the addiction will create cravings. Someone who has cravings really wants to get the product. It’s not just liking the product, but really wanting and desiring to get the product. Addicted people actual want something they really don’t like (because, who wants to be addicted?). Studies have shown that a repeated exposure to addictive substances diminishes other reward areas. This means that addicted people will have less pleasure in sex and delicious food. An addiction changes the reward system. Repeated exposure to addictive substances also disturbs the prefrontal cortex and other areas that are important for inhibiting impulses.

Tolerance and withdrawal

When an addiction develops further, the effects (especially the fun effects-according to the addict) will become less. This is called tolerance. Because of tolerance, heroin addicts take greater quantities and/or they take heroin more often. Drug tolerance is learned (for a great part). Research with rats has shown that receiving drugs in a certain location will results in more tolerance in that location than in another location. If something is learned, it can also be unlearned. Drug tolerance can be unlearned by extinction. This means that a person doesn’t take the addictive substance for a long period of time.

When the body is accustomed to getting drugs under certain circumstances, it will react strongly when they drug is not present under those circumstances. This is called withdrawal. After stopping using heroin (or other opiates), the withdrawal symptoms will be diarrhoea, vomiting, fear and sweating. Withdrawal symptoms of alcohol abuse are irritation, shaking, sweating, nausea and fatigue. One theory states that addictive behaviour is a way to avoid withdrawal effects. This can’t be completely true, because people who have stopped smoking, report having cravings months or even years after having stopped smoking and cocaine is addictive, but the withdrawal effects are not that severe. Another explanation states that people with an addiction have learned to use the drug (or gamble) to cope with stress.

Predisposition

Most people take things in moderate amounts, while others develop a habit to take many addictive substances. Research with sibling pairs, with one of the siblings having an addiction and the other having no addiction, shows that siblings have the same abnormalities in their brain (in the grey matter, white matter and some brain areas are bigger or smaller than average). It thus seems that some aspects of behaviour and brains are present at the very beginning, regardless of developing an addiction or not.

Genetics

Research with twins and adoptive children has shown that genetics has a strong influence on the sensitivity of alcohol abuse and the abuse of other drugs (especially cocaine). However, it’s quite difficult to find one particular gene that is responsible for this. Many genes seem all to have a small effect on addiction. Few genes are responsible for only addiction. Some genes that contribute to alcoholism, also enhance the chance of a bipolar disorder. Other genes are related to alcoholism, cocaine use, obesity and ADHD.

Environment

Prenatal circumstances contribute to alcoholism. A mother who drinks alcohol during pregnancy, will enhance the chance that her kid will become an alcoholic, regardless of how much she drinks when the child is born and growing up. The circumstances during childhood are also important. People differ in a gene that controls GABA receptors. People with a less sensitive form of these receptors, will have more trouble controlling their impulses. This may lead to the disuse of alcohol. However, studies have shown that children who grew up with parents who really watched them, didn’t have a real problem with controlling impulses. They were able to control their impulses. The environment of adults is especially important for alcoholism that is developed later in life. Research has shown that there are two types of alcoholism: Type II (or Type B) alcoholism and Type I (or Type A) alcoholism. Type II people have a sudden onset of alcohol addiction and that happens before their 25th year of life. These are especially people who have other alcohol addicts in their family. Type I alcoholism comes gradually and after the 25th year of life. This type often depends on stressful events that happen in life, and it doesn’t depend so much on genes. Type I is less severe and is better treatable than Type II.

Research has shown that children who were seen as impulsive, easily bored, outgoing, risk taking and sensation seeking, have a higher chance to develop alcohol abuse. Other studies have shown that sons of alcoholics show less intoxication than average after drinking a moderate amount of alcohol. These sons have 60% chance to develop alcoholism. Research has also shown that alcohol relieves stress for most people, but it relieves stress more for sons of alcoholics.

Treatments

Some people can stop with addictions without help. Others do need help. People can go into therapy or take certain medications. The medicine Antabuse helps against alcoholism, by inducing a feeling of nausea after taking the medicine and alcohol. In that way, alcoholism is associated with diseases. Studies have shown that the use of Antabuse is quite effective. When it works, it complements the commitment of the abuser to quit alcohol. When the alcohol takes a pill every day, he/she will imagine that he/she will get sick after drinking alcohol and this person will not take any alcohol because of this. People who take Antabue and drink, will get nauseous. Sadly, quite a few people stop taking Antabuse instead of quitting alcohol.

It’s often said that people who can’t stop taking opiates, have to take a less severe drug. Methadone looks like heroin and morphine and it activates the same brain receptors and produces the same effects as heroin and morphine. The advantage of methadone is that it can be taken in orally (morphine and heroin can also be taking in orally, but the stomach acids will break these substances down). Methadone enters the blood stream and brains slowly, so the effects will also arise slowly. Methadone will also leave the brain slowly, so the withdrawal symptoms will be less severe. Taking methadone in orally will also diminish the effects of getting infected by a dirty needle. Nowadays, scientist are looking for medicine that can stop cravings. This is still in the experimental phase.

Mood Disorders

In mental disorders both mental basis and experiences are important factors.

Several issues can be triggers for depression: traumatic experiences, genes, hormones, tumors, head injuries etc.

Major depression

Major depression differs from normal sadness in that it is a prolonged condition. The symptoms are suicidal thoughts, concentration problems, lack of energy and pleasure, sleeping problems and feelings of helplessness. It is more a lack of happy feelings than just sadness. Depression is quite a common disorder, as 10% of people have it during the lifespan. It is more common in women than men.

Most depressed people can name the event that triggered the condition. However, depression usually occurs in episodes and later episodes do not necessarily need a trigger. Heritability of depression is moderate. Depression is more probable among people who have a female relative with early-onset depression. Several depression related genes have been found. One such gene controls the serotonin transporter protein, and it has the long type and the short type. These two types occurring together increase the risk of depression. However, these genes are more related to the sensitivity to environmental influences than depression itself.

Some cases of depression are related to viral infections, for example Borna disease seems to cause depression.

Postpartum depression is a form of depression that is launched after giving birth. Usually it goes away with time. The probability of postpartum depression is higher among women who have suffered depression before.

A happy mood is linked to activity on the left prefrontal cortex. Usually people with depression have an active right prefrontal cortex and a less active left prefrontal cortex.

