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12) Cognitive Neuropsychology: Detective Work (Example case studies…
12) Cognitive Neuropsychology: Detective Work
Example case studies
Semantic Knowledge Respresentation
Case AC: Knowledge of word meanings
Stroke: various cognitive & linguistic defects (reading, writing, coping pictures, anomic)
Hypothesis 1:
Category-specific loss of semantic information (animals) :red_cross:
Test: Ask same questions about something in-animate: 20 with legs, 10 without
11/20 = no better than chance
Hypothesis 2
: Problem is just with the concept "leg" :red_cross:
Test: Ask does it have a tail
11/20 = no better than chance
Hypothesis 3:
Has lost information about parts of objects :red_cross:
Test: Ask questions not about parts but about overall shape
"Round or not" 15/28
"Coloured or B/W" 12/20
Hypothesis 4
: Has lost information about perceptual properties of objects :check:
Test: Ask about non-perceptual properties of objects
"Is it Australian?" 18/20
"Is it a dangerous animal" 19/20
"Live in water or not" 18/20
Hypothesis 5:
Has lost perpetual knowledge. All perceptual knowledge or just visual? :red_cross:
Test: Ask about perceptual but not visual knowlwedge
Does it make a sound 24/26
Does it have a smell? 19/20
Conclusion
Maybe seperate stores of visual perceptual VS auditory perception (requires another case: double dissociation)
Seperate memory stores of conceptual and perceptual information
Representation of doubled letters in spelling
Evidence from errors
Eg. How could 3 Freddo Frogs be stuck together at a factory
Can reveal information about underlying system used to complete task
Case HE
Single letters have feature markings: HE now loses track of which has the feature making
Specific
Left hemisphere stroke affecting parietal lobe
Consider: how are doubled letter represented?
Subdivisions of visual perception
Case LM
Akinetopsia:
Could see & identify stationary objected but unable to perceive movement (dissociation)
Stroke: bilateral lesions of occipital cortex
Case S
Prosopagnosia:
Perception of non-face objects was normal, unable identify once familiar faces- all looked the sae
Used: movement, clothes, voice to determine
Case OS: Developmental version (less intense)
Case CK
Object agnosia:
Intact facial recognition yet didn't recognise common objects
Saw face in painting but didn't notice it was made of animals unil later
Case JBR: Difficultly naming pictures of only some types of objects (90% inanimate, 6% living things)
Double Dissociation
S = Faces ( :red_cross:) Objects :check:
CK = Faces :check: Objects: :red_cross:
Allows us to now understand Visual perception is split into form perception & movement perception (LM). Within form perception there is faces (S) and objects (CK)
Representation of letter position in reading
Converging evidence
Unimpaired: related phenomenon (eg. reaction time)
Developmental evidence: is it acquired
Related deficits: multiple cases
Case LHD
Borrowed knock-on processing from what they just read
Left hemisphere stroke: temporal & occipital lobes affected
Slot coding not compatible with errors made
The position of letters in reading is not represented acoording to slot coding: converging evidence from studying normal individuals (Cambrdige email)
Approach and methods
Aims
Use models of normal functioning to better understand & explain patterns of cognitive impairment in brain injured patients (MODELS ---> PATIENTS)
Use detailed theories and models of cognitive processes to guide assessment and diagnosis, and also development of evaluation and treatment program (MODELS --> PATIENTS)
USE DATA FROM STUDIES OF PEOPLE WITH IMPAIRMENTS: Test, extend or develop theories about normal cognitive processes (PATIENTS --> MODELS)
Assessment
: What is the cognitive deficit?
Having a theory about the process that we normally accomplish a cognivie task gives ideas about how to assess impairments of the ability to perform this task
Rehabilitation
: What can be done to ameliorate the deficit?
Seek to reinstate the particular component process that have been lost after brain damage
Developmental
Failure to acquire a particular cognitive ability normally
Theories used here: how cognitive abilities are
normally learned
Methods
Any aspect of cognition
: vision, language, audition, attention, memory
Case study:
Intensive scientific study of a single individual with a cognitive deficit
Double dissociation
two complementary
single dissociations across individuals
Strongest form of evidence: show they are seperate
Single dissociation
one
cognitive ability shows impairment while another ability is intact/less impaired
Errors
Accuracy measures preferred
Eg. So many possible types of acquired dyslexia: 2^13 -1 = 4095
Case series:
Multiple case studies, presented and discussed together in one paper
Differing methods from cognitive psychology
Do not combine data across participants
Tend to use accuracy measures rather than reaction time/speed
Focus on single case/small groups
Key assumptions
Properties of modules
Informationally encapsulated:
function is not affected by what is going on in rest of the mind
Domain specific:
can only accept one type of input
Mandatory
: can't be turned on/off
Modularity
: cognitive function involves orchestrated activity of multiple cognitive processes (modules)
Cognitive neuropsychology
Study of cognitive deficits to learn about normal cognition
Types of deficits
Developmental
: failed to develop normally
Acquired
: result of brain injury
Reasons to study cognitive deficits
Understand the
deficit
Theorise effective cognitive-based treatments
Understand
normal
cognition
Understand where cognitive functions are localised in the brain
Summary
Primary method uses case studies
Used evidence from dissociations and errorrs
Strengthened by converging evidence from other subfields of cognitive psychology
Study of deficits to learn about normal cogntiion