Where does clinical neuropsychology come from?

A clinical neuropsychologist (in health care) focuses on the diagnosis and / or treatment of problems that are related to brain damage. Clinical neuropsychology used to be - and in some countries still is - the field of psychiatrists and neurologists. Over time, clinical neuropsychology has expanded to an independent discipline. More than 2,400 years ago, Hippocrates was convinced that behavior and feeling are the result of brain functioning. Nobody believed him and for centuries the Greeks and Romans believed that the body knew a balance between the elements of water, fire, blood and mucus. A disruption of this balance would lead to illness or abnormal behavior. Only from the 14th century (the Renaissance) did the people start to think critically.

Two notable scientists / philosophers in history:

René Descartes (1596-1650)

Descartes. The soul is an independently functioning intangible unit.

Franz Joseph Gall (1758-1828)

Gall introduced the notion that there are many mental organs in our brains. His views were tested using the clinico-anatomical method: the cognitive loss of function as a result of brain damage (in the language area, for example) was studied in patients, and subsequently the brains of patients were analyzed after their death, after which the location of the lesion was related to the type of functional impairment. Gall formed the very first foundation of clinical neuropsychology as we know it today.

What is cell theory?

The ancient Greeks distinguished between three different forms of soul. According to the ancient Greeks, man was the only one who had all three forms of the soul: a soul to survive, a soul to engage in activities, and a higher-order soul that knows the difference between good and bad. This higher-order soul - the mind - is said to be located in the empty cavities of the brain (the brain ventricles) that were called cells at the time. The first cell (sensus communis) collects all sensory information and forms an image; in the second cell the image (the psychological representation) would be interpreted: what does the image mean? The image is stored in the third cell (memoria). Cell theory has been important for the contemporary cognitive psychology. It is a general system of information processing (our mind can process all types of information) and is the same for everyone. The physiognomy, on the other hand, is about the individual differences in personality or character. Physiognomy means that someone's appearance says something about his or her personality and is attributed to Aristotle.

What did Descartes think?

Descartes renounced all the new insights that developed within the Renaissance and went alone or on what was indisputably true ("I think, so I am."). He stated that people are composed of two substances: the body (res extensa) and the mind (res cogitans), whereby the res cogitans can be seen as a kind of driver. Although the mind would be immaterial, it did place it inside a cavity in the middle of the brain: the epiphysis or the pineal gland.

What did Gall think?

Gall drew up plans for a new psychology, which he called phrenology. He assumed that all psychological functions (including knowledge and affect) are innate. He stated that the mind is not a general information processing system, but that there are specific, separate organs for music, arithmetic and even motherly love. Someone who is better at music has a larger "music organ". The organization is the same for all people (and animals): only the size can vary. His localization was based, among other things, on research into brain damage: for example, he correctly located the language in the front part right behind the eyes. His localization ideas broke with the idea of ​​one soul and Descartes' undivided mind and formed the very first basis of our neuroscience. In addition, Gall argued that the mind is not in the centre of the brain, but on the outside: the cortex. Until then the cortex was only seen as a dried-up crust with no specific function. According to Gall, the brain had independent functions, which at the time was a revolutionary idea.

What is the clinic-anatomical method?

The clinico-anatomical method was used to test Gall's localization ideas by mapping the specific loss of function and later relating them to the site of the lesion. This method was widely used in the 19th century. Paul Broca showed that patient Tan's lesion (this man could only say "tan") was not in the language area as designated by Gall, but more on the side in the left frontal lobe (Broca's area). He noticed that the lesions were almost always in the left hemisphere and he was the first to prove that we use our left hemisphere to speak. This was also the first time that an inequality of the brain halves was demonstrated. His work was universally accepted virtually without challenge. Subsequently the idea arose that the language function could be divided into sub-functions (until now, only speech production had been considered). Carl Wernicke argued that there was a separate center in the temporal lobe for recognizing (only spoken) words. From this dichotomy the distinction arose between Broca's aphasia and Wernicke's aphasia.

What is associationism?

Locke, a huge proponent of empiricism, did not believe in the innate functions as Gall, Broca, and Wernicke claimed. Locke stated that everything is learned: a vision that is also called associationism. John Hughlings-Jackson pointed out to Broca that the location of the lesion can lead to a specific failure, but that it should not be confused with the location of an entire function.

What is holism?

Around 1900 there was much opposition to the localization movement: according to Constantin von Monakow areas of the brain generally worked together. The Gestalt movement (the whole is greater than the parts) increased strongly and Henry Head called localizationists 'diagram makers', putting him in a bad light. Many counterparts of localizationism warned of a great simplification, but they did not have a good alternative: even holists accepted a certain degree of specialization. The Russian Aleksandr Luria offered them the solution in the mid-20th century by coming up with a good balance between localizationism and holism.