Antidepressant drugs

We can divide antidepressant drugs into four categories:

  1. The tricyclics, which block the transporter proteins that reabsorb serotonin, dopamine, and norepinephrine into the presynaptic neuron. The result is that neurotransmitters continue stimulating the postsynaptic cell. As a side effect the tricyclics also block histamine and acetylcholine receptors causing drowsiness and urinating difficulties among other things.

  2. The selective serotonin reuptake inhibitors (SSRIs), which are like tricyclics but specific to serotonin. Therefore their side effects are milder.

  3. The monoamine oxidase inhibitors (MAOIs) which block monoamine oxidase (MAO). MAO is an enzyme in the presynaptic terminal that metabolizes catecholamines and serotonin into an inactive form. MAOIs are often prescribed after ineffective use of SSRIs and tricyclics.

  4. The atypical antidepressants which are antidepressants that do not fit previous categories, for example an herb called St. John’s wort, which operates like SSRIs.

Most people with depression recover even without treatment. About 30% recover in a few weeks without treatment or with placebo, about 20% respond to either antidepressants or psychotherapy, and a bit over 20% to both of them.

Antidepressants are not very efficient for people with mild depression. Also patients with early childhood trauma (e.g. abuse) respond better to psychotherapy.

There is a debate going on whether antidepressants should be prescribed to children and adolescents or not. Some studies suggest that antidepressants can increase the suicidal risk in children and adolescents.

The way antidepressant drugs work is still partly unclear. Depression is not just a result of neurotransmitter deficit. Antidepressants affect synaptic activity soon after taking them but their behavioural effects come later (after 2 weeks).

Alternative treatments

Electroconvulsive therapy (ECT) is treatment using an electrically induced seizure. Nowadays it is used on patients who do not respond to antidepressants. The most common side effects are memory loss and another depressive relapse. However, ECT is a rather effective and quick method.

Both ECT and antidepressants operates by increasing the proliferation of new neurons in the hippocampus. Another method similar to ECT is repetitive transcranial magnetic stimulation. It is a moderately effective treatment for depression.

Depression affects the sleeping behaviours of a person. Depressed people tend to awaken early and have problems falling asleep again. People who are predisposed to depression have a lifelong trait of altered sleep.

The quickest known method for curing depression is one completely sleepless night. It also increases the proliferation of neurons in the hippocampus.

Regular exercise is also a good treatment for depression, especially when combined with other treatments.

Types of depression

Depression can be divided into two categories:

  1. Unipolar depression, in which a person’s mood varies between normality and depression.

  2. Bipolar depression, in which a person has mood swings between depression and mania.

A person in mania has excessive self-confidence, feelings of excitement and has problems with inhibiting his/her behavior. Bipolar disorder also has a hereditary basis, and two genes have been found to increase the risk. However, we have to note that they do not determine anyone’s bipolar disorder. Antidepressants are not a suitable treatment for people with bipolar disorder. Instead, lithium salts have proved to be effective. Also drugs called valproate and carbamazepine are used.

Excessive glutamate activity can result in mania. All the drugs mentioned above decrease the number of AMPA type glutamate receptors in the hippocampus.

The sleeping patterns of people with bipolar disorder are also altered, as they tend to suffer from sleep deprivation during mania and sleep too much during depression. One possible treatment is to maintain a similar sleeping schedule during different phases.

Seasonal affective disorder (SAD) occurs during a certain season, for example winter time. It is most common near the poles. Usually it is not as severe as major depression. Contrary to other patients with depression, people with SAD have phase-delayed sleep and temperature rhythms.

Schizophrenia

Schizophrenia is characterized by hallucinations, delusions, impairments in thinking and moving, and inappropriate emotional expressions. The symptoms vary between individuals to a great extent.

Schizophrenia can manifest itself either as acute or chronic. Acute schizophrenia has a sudden onset and the probability of recovery is high. In chronic schizophrenia the onset is gradual and the possible recovery takes longer.

The term schizophrenia refers to “split mind”, which denotes the differentiation between the emotional and intellectual side of experience.

Symptoms

The symptoms of schizophrenia fit two categories:

  • Positive symptoms are symptoms that occur even though they should be absent. Positive symptoms are either psychotic (e.g. delusions and hallucinations) or disorganized (e.g. extraordinary behaviors, incoherent speech etc.).

  • Negative symptoms are symptoms that do not occur even though they should, for example impairments in working memory and social interactions.

One of the central symptoms of schizophrenia is disordered thinking, as well as memory impairment. About 1% of people develop schizophrenia during the lifespan. It is most common in the US and Europe, and a bit more common in men than women.

Schizophrenia is related to high dopamine levels in the brain, and men’s brain release more dopamine than women’s, which could be an explanation for the previous fact. Schizophrenia has a genetic basis, at least to some degree, but no certain gene causes it. The closer a relative is with schizophrenia, the greater the risk to develop it. Monozygotic twins show about 50% concordance (agreement).

Studies exploring the genes related to schizophrenia are controversial. One of the genes that seems to be more common among schizophrenics is DISC1 (disrupted in schizophrenia 1).

It is reasonable to assume that any specific gene for schizophrenia would have disappeared during evolution. One hypothesis is that many cases of schizophrenia arise from new mutations. The fact that children with schizophrenia more frequently have older fathers supports this hypothesis.

The neurodevelopmental hypothesis suggests that schizophrenia is related to extraordinary prenatal (before birth) or neonatal (newborn) development of the nervous system. Researchers have found that poor nutrition of the mother, complications at the time of delivery, head injuries and low birth weight have connections to schizophrenia.

Mother’s and child’s inconsistent Rh-factors increase the probability of schizophrenia.

The season-of-birth effect refers to the fact that babies born during wintertime have a slightly higher probability of developing schizophrenia. The cause might be complications of delivery or early nutrition, or viral infections (which are more common in the fall).

Some infections during childhood can also increase the risk of schizophrenia, for example Toxoplasma gondii, a parasite carried by a cat.

Schizophrenia is characterized by some mild brain abnormalities, which are small and vary a lot:

Deficits on the left temporal and frontal areas of the cortex, as well as on most of the cortical areas.

  1. The thalamus is smaller.

  2. The ventricles are larger; the brain cells have less space.

  3. Some areas are slower to mature, for example the dorsolateral prefrontal cortex (impairments in memory and attention).

