Introduction to Issues in Neuropsychology

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Introduction to Issues in Neuropsychology

• Aims and Objectives
• By the end of this lecture you will have learned
• An overview of the course structure, content and
  requirements
• A definition of cognitive neuropsychology
• The main aims of cognitive neuropsychology
• The core assumptions relevant to cognitive
  neuropsychology and their implications
• Required Reading
• Parkin, Ch1 or EY, Ch1.

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Issues in Neuropsychology

• Lecturers Sam Hutton Brendan Weekes
• Contact hours SH - Monday 1030-1200
• Course Text Parkin, A. (1996). An Introduction
  to Cognitive Neuropsychology.
• Course Website
• http//www.biols.susx.ac.uk/ugteach/cws/iin/
• Course structure 3 Lectures a week, 1 Seminar a
  fortnight

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Timetable
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Cognitive Neuropsychology

• What is it?
• Cognitive Psychology - the study of mental
  processes needed for everyday life.
• Based on an analogy between the mind and the
  digital computer - the information processing
  approach Mental Abilities Information
  Processing

Assumptions
The mind is a general purpose symbol-processing
system - symbols are acted on by processes
Cognitive processes take time - RT predictions
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Cognitive Neuropsychology

• What is it?
• Cognitive Psychology - the study of mental
  processes needed for everyday life.
• Based on an analogy between the mind and the
  digital computer - the information processing
  approach Mental Abilities Information
  Processing

Assumptions
The mind is a limited capacity processor
The symbol system and its processes depend on a
neural substrate
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Cognitive Neuropsychology
Neuropsychology - the study of the relationship
between the brain and behaviour
"Neuropsychology is cognitive to the extent that
it purports to clarify the mechanisms of
cognitive functions such as thinking, reading,
writing, speaking, recognising, or remembering,
using evidence from neuropathology" (Campbell,
1987).

• Cognitive Neuropsychology - Can be thought of as
  a specific discipline within cognitive psychology

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Relation to Other Disciplines

• Cognitive science
• develops computational models of cognition often
  to simulate the results from experiments.
• Experimental cognitive psychology
• empirical, behavioural data from controlled
  studies of normal subjects.
• Cognitive neuropsychology
• studies of brain damaged patients.
• Cognitive neuropsychiatry
• studies of patients with psychiatric disorders
• Cognitive neuroscience
• Neural basis of behaviour in animals - often maps
  neural activity to function
• Behavioural Neurology
• Uses data concerning anatomy and physiology of
  CNS to guide interpretations of disordered
  behaviour due to neural damage

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Cognitive Neuropsychology

• "In any well-made machine one is ignorant of the
  working of most of the parts - the better they
  work, the less we are conscious of them.it is
  only a fault which draws attention to the
  existence of a mechanism at all" (Craik, 1943)

Cognitive Neuropsychology has some complex
assumptions in addition to those of cognitive
psychology
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Cognitive Neuropsychology

• What can we conclude about its workings?

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Aims of Cognitive Neuropsychology

• 1. Model confirmation / development
• According to Ellis and Young, cognitive
  neuropsychologists
• explain patterns of impaired and intact
  cognitive performance seen in brain injured
  patients in terms of damage to one or more of the
  components of a theory or model of normal
  cognitive functioning
• draw conclusions about normal, intact cognitive
  processes from the patterns of impaired and
  intact capabilities seen in brain-injured
  patients
• These two approaches are obviously linked, but
  differ in emphasis.

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Aims of Cognitive Neuropsychology

• 2. Cognitive localisation -
• The attempt to specify specific areas of the
  brain as being involved in certain processes
• - some researchers NEVER do this (Ultra or
  Radical CNs)
• - others talk about it but know that it is a
  separate issue from the cognitive theories
  themselves
• - cognitive neuroscientists (e.g. Damasio /
  Goldman-Rakic) are particularly concerned with
  this and use data from patients, NCs, animal
  studies, molecular studies etc..
• Theoretical vs Anatomical paradigms Mackay (2001)

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Cognitive Neuropsychology
Assumptions
Modularity - Mental life is orchestrated by
multiple cognitive processors or modules
Neurological specificity (isomorphism) - there is
a correspondence between the organisation of the
mind and the organisation of the brain (both lead
to locality assumption)
Transparency - observable behaviour will indicate
which module is dysfunctional
Subtractivity - Performance reflects total
cognitive system minus the impaired module(s) -
Plasticity - adaptation???
Universality - There are no individual
differences in the organisation of cognitive
modules
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Assumptions in Cognitive Neuropsychology

• These are the topics of considerable debate
• The debates are very complex! (see extended
  reading list for some examples)
• These asumptions have very important
  implications for the methodologies used in
  cognitive neuropsychology (e.g single case vs
  group studies) and the inferences which cognitive
  neuropsychologists can draw from their data

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Assumption of Modularity
Marr (1982) - Principle of Modular Design - any
large computation should be split up into a
collection of small, nearly independent,
specialized subprocesses

• Fodor (1983) - Modules are
• Domain specific
• Innately specified
• Informationally encapsulated
• Fast
• Hardwired (neurally specific)
• Autonomous
• Not assembled
• Operation is mandatory

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Assumption of Modularity

• Modularity in a strictly Fodorian sense causes
  problems for cognitive neuropsychology-
• Reading is clearly not innate
• Not all cognitive modules appear mandatory
  (e.g.Recognition may be mandatory but is name
  recall?)
• What about top-down processing?
• Fodor also argued that only input (and possibly
  output) processes are modular
• Most cognitive psychologists assume that
  central processes (e.g. reasoning, decision
  making) are also modular to some extent.

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Assumption of Modularity
Neo-Fodorian account of modularity (Coltheart,
1999)
The other Fodorian criteria are not necessary
features of modules.
Whether or not a module possesses any of these
features becomes an interesting empirical question
Assumption of modularity is linked with
assumption of locality (Farah, 1994) and logic of
double dissociation
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Assumption of Isomorphism

• It is possible to have functional modularity but
  not anatomical modularity
• E.g cognitive modules may be distributed across
  wide areas of cortex
• This would imply that any brain damage ought to
  impair a large number of modules
• The fact that so many patients exist with highly
  selective disorders suggest that the assumption
  is tenable.

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Assumptions of Transparency/Subtractivity

• Caramazzas use of the term transparency is
  slightly more specific than most, equivalent to
  the subtractivity assumption as used by Shallice
• The cognitive system of the brain damaged
  subject is the same as that of a normal subject
  apart from a local modification
• E.g brain damage does not result in the de novo
  creation of cognitive modules resulting in a
  cognitive system which is uninterpretable in
  terms of models of normal systems.

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Assumption of Universality

• This assumption is crucial for any group studies
  in cognitive science
• Allows us to consider the average performance of
  a group of individuals to be representative of
  any individual in the population from which the
  group was drawn.