12) Cognitive Neuropsychology: Detective Work

Example case studies

Approach and methods

Semantic Knowledge Respresentation

Representation of doubled letters in spelling

Subdivisions of visual perception

Representation of letter position in reading

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

Aims

Methods

Key assumptions

Properties of modules

Modularity: cognitive function involves orchestrated activity of multiple cognitive processes (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

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?

Rehabilitation: What can be done to ameliorate the 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

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

Any aspect of cognition: vision, language, audition, attention, memory

Case study: Intensive scientific study of a single individual with a cognitive deficit

Case series: Multiple case studies, presented and discussed together in one paper

Double dissociation

Single dissociation

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

Errors

one cognitive ability shows impairment while another ability is intact/less impaired

two complementary single dissociations across individuals

Accuracy measures preferred

Eg. So many possible types of acquired dyslexia: 2^13 -1 = 4095

Strongest form of evidence: show they are seperate

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 CK

Case OS: Developmental version (less intense)

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

Double Dissociation

S = Faces ( ❌) Objects ✅

CK = Faces ✅ Objects: ❌

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)

Case JBR: Difficultly naming pictures of only some types of objects (90% inanimate, 6% living things)

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) ❌

Hypothesis 2: Problem is just with the concept "leg" ❌

Hypothesis 3: Has lost information about parts of objects ❌

Hypothesis 4: Has lost information about perceptual properties of objects ✅

Test: Ask same questions about something in-animate: 20 with legs, 10 without

Test: Ask does it have a tail

Test: Ask questions not about parts but about overall shape

Test: Ask about non-perceptual properties of objects

11/20 = no better than chance

"Round or not" 15/28

"Coloured or B/W" 12/20

"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? ❌

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

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

Converging evidence

Specific

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

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

Left hemisphere stroke affecting parietal lobe

Consider: how are doubled letter represented?

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)