  4. Cell bodies are smaller, especially in the hippocampus and prefrontal cortex.

  5. Less activity in the left hemisphere.

These changes can be reasons for schizophrenia or as a result of treatment. It is unclear whether brain alterations are progressive (do they increase over time).

Usually schizophrenia is diagnosed after the age of 20. However, most of those people show signs already in childhood, for example memory and attention problems. The late onset can be explained by slowly maturing brain areas.

Treatment

Drugs used to treat schizophrenia are antipsychotic (or neuroleptic) drugs. They are divided into two groups:

  • The phenothiazines, which include chlorpromazine.

  • The butyrophenones, which include haloperidol.

The dopamine hypothesis of schizophrenia claims that the basis of the disorder is a result of the excessive activity at dopamine synapses in specific brain areas. Substance-induced psychotic disorder supports this theory. However, there are some problems with this theory. Antipsychotic drugs block synapses in just a few minutes, but the behavioral alterations take several weeks.

The glutamate hypothesis of schizophrenia claims that the reason is linked to inactive glutamate synapses especially in the prefrontal cortex. Dopamine and glutamate have a connection so that dopamine inhibit glutamate release or glutamate can stimulate neurons inhibiting dopamine release, which would explain abnormal dopamine levels too.

A drug called phencyclidine (PCP) inhibits the NMDA glutamate receptors and is known to produce schizophrenic symptoms in larger doses. Glycine increases the effectiveness of glutamate, and therefore glycine can increase the activity in NMDA.

Drugs used to treat schizophrenia block dopamine synapses in the mesolimbocortical system. As a side effect they also affect mesostriatal system, causing tardive dyskinesia (condition with tremors and involuntary movements).

Second-generation antipsychotic drugs (e.g. amisulpride, risperidone) do not cause these problems, but they have other severe side effects, for example impairment of the immune system.

Autism spectrum disorder

Autism used to be seen as a rare condition, but now the estimates of the incidence of autism vary. Worldwide we think that 1 in 160 people have autism. It is diagnosed more than it used to be. This is partly because we use the label autism more for certain symptoms than other labels, like mental retardation (which is what kids with autism were called back in the day). People are also more aware of the existence of autism. However, it’s also possible that autism is just more common than it used to be.

Symptoms

The autism spectrum disorder contains people that differ in the severity of their difficulties. Therapists used the label Asperger syndrome for people with a mild form a autism. The label autism spectrum disorder is used to indicate autism and what used to be called Asperger syndrome. This summary will use the term autism (for convenience). The autism spectrum disorder is used to indicate different disorders that vary in their severity (relatively mild to really severe). Some people have small autistic behaviours, but these are not enough to get a diagnosis. Autism is more common in boys than in girls. It is common all over the world and researchers haven’t found proof that it’s related to one area, ethnicity or socio-economic status. According to the APA (American Psychiatric Association), these are the most important characteristics of autism:

  • Short-comings in social and emotional exchange

  • Stereotyped behaviour (repeated behaviours)

  • Resistance to a change in routine

  • Shortcomings in gestures, facial expressions and other non-verbal communication

  • Really strong or really weak responses to stimuli (not reaction to pain or screaming severely when they hear a sound)

Many people with autism have also other problems. It is quite common that someone with autism has attentional problems (ADHD). Many people with autism has deficits in their cerebellum. These people are clumsy and show little voluntary eye movements. Parents of children who have autism often see something is wrong with their baby/young child. For instance, the child doesn’t like to be touched. When children with autism are two months, they make as much eye contact as children without autism. However, within two years, their eye contact diminishes. Autism doesn’t only have shortcomings. People with autism are often better in detecting movement in visual stimuli. Some people with autism develop a skill they really excel in.

Genes and other causes

Many genes are linked to autism, but not one of those genes has been found in a high amount in people with autism. It’s probably the case that autism is the result of a mutation or microdeletion. Researches can look at the chromosomes of children with autism and their healthy parents and they can discover which mutations or microdeletions have taken place. Mutations and microdeletions are more common in children with autism than in their brothers or sisters who don’t have autism. Research has shown that most mutations or microdeletions are on a chromosome that is inherited by the father. Older fathers have a higher chance of having a child with autism that younger fathers. Studies have shown that autism is often the results of a mutation in the topoisomerase genes.

Prenatal environmental influences contribute to autism. Some mothers who have autistic children have an antibody that attacks certain brain proteins of their children (12%). Few to no mothers who don’t have children with autism have these antibodies. If we are able to identify these women with those antibodies, we might be able to change certain chemicals on time, so the child doesn’t develop autism. Nutritionists encourage women who are pregnant or who want to become pregnant to take in enough vitamin B9 (folium acid). This can be done by taking in vitamin pills or by enough green vegetables and drinking orange juice. Folium acid is important for the development of the nervous system. Women who take folium acid during pregnancy, have a lower chance of getting a child with autism than other women.

Treatment

There is no medical treatment that helps with the most important problems of bad communicative and social skills. The medicine Risperidone can lessen the stereotyped behaviours of autism, but it also has some side-effects. Behavioural treatments try to diminish the troubles in social and communicative behaviour. This can be done with the help of therapists, parents and teachers. Nowadays, many different treatments are popular, but they don’t really seem to work. Some popular treatments are music therapy, certain diets and therapeutic touch. However, no scientific proof has been found that these methods are effective. Many of these methods give the parents a good feeling about themselves. Parents have the idea they are at least trying to help their child by paying for these treatments.

Biological Psychology - Kalat (12th edition) - Practice questions (EN)

Chapter 1

1. The two kinds of cells in the nervous system are __________, which receive and transmit information to other cells, and __________, which do not transmit information.

A) neurons, glia

B) glia, hypoglia

C) glia, neurons

D) neurons, corpuscles

2. The outer surface of a cell is called the __________ and the fluid inside the cell is the __________.

A) cytoplasm, endoplasm

B) membrane, nuclear fluid

C) wall, goo

D) membrane, cytoplasm

3. Which part of a neuron contains the nucleus?

A) cell body

B) dendrites

C) axon

D) presynaptic ending

4. Neurons have one __________, but can have any number of __________.

A) dendrite, axons

B) axon, dendrites

C) cell body, axons

D) axon hillock, cell bodies

5. As a general rule, axons convey information

A) toward dendrites of their own cell.

B) toward their own cell body.

C) away from the cell body.

D) to glia.

6. An interneuron is

A) a glia cell that separates one neuron from another.

