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1 Introduction to the module, How cognitive processes work in the normal…
1 Introduction to the module
HISTORY
Ancient Eygypt
Egyptian wrote a hieroglyph of the word 'brain' - first documentation of that word
Neurologists
Broca - suggested the brain is split up into different areas which takes care of particular functions - i.e. specialisation of the brain - assumption was supported with post-mortem examination of Tan's brain, area now known as "broca's area". Wernicke & Lichteim also made suggestions of the structure of the brain.
Behaviourism
If you can't see it, don't study it - brain processes can't be seen. So Broca's suggestion was pushed to the side.
Information processing revolution
Chomsky criticised behaviourism, the advent of computers allowed people to make a new metaphor of how brain processes work (human/computer analogy with the input, hardware, software and output) = led to the information processing approach & the death of behaviourism = led to the birth of cognitive psychology
Neuropsychologists are trying to work out the "software" that allows you to use e.g. memory, visual recognition etc.
Neuroimaging techniques
This also contributed to the death of Behaviourism, bc now you can see the brain whilst a person is alive. Can see the damage of patient's brain's and also see healthy brains.
DEFINITION OF COGNITIVE NEUROPSYCHOLOGY
Overlap between cognitive neuropsych and cognitive neuroscience
These two fields do have an overlap, but they also have unique aspects, so they aren't the same thing.
It is a methodology
Cognitive neuropsychology is a combination of cog psych (studying mental processes) and neuropsych (how brain structure/processes control behaviour) = cognitive neuropsychology, which tends to look at this by looking at brain damaged patients. It's simply a method that helps us understand the cognitive system.
AIMS OF COGNITIVE NEUROPSYCHOLOGY
Lesion Localisation
Try and find where the brain damaged sites are located. This can be done by giving patients cognitive tests. Can also be done using neuroimaging (CAT scan, MRI, PET scan, fMRI etc) - all have its own special abilities for looking at different aspects of neural firing
EVAL
However, neuroimaging might suggest that there's no damage but acc cognitive testing might show you there's a lot of damage/impaired abilities. Additionally, some neurimaging techniques like TMS can only be used for cortical areas, so can't be used for things like looking at memory.
Assessment of deficit
This is a clinical neuropsychologists job - trying to understand the patient's problems and deficits, which is very important for rehabilitation, so the intact abilities can be used to help them cope.
Model building
This is the cognitive neuropsychologists job, where data from BD patients can be used to infer about the normal healthy participants mental processes. This patient data can either be confirmatory or help develop new models.
Localisation of function
So this is where you want to understand what brain areas are involved in certain processes. Some researchers don't agree with this or care about this - But acc this is about how what brain area's do, how they communicate with each other, and what damage in these brain areas affect these abilities.
PRINCIPLES OF NEUROPSYCHOLOGY
Why look at brain damaged patients
Only when something goes wrong can you understand how complex it is (how complex mental processes are e.g. memory is very complex bc it isn't a unitary thing), by learning about the ability that has gone wrong - gearbox in the car, the fanbelt etc.
Subtractivity
You assume that the patients brain before damage was intact and normal (i.e. there wasn't any underlying abnormalities that make the brain different to healthy participants brain). You are studying the missing piece of the jigsaw (i.e. the brain damage) by looking at what abilities the patient can't do, bc then that means that all these lost abilities is what the missing piece of the jigsaw controlled. After seeing several patients who all have a different piece of the jigsaw missing, you'll then understand the whole system.
So you need the brain to be intact before the brain damage, and need to be sure that no plasticity has occured.
Associations
Researchers identify that there are separate functions in the brain by looking at what symptoms co-occur - this can be grouped together as a syndrome. E.g. Wernicke-Korsakoff Syndrome.
It would be premature to think that the two symptoms are controlled by the same brain area - separate functions just controlled by brain area's that are very close to one another.
Dissociations
When one function happens without the other function - can support earlier models e.g. modal model of memory & patient HM patient KF.
When you get dissociations, you need to follow the law of parsimony & try and explain it through the easy explanation first, and if that doesn't work (if other patient data comes about which doesn't fit into this easy explanation) only then can you go onto more complex explanations.
Double dissociations
HM's data alone can't support multi-store model (law of parsimony - the hypothetical explanation of how memory depends on effort), but along with KF's data, this doesn't fit the hypothetical explanation, hence that means memory is a multi-layered function bc we have this double dissociation & the multi-store model can be supported.
When function A can occur without function B, and function B can also occur without function A - this would show that these functions are separate abilities controlled by different brain areas.
EVAL
- KF's evidence can also be used to weaken the multi-store model, bc the model suggests that info has to go through STM to get to LTM, but KF (who has bad STM but good LTM) shows that this isn't necessarily true and hence can be used to weaken the multi-store model.
1 Caveats of Cognitive Neuropsychology
The alien within us
Unusual cognitive system
For the principle of subtractivity to work, you need to make sure that the patient's cognitive system was effectively the same as any other participants BEFORE their brain damage.
The principle is not met if the patient had an unusual cognitive system even before brain damage e.g. underlying abnormalities such as epilepsy or they have compensatory strategies. This means the patient's data cannot be used to generalise as they're not representative of the normal population.
Comparing two brains
Identical vs. non-identical
Non-identical twins didn't have the same brain (obv). Even identical brains were found to not be 100% similar - the spare of the individual gyri differed slightly between identical twins. Thus the brains between two strangers can't be the same!
Types of Lesions
The brain damage between different patients will never be the same, even lesions caused by surgery can't ever be the same because neurosurgeons can't make clean lesions. Thus, the patient can have lots of other unrelated or related deficits. So comparing two patients can be complex and difficult - researchers need to take into account all the damage suffered by a patient & not zoom into the areas they're interested in.
Scientific research moves forward by replication and extension of studies, but how can replication occur because two patients brain (size and extent of brain lesion) is never going to be the same.So can't make generalisations, bc even small differences in lesion size can have major impact on performance.
Plasticity
Subtractivity principle only works if there's no plasticity, which is where the brain repairs itself. Patients who have had plasticity in the brain can't be used to infer about the regular brain system.
Research decisions
Single vs group study
Whether to analyse single vs. group = look at tutorial
Acquired Vs. developmental disorders.
Researchers study acquired patients more in order to ensure principle of subtractivity is applied (so the brain was normal before brain damage). Also with developmentals, plasticity could have occurred since plasticity can occur in a child's brain
Acquired
= when you were healthy, then got brain damage, and that led to you losing some abilities.
Developmental
= you were born with deficits, possibly due to a genetic inheritance.
How cognitive processes work in the normal human brain...?