Cognitive Neuropsychology and the Discoveries of Broca and Wernicke
Branches of Psychology
Neuropsychology lies within the field of cognitive psychology and focuses on the interrelationship between the physical brain and the cognitive functions of the mind. Cognitive psychology assumes that details of cognitive mechanisms can be inferred through careful use of experimentation with normal human participants. Cognitive neuropsychology believes only when the complete system goes wrong is it possible to grasp the complexity of the mechanisms involved.
The development of neuropsychology can be traced back to the discoveries of Paul Broca and Carl Wernicke in the late 1800's. After an era where attention was being given to phrenology and the study of the skulls contours, they provided vital evidence for the physical connection between specific areas of the human brain and our cognitive functions of speech production and comprehension.
The earliest cognitive neuropsychologists where the phrenologists, who believed our mental abilities were located in different parts of the brain and the contours of the skull revealed the extent of an individuals’ abilities.
Phrenology was based on the idea that mental abilities and functions were located in brain ‘organs’ which had distinct areas on the surface of the brain and could be detected through feeling ‘bumps’ on the outside of the skull. Those 'organs' that were used regularly increased in size and those which were not used decreased in size. According to the phrenologists, this is why the skull changes in contour as an individual develops.
During the phrenology era in the early 1800s, it was not possible to study the brains of the living, only the brains of those who had died could be examined and dissected. Phrenology today has largely been dismissed although its theories and readings are still of great interest to many.
The study of behaviour had yet to be established particularly in those with neurological damage. There was therefore very little information available at the time regarding an individual’s personality and behaviour and how these attributes related to the brain itself.
In the early 20th Century, neurologists were studying brain damaged patients for treatment purposes. Today, cognitive neuropsychologists have a number of goals depending on the type of work they are doing.
Clinical neuropsychologists work with patients who have suffered brain damage and are interested in trying to get a good overall profile of the patients problems and strengths with a view to providing appropriate support.
Research neuropsychologists aim to discover what a patients problems tell us about cognitive functions that have been affected by brain damage and what might be done to aid individual patients.
Broadly, there are four main goals of neuropsychologists:
- lesion localization
- assessment of a patients deficit
- building models of normal cognition
- localization of different cognitive functions within the brain
The Hemispheres of the Human Brain
Such goals illustrate the breadth of neuropsychology but cognitive neuropsychology is part of a much larger field of research; that of neuroscience. This is a multi-disciplinary approach bringing together a number of diverse ways of looking at the brain and cognition including cell anatomy, pathology and neurology. The difference between approaches lies primarily in the level of neural or cognitive functioning being analysed and the research methods employed.
Influential Memory Neuropsychologist, Brenda Milner
Before brain imaging methods were developed, ‘paper and pencil’ techniques were relied upon to build up a picture of the site of brain damage and its effects. The Wisconsin Card Sorting Test (WCST) is one example (Berg, 1948).
A Card Sorting and Feedback Test
The WCST was designed to assess the ability of a patient to change their behaviour as result of receiving external feedback:
- A pack of cards was used that differed in shape, colour and number of objects on each card
- The patient's task was to sort the cards according to the dimensions chosen by the experimenter, but not told to the patient
- The experimenter gives feedback on the sorting by the patient i.e. correct or incorrect
- The experimenter may start by wanting cards sorted by shapes, then after few trials, change and want them sorted by colour
- The idea is that patients, through trial and error, will infer what the examiner is looking for and what the new dimensions are by the feedback in which they receive
Frontal Lobe Brain Damage
It is known that patients with frontal lobe damage have problems with this task. Specifically, they tend to continue to sort cards according to one dimension such as shape despite feedback indicating that dimension is no longer relevant to the rules.
Poor performance such as this on this task was generally taken as an indication of damage to a patients frontal lobes.
Today, Magnetic Resonance Imaging (MRI) can give accurate images of brain damage through the use of non-invasive scanning of patients brains. However, in some cases an MRI scan may show no clear damage despite an obvious display of problems by patients. Standardised tests such as the WCST are therefore still used in some cases.
Read about the remarkable Phineas Gage who in 1848 suffered the most horrific of injuries when an iron rod went through his skill, exiting through his frontal lobes, and he survived. His injuries and the personality changes he experienced as a result changed the path of neuropsychology for ever.
The Discoveries of Broca and Wernicke
Paul Broca is attributed with founding modern neuropsychology. His famous case study, Tan, had suffered a stroke. He found Tan had problems making intelligible words, only being able to produce a few syllables at once, but he could understand fully what was being said to him.
Broca suggested that the part of Tan’s brain that was damaged was the part responsible for coordinating muscle movements needed for speech. Therefore, Tan was experiencing problems with speech production. Post-mortem analysis of Tan’s brain in 1861 confirmed that his brain damage as a result of the stroke was localised to a particular area in the brain, with the rest of his brain remaining intact. This area is now known as Broca’s area.
In 1874, Carl Wernicke worked with patients showing the reverse of Tan’s problems. These patients appeared to be able to speak fluently but had difficulties understanding what was being said to them. Closer inspection found their speech was in fact full of errors and hard to understand.
Wernicke suggested such cases had damage in the brain to the area responsible for storing sound patterns of words, therefore, they were experiencing problems understanding speech. Post-mortem examination of Wernicke’s patients showed a specific area of damage in the temporal lobe and slightly further back than the previously identified Broca’s area.
Although Wernicke’s explanation accounted for poor comprehension, it did not explain why patients experienced speech problems. This is still not fully understood, however this area of the brain is now known as Wernicke’s area due to this early research.
Areas of the brain responsible for speech production and comprehension
Both Broca and Wernicke were ‘localizationalists’ because they believed cognitive functions were firmly located in particular areas of the brain; speech for Broca’s area and comprehension for Wernicke’s area.
Such lesion localization and assessment within the brain were once the most important goals in neuropsychology. However, with the development of cognitive psychology in recent years, these have now changed to create and test models of cognition to help us understand and explain complex cognitive processes, for example reading.
The development of neuroimaging techniques such as Positron Emission Tomography (PET), Magnetic Resonance Imaging (MRI) and Functional Magnetic Resonance Imaging (fMRI) was a significant factor in the evolution of cognitive neuropsychology.
It was no longer necessary to wait until post-mortem to confirm predictions and theories and no need to rely on assumptions. Images can now be obtained of damage in a living brain which has a significant impact on being able to treat patients. Images can also show surgeons exactly where they need to operate and accurate information on which parts of the brain is damaged. This, alongside the early discoveries of Broca and Wernicke has enabled a huge leap forward within neuroscience and cognitive neuropsychology.
- E. A. Berg. (1948). A simple objective technique for measuring flexibility in thinking J. Gen. Psychol. 39: 15-22
- Franz, S.I., (1912) “New Phrenology”, Science, N.S. 35 (896), pp321-32
- Walsh, K. W. (1978). Neuropsychology: A clinical approach. Churchill Livingstone
© 2015 Fiona Guy