B) a neuron that receives all its information from other neurons and conveys impulses only to other neurons.

C) a neuron that has its cell body in the spinal cord and an axon that extends to a muscle or gland.

D) a cell whose properties are halfway between those of a neuron and those of a glia cell.

7. A neuron that conveys information toward the hippocampus is considered a (an) __________ cell, with regard to the hippocampus.

A) afferent

B) efferent

C) intrinsic

D) motor

8. A neuron that conveys information away from the hippocampus is considered a (an) __________ cell, with regard to the hippocampus.

A) afferent

B) efferent

C) intrinsic

D) sensory

9. In the human brain, glia cells are

A) larger than neurons.

B) capable of transmitting impulses when neurons fail to do so.

C) more numerous than neurons.

D) like neurons, except that they lack axons.

10. One function NOT performed by glia is to

A) remove waste materials.

B) build myelin sheaths.

C) transmit information.

D) guide the growth of axons and dendrites.

11. The difference in voltage between the inside and the outside of a neuron that typically exists is called the

A) concentration gradient.

B) generator potential.

C) resting potential.

D) shock value.

12. What is meant by the term "concentration gradient"?

A) Sodium ions are more concentrated inside the cell and potassium ions are more concentrated outside.

B) Potassium ions are more concentrated inside the cell and sodium ions are more concentrated outside.

C) Sodium ions are more concentrated in the dendrites and potassium ions are more concentrated in the axon.

D) Potassium ions are more concentrated in the dendrites and sodium ions are more concentrated in the axon.

13. The sodiumpotassium pump pumps sodium ions __________ and potassium ions __________.

A) into the cell, into the cell

B) into the cell, out of the cell

C) out of the cell, out of the cell

D) out of the cell, into the cell

14. The sodiumpotassium pump makes possible which of the following features of a neuron?

A) Refractory period.

B) Resting potential.

C) Selective permeability.

D) Saltatory conduction.

15. When the neuron is at rest, which of the following forces tends to move potassium ions OUT OF the cell?

A) Concentration gradient.

B) Electrical gradient.

C) Both concentration gradient and electrical gradient.

D) Sodiumpotassium pump.

16. If a stimulus shifts the potential inside a neuron from the resting potential to a more negative potential, the result is

A) hyperpolarization.

B) depolarization.

C) an action potential.

D) a threshold.

17. If a stimulus shifts the potential inside a neuron from the resting potential to a potential slightly closer to zero, the result is known as

A) hyperpolarization.

B) depolarization.

C) selective permeability.

D) the refractory period.

18. A membrane produces an action potential whenever the potential across it reaches

A) the resting potential.

B) 90 mV.

C) the threshold.

D) the myelin sheath.

19. According to the allornone law,

A) every depolarization produces an action potential.

B) every hyperpolarization produces an action potential.

C) the size of the action potential is independent of the strength of the stimulus that initiated it.

D) every depolarization reaches the threshold, even if it fails to produce an action potential.

20. For a given neuron, the resting potential is 70 mV and the threshold is 55 mV.

Stimulus A depolarizes the membrane to exactly 55 mV.

Stimulus B depolarizes the membrane to 40 mV. What can we expect to happen?

A) Stimulus A will produce an action potential of greater amplitude than stimulus B.

B) Stimulus A will produce an action potential that is conducted at a faster speed than that of stimulus B.

C) Stimulus B will produce an action potential and stimulus A will not.

D) Stimulus A and stimulus B will produce action potentials of the same size.

21. During the entire course of events from the start of an action potential until the membrane returns to its resting potential, the net movement of ions is

A) sodium in, potassium in.

B) sodium out, potassium out.

C) sodium in, potassium out.

D) sodium out, potassium in.

22. The refractory period of a neuron is a period of time when

A) the sodium gates of the membrane are open.

B) the sodiumpotassium pump is active.

C) a usually adequate stimulus cannot produce an action potential.

D) both the sodium gates and the potassium gates are fully closed.

23. Most action potentials begin

A) in the dendrites.

B) in the cell body.

C) at the axon hillock.

D) at the tip of the axon.

24. The velocity of an action potential is

A) the same as the velocity of electricity.

B) approximately the speed of sound.

C) 1100 m/sec.

D) impossible to measure.

25. The function of a myelin sheath is to

A) prevent action potentials from traveling in the wrong direction.

B) increase the velocity of transmission along an axon.

C) increase the magnitude of an action potential.

D) enable an action potential in one cell to influence the transmission in other cells.

26. What are the nodes of Ranvier?

A) Gates in the membrane that admit all ions freely.

B) Branching points in an axon.

C) Places where dendrites join the cell body.

D) Interruptions in the myelin sheath.

Chapter 2

1. The abbreviation EPSP stands for

A) extra psychic sensory perception.

B) exterior partial sensory process.

C) end point stationary physiology.

D) excitatory post synaptic potential.

2. An EPSP is a

A) graded depolarization.

B) depolarization alternating rapidly with a hyperpolarization.

C) graded hyperpolarization.

D) canceling out of competing effects.

3. Spatial summation refers to

A) adding two stimuli from the same source that occurred at different times.

B) the decrease in responsiveness by a neuron that has been stimulated repeatedly.

C) adding two stimuli from different sources at the same time.

D) a progressive increase in the magnitude of action potentials in a given axon over time.

4. An IPSP is a(n)

A) location where a dendrite branches.

B) interruption in a myelin sheath.

C) subthreshold depolarization.

D) temporary hyperpolarization.

5. The synthesis of neurotransmitter molecules takes place

A) in the bloodstream.

B) in the cell body.

C) in the presynaptic terminal.

D) in either the cell body or the presynaptic terminal, depending on the particular neurotransmitter.

6. When an action potential reaches the end of an axon, the depolarization causes what ionic movement?

A) Bicarbonate out of the presynaptic cell.

B) Lithium out of the presynaptic cell.

C) Iron into the cell.

D) Calcium into the cell.

7. The synaptic cleft is

A) the gap between the presynaptic neuron and the postsynaptic neuron.

B) a packet that stores molecules of the synaptic transmitter.

C) a subthreshold depolarization.

D) a dietary precursor to the synthesis of a synaptic transmitter.

