To begin with, I will do a couple of articles which will cover the basics of neuropsychology, mainly theory, methodology and overview of key neuropsychological disorders. Later on I will make sure that the page develops and grows further, together with this relatively young discipline.
In the current post I will discuss the main issues and questions posed by neuropsychologists, and will also talk about the methods used in the field, including case (lesion) studies, group (behavioural) studies and different types of brain imaging.
1. Question of functional localisation: can mental functions be dissociated from one another? In other words, is our ability to perform task A related to our ability to perform task B?
2. Question of anatomical localisation: can mental functions be localised in separate brain areas? Is each of the brain areas responsible for a particular function/ability?
3. How do brain functions interact if they do?
4. Plasticity issue: are these functions modifiable and compensatory?
5. Role of genes and environment on anatomy and function of the brain.
These are very broad questions, but essentially they underpin the majority of research in neuropsychology.
Of course, Gall got it really wrong about the lumps. The idea did not live long, and was discredited after the head of a composer Joseph Haydn was stolen after his burial in 1809 by two phrenologists, who wanted to study it and locate the brain areas responsible for musicality. Scandal!
However, in the 1980s Jerry Fodor revived the idea of modularity of mind, leaving out the physical correspondence to mental functions. The important alteration to the previous idea was that the functions were no longer seen as necessarily domain-specific, and mental processes were now understood as interactions between different faculties (or, cognitive modules) such as memory, imagination etc. Thus, Fodor argued in favour of functional localisation rather than anatomical one.
Fodor's theory also included the notion that lesions disrupt specific modules in the brain, and so, the brain with lesion could be described as: normal brain minus the affected region. This idea, however, has been disproven, as several studies showed that the brain is able to compensate for the lost modules, 'moving' lost function to a different brain region.
The theory of modularism proved to be very influential, and has guided the brain studies since 1980s. Now I would like to discuss the methods which neuropsychologists use in order to test the theory and study the modularity of the brain.
Methods of Neuropsychology
Other methods of neuropsychology include brain imaging which can be divided into:
1. Event-related potentials (ERPs)
ERP is a measured brain response to a specific sensory, cognitive or motor stimuli. Its big plus is that it is a non-invasive way of evaluating activity and functioning of the brain. It is also much cheaper than inserting microelectrodes and using fMRI and PET. However, it only produces temporal, but not spacial resolutions. In other words, it can show very precisely when brain activates - however not where it activates.
2. Structural neuroimaging
Structural imaging allows to take a 'picture' of a brain using magnetic fields and radio waves (e.g. MRI, CT). It allows us to see the density of the brain's matter; the denser the area is, the whiter it will appear on the scan. It allows neurologists to see the potential tumours or losses of grey matter.
3. Functional neuroimaging
Functional neuroimaging allows to detect the blood flow to measure neural activity (fMRI, PET). It produces a series of 'colourful' pictures, colours reflecting the changes in blood flow.
There are many other limitations of brain imaging which those studying neuropsychology should be aware of. fMRI measures blood flow, therefore it is an INdirect measurement of neural activity. This is important to remember, as this fact brings out many potential problems:
1. Change in blood flow may demonstrate inhibition as well as activation of the area.
2. There are a lot of individual differences when it comes to brain structure, which can make it hard to interpret functional scans. Here, for example, is a topography of Brodmann area 41 in 9 different subjects; all the scans show quite a different structure and localisation of the area:
4. At the same time, the lack of activation is also ambiguous as it could mean either subliminal (i.e. very weak, undetectable) activation or, indeed, permanent activation, as fMRI only detects changes in blood flow.