Functional localisation Flashcards
What is localisation of function?
Discipline of neuropsychology interested in mapping specific functions to regions in the brain.
What is visual form agnosia?
perceptual impairment above standard sensory loss, difficulty with discriminating objects
What is associative agnosia?
Perception stripped of meaning - patient could draw a dog, but wouldn’t be able to say what it was.
What is the usual cause of agnosia?
Usually occurs due to a lesion in the occipitotemporal cortex (ventral visual stream)
How does agnosia relate to localisation of function?
Identification of independent processes for visual processing, identification of seperate vental and dorsal visual streams.
Main problems with localisation studies?
Lesion location imprecision, generalisability, task difficulty confound, difficulty of defining function, premorbid abilities.
Are mental processes directly observable?
No - presence must be infered from changed in task performance (Dunn & Kirsner, 2003)
Countering difficulties: Lesion location imprecision
Modern scanning (MRI) has incredibly high spatial resolution. Is expensive and translating results to a standardised model can bring complications.
Countering difficulties: Difficulty in defining function
Current tasks may not be specific enough to target individual processes (e.g. Wisconsin card sorting task). Tasks need to be developed that are better designed to isolate specific processes
Countering difficulties: Premorbid abilities
Use healthy controls, matched for as many factors as possible (aged, education, etc…) - will never be 100% perfect but will offer some valaue in comparrison
Countering difficulties: Task difficulty confounds
Double dissociations - single disscoations influenced by task difficulty confound (Shallice, 1988). Double dissociations may not be strong enough to support the inferences that are usually drawn (Dunn & Kirsner, 2003) but offer more strength to conclusions.