Chapter 3

1. The occipital lobe is at the … of the brain

A) anterior

B) superior

C) posterior

2. What isn’t part of the subcortical areas?

A) Hypothalamus

B) Amygdala

C) Hippocampus

3. What is the function of the sympathetic nervous system?

A) It prepares the organs for a resting moment

B) It prepares the organs for activity

C) It prepares the organs for both activity and resting

4. The cerebellum has different functions. Which is not a function of the cerebellum?

A) It plays a role in movement

B) It plays a role in sensory perception

C) It plays a role in balance and coordination

5. The prefrontal cortex:

A) is important for the long-term memory

B) is important for working memory

C) is important for sensory memory

6. How does fMRI work?

A) It measures electrical brain activity by electrodes

B) It shows an image of the brain by measuring blood flow with magnetic fields

C) It measures radioactivity of injected chemicals.

Chapter 4

1. What is the sequence of creating new connections?

A) proliferation- migration- differentiation- synaptogenesis

B) differentiation- migration- proliferation- synaptogenesis

C) migration- proliferation- synaptogenesis- differentiation

2. What happens when an axon no longer receives nerve growth factor (NGF)?

A) The axon won’t be able to grow further

B) The axon will deteriorate and his cell body will die

C) The axon will lose its power in the process of communication

3. When there is a blood clot in the artery, it’s called:

A) Edema

B) bleeding

C) ischemia

4. What is incorrect?

A) On the DNA there are chromosomes

B) The genes are in every cell nucleus of the body

C) There are 23 chromosome pairs

5. What is true about RNA?

A) RNA is like DNA, but exists independently

B) RNA is one string of DNA

C) The function of RNA is to deconstruct unnecessary proteins

6. What isn’t true about evolution?

A) Evolution enhances the genes

B) Evolution means successfully giving the genes to the next generations

C) When a body part is not being used that often, it will be less present in the next generations.

Chapter 5

1. In many ways the eye is analogous to a camera. The light sensitive surface in the back of the eye that would correspond to the film in a camera is the

A) pupil

B) retina

C) blind spot

D) vitreous humor
2. Where are the rods and cones of the eye located?

A) Retina

B) Pupil

C) Optic nerve

D) Cornea
3. The fovea is the part of the retina

A) with the greatest perception of detail

B) that surrounds the point of exit of the optic nerve

C) that falls in the shadow cast by the pupil

D) that has only rods, not cones

4. If you want to see something in fine detail, you should focus the light on which part of your retina?

A) Optic nerve

B) Fovea

C) Part containing mostly rods

D) Cornea

5. Why is the blind spot of the retina blind?

A) It is on the border between the area with rods and the area with cones.

B) It is the point where the optic nerve leaves the retina and there are no rods or cones.

C) It is in the shadow of the pupil.

D) Activity of the receptors is silenced by excessive lateral inhibition.

6. The perception of colour depends on

A) rods

B) cones

C) both rods and cones

D) neither rods nor cones

7. In comparison to the cones, the rods are

A) more concentrated in the fovea.

B) more sensitive to dim light.

C) more important for colour vision.

D) more sensitive to detail.
8. According to the YoungHelmholtz theory, colour vision is based on

A) a different receptor for each colour.

B) three kinds of receptors.

C) a single receptor that produces different responses for each colour.

D) the combined influences of rods and cones.

9. In the most common form of colour blindness people have difficulty distinguishing between what two colours?

A) Blue and yellow

B) Green and blue

C) Red and green

D) Hot pink and neon yellow

10. Males are __________ likely to be colour blind compared to females.

A) less

B) equally

C) more

D) much less

11. Lateral inhibition refers to

A) the effects of autoreceptors on the presynaptic membrane.

B) the reduction of activity in one neuron by activity in a neighbouring neuron.

C) the reduction of activity in one neuron due to inactivity in neighbouring neurons.

D) the opposite effects of the sympathetic and parasympathetic nervous systems.

12. In which layer of the retina is visual information coded in series of action potentials?

A) In the layer of the receptor cells

B) In the layer of the bipolar cells

C) In the layer of the horizontal cells

D) In the layer of the ganglion cells

13. The function of the horizontal cells in the retina is related to:

A) colour vision

B) depth perception

C) perception of brightness

D) increase of contrast

14. Where is the receptive field of a lateral geniculate cell located?

A) In the retina

B) In the midbrain

C) In the thalamus

D) In the cerebral cortex

15. The three types of cells in the primary visual cortex are known as

A) simple, complex, and hypercomplex.

B) W, X, and Y.

C) bipolar, ganglion, and horizontal.

D) inferior, middle, and superior.

Chapter 6

1. According to the law of specific nerve energies,

A) electrical stimulation of the auditory nerve is perceived as sound.

B) a single nerve can convey either auditory or visual information, depending on the frequency of action potentials.

C) the brain has ways of inhibiting the activity of neurons that convey no useful information.

D) if one sensory system becomes inactive, others will compensate by increasing their activity.

2. The intensity of a sound wave is its __________; the perception of that intensity is its __________.

A) frequency, amplitude

B) loudness, tone

C) amplitude, pitch

D) amplitude, loudness

3. Suppose the highest pitch you can hear is about 20,000 Hz. Under what circumstances will that limit decrease?

A) It drops naturally as you grow older.

B) It drops if you go several months without listening to any high pitches.

C) It drops only as a result of injury or disease.

D) It drops if the diet is low in calcium.

4. Three small bones connect the tympanic membrane to the oval window of the inner ear. The function of those bones is to

A) hold the tympanic membrane in place

B) convert air waves into waves of greater pressure

C) spread out the air waves over an area of a larger diameter

D) change the frequency of air waves to a frequency that can be heard

5. The cochlea is part of which sensory system?

A) Visual

B) Auditory

C) Somatosensory

D) Olfactory

6. The receptor cells of the auditory system are known as

A) rods

B) cones

D) hair cells

D) Pacinian corpuscles
7. "Every sound causes one location along the basilar membrane to resonate, and thereby excites neurons in that area" This is one way to state which theory about pitch perception?

A) Volley principle

B) Frequency theory

C) Place theory

D) Opponentprocess theory

8. Damage to the cochlea, hair cells, or auditory nerve can produce

A) conductive deafness

B) nerve deafness

C) temporary deafness

D) hysterical deafness

9. Touch, pain, and other body sensations are known as __________ senses.

A) primitive

B) gustatory

C) olfactory

D) mechanical

10. Which two sensory systems are based on the responses of hair cells?

A) Hearing and vision

B) Hearing and vestibular sensation

C) Olfaction and taste

D) Temperature and pain

Chapter 7

1. Which muscle is "antagonistic" to a flexor muscle in the left leg?

A) A flexor muscle in the right leg.