What did Luria think?

Luria clinically observed a lot of soldiers who had suffered brain damage during World War II. He was one of the first who focused on the rehabilitation of patients with cognitive disorders and was guided by neuropsychological theory and assessment. He described the brain as a single complex functional system in which multiple subsystems make their own contribution to joint activity. He stated that it is never possible to draw direct conclusions about the responsible subsystems: a holistic view. On the other hand, Luria was a localizationist because he was certain that an accurate analysis can show a specific disruptive factor. With his global model, Luria made a distinction between the following areas:

There are three units that are continually interacting with each other, these are related to the subcortical, posterior and anterior brain areas. The subcortical unit regulates wakefulness and attention; the posterior unit takes on the task of information processing (perception, processing and storage); the anterior unit organizes the behavior (planning, regulation and monitoring).

Within each of these units, a distinction can be made between three hierarchically organized levels of processing: the primary, secondary, and tertiary zones in the brain. The primary areas are the well-known centers for modality-specific sensory information. The secondary zones process the information and give it meaning. In the remaining tertiary zones multimodal integration, the formation of intentions, and the evaluation of one's own behavior takes place.

Although Luria emphasized that for every complex behavior intensive collaboration of both hemispheres is necessary, he denied any involvement of the non-dominant hemisphere in language and speech processes. On the other hand, he regarded the phenomenon of hemispatial neglect as one of the few symptoms exclusive to the right hemisphere.

What is a test battery?

A test battery is often used as a screening tool: cognitive functioning is systematically described in a relatively short time. A specific function is only analyzed in more detail in the event of major deviations. With such instruments, psychologists took over some of the work of the neurologists.

Which two developments contributed to the independence of neuropsychology?

Around 1960 there were two major developments in the United States. This resulted in the emergence of neuropsychology as a separate scientific discipline:

After making acquaintance with Wernicke's work, Norman Geschwind encouraged many to look for specific areas and connections to better map the functioning of the brain. He wrote an influential article about disconnections, the importance of analyzing functions and double dissociations.

Roger Sperry investigated the effects of the split-brain surgery: in patients with severe epilepsy, the fiber tract that connects the two hemispheres (corpus callosum) was cut. This kind of surgery seemed to be a surprising success: epilepsy decreased and functions such as perception, language and memory seemed intact. 

In sum: neuropsychology became an independent discipline (initially in science, but later also in health care) due to the rapid development of research into the different hemispheres and language disorders. Arthur Benton (1909-2006) was one of the fathers of clinical neuropsychology and he wrote many influential articles about patients with aphasia and other types of cognitive impairment.

What are important concepts in cognitive neuropsychology?

(Modules) An example of a module is the language module. We do not have awareness of these processes, and we do not have control over them. We can hardly even influence it. According to Jerry Fodor, a module is domain-specific, innate, encapsulated and has a fixed neural architecture. David Marr also plays a major role in the theory development of cognitive neuropsychology. Marr engaged in the rules (algorithms) that are needed to convert certain information (input) to other information (output). For example, our brain translates sounds into meaning. Marr's approach is based on serial processing: information is converted to the subsequent level of representation. Not much later it became clear that information is not strictly processed serially, but that there is also parallel processing. Influenced by Fodor and Marr, researchers started looking for models of different functions and tried to explain disorders with these models. In particular, much research was done into acquired dyslexia (John Marshall and Cox Coltheart) and agnosia (Elizabeth Warrington): an inability to recognize objects. 

What are neural networks?

Computer programs - called connectionist models - can mimic certain cognitive functions because they work in the same way as the brain: there is a large network of nodes (cells) that are connected to each other (by dendrites). Certain connections are strengthened by learning processes, which can in turn result in a particular response strengthens a response. This is congruent with the association learning of the functioning of memory. There are at least three characteristics of such models that correspond to the functioning of the brain:

• A model is 'economical' because a neural network also learns through trial and error.

• 'Graceful degradation': if certain nodes are damaged, the entire function will not be lost but part of the information will be lost.

• 'Content addressability': a small amount of the information (a few letters) can activate the entire memory trace (the whole word).

Nevertheless, it is clear that the anatomical and physiological properties of the brain differ in several important respects from those of neural networks. The networks offer little insight into how the process actually works. The model is mainly descriptive rather than explanatory. 

What is neuroimaging?

Computed tomography (CT) is an imaging technique that can detect brain injury. ‘Magnetic resonance imaging’ (MRI) significantly increased the possibilities of neuroimaging. With an ‘electro-encephalography’ (EEG) and then mainly with ‘event-related potentials’ (ERPs), more insight was gained into the functional (rather than anatomical) properties of the brain. A consequence of the development of imaging techniques was that more attention was paid to the neural correlates and physiological processes of all kinds of cognitive processes. As a result, less attention has been given to theory development.