B) An extensor muscle in the left leg.

C) An extensor muscle in the right leg.

D) Another flexor muscle in the right leg.

2. Which of these disorders is commonly treated with LDOPA?

A) Phenylketonuria (PKU)

B) Parkinson's disease

C) Huntington's disease

D) Schizophrenia
3. Which would be especially important (i.e. used much more than normal) when you run up a flight of stairs at full speed?

A) Fasttwitch muscles

B) Slowtwitch muscles

C) Smooth muscles

D) Intermediate muscles

4. What statement is valid regarding Parkinson's disease?

A) The cerebellum is affected, expressed in a tremor during rest.

B) The basal ganglia are affected, expressed in a tremor during rest.

C) The cerebellum is affected, expressed in an intentiontremor.

D) The basal ganglia are affected, expressed in an intentiontremor.
5. The cerebellum is most important for

A) reflexive movements that use muscles on both sides of the body.

B) slow movements guided by sensory feedback from previous movements.

C) movements that require great physical strength.

D) learned motor programs of ballistic movements.
6. People who have suffered damage to the cerebellum

A) have to plan their movements one at a time, not as a smooth sequence.

B) ignore feedback from previous movements when they are starting a new one.

C) become paralyzed in certain parts of the body.

D) can move normally except that they fatigue quickly.

7. Tests for alcoholic intoxication resemble the tests for damage to the

A) temporal lobe of the cerebral cortex

B) cerebellum

C) spinal cord

D) basal ganglia
8. The caudate nucleus, putamen, globus pallidus, substantia nigra, and subthalamic nucleus make up the

A) basal ganglia

B) limbic system

C) pyramidal system

D) parasympathetic nervous system

9. Following damage to the basal ganglia, people

A) are unable to move.

B) continually move while awake.

C) move inappropriately, failing to respond to instructions.

D) have difficulty initiating movements.

10. A common treatment for Parkinson's disease is a drug that

A) inhibits activity of the immune system.

B) increases the brain's production of dopamine.

C) blocks the enzyme acetylcholinesterase.

D) facilitates the passage of sodium across neuron membranes.

11. Which of the following is NOT common in people with Parkinson's disease?

A) Difficulty initiating voluntary movements.

B) Slowness of movements.

C) Rigidity and tremors.

D) Outbursts of emotional excitement.

12. One of the main symptoms of Parkinson's disease is

A) rapid fatigue of the muscles.

B) loss of saccadic eye movements.

C) difficulty initiating movements.

Chapter 8

1. A "freerunning rhythm" is

A) the activity level of an animal that does not have a biological clock.

B) the sleep pattern of someone who has just finished a period of sleep deprivation and who is now permitted to sleep without restrictions.

C) a pattern of activity that varies unpredictably from one day to the next.

D) the time cycle generated by a biological clock that is not reset.

2. A "Zeitgeber" is

A) a biological clock.

B) an animal that does not have a biological clock.

C) a mechanism that resets a biological clock.

D) a body activity that is controlled by a biological clock.

3. Under what circumstance is a person's circadian activity cycle most likely to drift out of phase with the activity of other people?

A) If the person spends a period of time in the forest, away from clocks.

B) If the person habitually eats a heavy meal just before bedtime.

C) If the person spends a period of time in a cave, away from sunlight.

D) If the person spends a period of time near the equator, where the seasons do not vary.

4. If people live in an environment in which the cycle of light and dark is not 24 hours,

A) within a few days they adjust to waking and sleeping on the new schedule, whatever it is.

B) they adjust better if the cycle is some multiple of 24 (e.g. 48).

C) they adjust better if the cycle is close to 24 (e.g. 25).

D) they fail to adjust at all.

5. What is the role of the suprachiasmatic nucleus in the biological clock?

A) Its neurons generate a 24hour rhythm themselves.

B) Its neurons can reset the biological clock, but they do not generate it.

C) It relays visual information to the biological clock.

D) It relays information from the biological clock to the brain areas that control temperature and activity.

6. A device that can be used to measure stages of sleep is the

A) GSR

B) EEG

C) ACTH

D) FSH
7. Alpha waves occur in an EEG record during

A) nonREM sleep

B) nightmares

C) relaxed wakefulness

D) periods of great excitement

8. REM sleep is synonymous with

A) alpha waves

B) stages 1 and 2

C) stages 3 and 4

D) paradoxical sleep

9. Stages 2, 3, and 4 differ in their

A) percentage of REM sleep.

B) percentage of slow, low amplitude waves.

C) body position.

D) dependence on the synaptic transmitter serotonin.

10. The contradiction in "REM" sleep is the fact that

A) the frequency of the brain waves is low, while the amplitude is high.

B) the brain is very active, while many of the muscles of the body are deeply relaxed.

C) subcortical structures are very active, while the cerebral cortex is inactive.

D) postural muscles are tense, while heart rate and breathing rate are very low.

11. Facial twitches, finger twitches, and eye movements are most characteristic of

A) stage 1 sleep.

B) stage 4 sleep.

C) NREM sleep.

D) REM sleep.

12. Which of the following is NOT associated with REM sleep?

A) Increased probability of dreaming.

B) Difficulty to awaken the person.

C) EEG pattern resembling wakefulness.

D) Postural muscles tense and active.

13. For a normal person, a cycle of sleep from stage 1 to stage 4 and back again to stage 1 lasts about

A) 510 minutes.

B) 90-100 minutes.

C) 4 hours.

D) 78 hours.

14. For a normal person, which part of a night's sleep contains the largest percentage of stage 4 sleep?

A) Early in the night’s sleep.

B) The middle of the night’s sleep.

C) Toward the end of the night.

D) All parts equally.

15. Compared to the early part of a night's sleep, the later part

A) includes a larger percentage of REM sleep.

B) includes a lower percentage of REM sleep.

C) is characterized by declining body temperature.

D) has more rapid cycles through the stages of sleep.

16. What is the relationship between sleep stage and dreaming?

A) Dreams occur only in REM sleep.

B) Dreams occur only in nonREM sleep.

C) Dreams occur in both, but they are more frequent and more vivid in REM sleep.

D) Dreams occur in both, but they are more frequent and more vivid in nonREM sleep.

17. PGO (as in PGO waves) is an abbreviation for

A) paradoxical gradual onset.

B) psychogalvanic oscillation.

C) pons geniculate occipital.

D) Professional Golf Organization.

18. Narcolepsy is characterized by

A) inability to breathe while sleeping.

B) involuntary movements of the limbs while sleeping.

D) sudden periods of sleepiness during the day.

D) sleepwalking.

Chapter 9

1. How do adult mammals with damage to the preoptic area regulate their body temperature?

A) Physiologically.

B) Pharmacologically.

C) Behaviorally.

D) Not at all.

2. If an animal that lacks physiological mechanisms of temperature control gets an infection, it

A) gets cold instead of feverish.

B) gets hot only at the point where the infection began.

C) chooses a hotter environment and gets a fever behaviourally.

D) recovers from the infection faster than animals that do control body temperature.

3. Your posterior pituitary would be most likely to release antidiuretic hormone (ADH)

A) if you are very thirsty.

B) shortly after drinking a large glass of water.

C) if you are very hungry.

D) shortly after eating a large meal.

4. Most of the calories people consume are used

A) to form new memory traces.

B) to propagate action potentials.

C) in exercise.

D) for basal metabolism.

5. The hormone released by the posterior pituitary that causes your kidneys to reabsorb and conserve water is __________.

A) antidiuretic hormone

B) insulin

C) luteinizing hormone

D) oxytocin

6. Osmotic pressure of the body fluids increases when you

A) drink a large glass of water.

B) excrete highly concentrated urine.

C) gain solutes (e.g. sodium chloride).

D) donate blood.

7. When food distends the duodenum, the duodenum releases the hormone

A) CCK.

B) aldosterone.

C) angiotensin II.

D) prolactin.

8. An injection of CCK

A) increases sodium appetite.

B) leads to constriction of the blood vessels.

C) decreases the size of the next meal.

D) causes increased storage of food as fats.

9. When insulin levels are high,

A) fat supplies are converted to glucose, which enters the blood.

B) glucose entry into the cells increases.

C) the individual steadily loses weight.

D) activity and energy levels increase.

10. A homeostatic process is one that

A) is governed by hormones.

B) maintains a variable within a fixed range.

C) depends on a combination of two synaptic transmitters.

D) regulates blood flow.

11. If an animal's body temperature stays the same as that of the environment, it is said to be __________.

A) homeostatic

B) homeothermic

C) poikilothermic

D) hypovolemic

12. One advantage of maintaining a constant body temperature is that it

A) enables the animal to stay equally active at all environmental temperatures.

B) enables the animal to survive on a wider variety of diets.

C) minimizes the energy that must be expended on basal metabolism.

D) enables the animal to detect changes in the temperature of the environment.

13. Which organisms, if any, use behavioural means to regulate their body temperature?

A) Poikilothermic, but not homeothermic.

B) Homeothermic, but not poikilothermic.

C) Both poikilothermic and homeothermic.

D) Neither poikilothermic nor homeothermic.

Chapter 10

1. The … system is the precursor of the fallopian tubes, uterus and vagina and the … system develops into the seminal vesicles.

A) Ovarian; Müllerian

B) Ovarian; Wolfferian

C) Müllerian; Wolfferian

2. What effects of sex hormones produce long-term, structural effects?

A) activating

B) stimulating

C) organising

3. The heightened release of estradiol causes a heightened release of … and a sudden increase in the release of … from the anterior pituitary gland.

A) LH; oxytocin hormone

B) FSH; LH

C) FSH; oxytocin hormone

4. Some people have an anatomy that can be seen as male and female. What is usually the cause of this?

A) androgen insensitivity

B) CAH

C) intersexuality

5. How can having an older brother increase the chances for male homosexuality?

A) The older brother has changed the mother’s immune system in the prenataenvironment.

B) The older brother is also gay.

C) The older brother takes part in the upbringing of the younger brother.

Chapter 11

1. Which of the following would greatly activate the parasympathetic nervous system?

A) A sudden loud noise.

B) Removal of a stimulus that excited the sympathetic nervous system.

C) A controllable or escapable electric shock.

D) A competitive task.

2. One prediction based on the James Lange theory of emotions is that

A) people have to feel an emotion before they can show physiological effects of it.

B) removal of the stimulus for one emotion causes the onset of an opposite emotion.

C) the more intense the physiological arousal, the greater the emotion.

D) all emotional states produce the same physiological arousal.

3. The James Lange theory of emotions and the Cannon Bard theory differ mainly with regard to the question,

A) do emotions depend on autonomic changes or are they independent?

B) do nonhumans experience emotions similar to those of humans?

C) do all emotions give rise to physiological changes, or only certain emotions?

D) which are more intense, the pleasant emotions or the unpleasant ones?

4. The currently accepted view on the role of psychological factors in health is that

A) most causes of disease are best explained in purely physical, not psychological, terms.

B) psychological reactions play a role in both disease and wellness.

C) positive reactions help recovery, but negative reactions do not affect the risk of disease.

D) psychological factors probably are the primary determining factor in almost all diseases.

5. Benzodiazepines are steadily replacing the less desirable barbiturates. Which of the following characteristics of benzodiazepines is TRUE?

A) Benzodiazepines strengthen the working of GABA agonists.

B) Benzodiazepines strengthen the working of GABA antagonists.

C) Benzodiazepines strengthen the working of serotonin agonists.

D) Benzodiazepines strengthen the working of serotonin antagonists.

6. Benzodiazepines are most commonly used in the treatment of __________.

A) psychotic thought disorder

B) anxiety

C) alcoholism

D) stress

7. Which hormone is regulated by the HPA-axis?

A) adrenaline

B) non-adrenaline

C) cortisol

D) dopamine

8. Which system is mostly associated with happiness?

A) BUS

B) BAS

C) BIS

D) BSI

Chapter 12

1. Thiamine deficiency leads to Korsakoff's syndrome because thiamine is necessary for the

A) metabolism of glucose.

B) synthesis of proteins.

C) myelination of axons.

D) protection against toxins.

2. Both classical and operant conditioning can be described as

A) an association between two events.

B) instrumental conditioning.

C) stimulus independent.

D) consequence independent.

3. Pavlov believed that classical conditioning reflected a strengthened connection between a brain area that represents __________ and a brain area that represents __________.

A) reinforcement, punishment

B) a response, a consequence

C) US activity, UR activity

D) CS activity, US activity
4. Which of the following observations (if true) would most seriously CONTRADICT Lashley's principles of mass action and equipotentiality?

A) A learned response is lost after damage to one connection but not others.

B) An individual with damage to the occipital cortex has the same learning impairment as one with damage to the temporal cortex.

C) Within a family of animals, the larger species learn faster and remember longer than the smaller species.

D) Brain damage impairs performance of complex tasks more than simple tasks.

5. Which of the following statements about amnesia is TRUE?

A) Someone who loses memory for past events will also be unable to form new memories.

B) Only damage to the cerebral cortex will produce amnesia.

C) Some people show severe impairments in some aspects of memory without any impairments in other aspects of memory.

D) Amnesia refers to a loss in previously stored memories, not to an impairment in forming new memories.

6. Retrograde amnesia means __________; anterograde amnesia means __________.

A) temporary loss of memory, permanent loss of memory

B) loss of short term memory, loss of long-term memory

C) inability to form new memories, loss of memory for old events

D) loss of memory for old events, inability to form new memories

7. Patients with Korsakoff's syndrome typically suffer from

A) both anterograde and retrograde amnesia.

B) only anterograde amnesia.

C) only retrograde amnesia.

D) neither anterograde nor retrograde amnesia.

Chapter 13

1. Both monkeys and humans with damage to the prefrontal cortex are impaired in their performance of tasks requiring

A) learning of motor skills.

B) discriminating between different visual stimuli.

C) suppressing one's previous response and substituting a new one.

2. What function isn’t asymmetrically laterised?

A) language

B) emotion

C) motoric

3. What term relates to impairment in the Broca area?

A) non-fluent aphasia

B) fluent aphasia

C) anomia

4. When the corpus callosum is cut, a person won’t be able to:

A) point to an object in the right visual field with his right hand

B) draw an object in the left visual field

C) name the object in the left visual field

5. What isn’t true about dyslexia?

A) Children with dyslexia show less arousal when they read something

B) Dyslexia is common in all languages in the same amount

C) Dyslexia is more common in boys than girls

Chapter 14

1. Lithium is most commonly prescribed for

A) seasonal affective disorder.

B) endogenous depression.

C) reactive depression.

D) manic-depressive disorder.

2. Which of the following is NOT a common characteristic of schizophrenia?

A) Deterioration of everyday functioning.

B) Hallucinations or delusions.

C) Impaired understanding of abstract concepts.

D) Alternation between one personality and another.

3. Which of the following is an example of a "negative symptom" of schizophrenia?

A) Hallucinations.

B) Lack of emotional expression.

C) Delusions.

D) Thought disorder.

4. A schizophrenic patient whose main symptoms are lack of emotional expression, lack of social interaction, and lack of speech is said to suffer from

A) positive symptoms.

B) negative symptoms.

C) thought disorder.

D) delusions.

5. Schizophrenia is generally diagnosed for the first time when a person is between the ages

A) 5 and 10.

B) 10 and 15.

C) 15 and 30.

D) 40 and 50.

6. Which of these indications of brain damage is common in people with schizophrenia?

A) Smaller than normal cerebral ventricles.

B) Loss of neurons in the thalamus, cerebral cortex, and hippocampus.

C) Loss of axons between the substantia nigra and the basal ganglia.

D) Heavier forebrains.

7. A restless, impulsive person whose speech rambles from one idea to another may fit which of these categories?

A) Autism.

B) Depression.

C) Mania.

D) Narcolepsy.

8. People with unipolar disorder

A) are always depressed.

B) vary between depression and mania.

C) vary between depression and normal mood.

D) only show chemical imbalances in one half of their brain.

9. Manic-depressive disorder is synonymous with

A) unipolar disorder.

B) bipolar disorder.

C) hypomania.

D) autism.

10. What is the best treatment for seasonal affective disorder?

A) Bright light.

B) Electroconvulsive shock therapy.

C) Adrenal hormones.

D) Dietary changes.

11. What do scientists recommend pregnant women taking, in order to reduce the chance of getting a child with autism?

A) vitamin D (sunlight)

B) fish tablets (omega-3)

C) dopamine

D) folium acid

Answers

Chapter 1

  1. A

  2. D

  3. A

  4. B

  5. C

  6. B

  7. A

  8. B

  9. C

  10. C

  11. C

  12. B

  13. B

  14. B

  15. A

  16. A

  17. B

  18. C

  19. C

  20. D

  21. C

  22. C

  23. C

  24. C

  25. B

  26. D

Chapter 2

  1. D

  2. A

  3. C

  4. D

  5. D

  6. D

  7. A

Chapter 3

  1. C

  2. A

  3. B

  4. B

  5. B

  6. B

Chapter 4

  1. A

  2. B

  3. C

  4. A

  5. B

  6. C

Chapter 5

  1. B

  2. A

  3. A

  4. B

  5. B

  6. B

  7. B

  8. B

  9. C

  10. C

  11. B

  12. D

  13. D

  14. A

  15. A

Chapter 6

  1. A

  2. D

  3. A

  4. B

  5. B

  6. C

  7. C

  8. B

  9. D

  10. B

Chapter 7

  1. B

  2. B

  3. A

  4. B

  5. D

  6. A

  7. B

  8. A

  9. D

  10. B

  11. D

  12. C

Chapter 8

  1. D

  2. C

  3. C

  4. C

  5. A

  6. B

  7. C

  8. D

  9. B

  10. B

  11. D

  12. D

  13. B

  14. A

  15. A

  16. C

  17. C

  18. C

Chapter 9

  1. C

  2. C

  3. A

  4. D

  5. A

  6. D

  7. D

  8. A

  9. D

  10. D

  11. C

  12. C

  13. D

Chapter 10

  1. C

  2. C

  3. B

  4. B

  5. A

Chapter 11

  1. B

  2. C

  3. A

  4. A

  5. B

  6. C

  7. B

  8. B

Chapter 12

  1. A

  2. A

  3. D

  4. A

  5. C

  6. D

  7. A

Chapter 13

  1. C

  2. C

  3. A

  4. C

  5. B

Chapter 14

  1. D

  2. D

  3. B

  4. B

  5. C

  6. B

  7. C

  8. C

  9. B

  10. A

  11. D

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