COGNITIVE NEUROSCIENCE A virtually completely reductionist scs.ipm.ac.ir/seminars/Workshop/workshop

  • View
    0

  • Download
    0

Embed Size (px)

Text of COGNITIVE NEUROSCIENCE A virtually completely reductionist scs.ipm.ac.ir/seminars/Workshop/workshop

  • • SYSTEMS+ NEUROSCIENCES

    • Empirical methods developed out of standard biomedical sciences over the last 140 years and were in a reasonably modern form by about 1970 (except 4 below)

    • COGNITIVE SCIENCES

    • Empirical methods developed out of conceiving of the ‘human operator’ as a machine, all founded between 1945 and 1970

    Cognitive Neurosciences • NEUROSCIENCES • 1. Effects of lesions in

    animals • 2. Single (multiple-) cell

    recording • 3.Human neuropsychology • 4. Functional Imaging: PET,

    fMRI, EEG, MEG

    • COGNITIVE SCIENCES • 1.Information-processing

    psychology • 2. Neural network modelling

    (connectionism) • 3. Symbolic artificial

    intelligence • 4. Linguistics ((All derived historically from

    the computer revolution of World War II)

    COGNITIVE NEUROSCIENCE • Theoretical questions basically arise from the

    Cognitive sciences but the empirical methods they have available (in human experimental psychology and linguistics) often cannot differentiate between alternative theoretical attempts to answer the Qs. Neither set of methods alone are sufficiently powerful. Hence C.N. imports empirical measures/subjects from the neuroscience disciplines with tasks and models derived from the cognitive science disciplines.

    A virtually completely reductionist approach to cognitive

    neuroscience? • Can it work, say by single-cell recording for a

    series of tasks and modelling of the responses, as post-Dubner & Zeki it could be argued to be the case for a structure like MT/V5 ?

    • The case of the hippocampus • The case of dorsolateral prefrontal cortex

    Hippocampus and its cortical connections

    Approach 1 Hippocampus as the seat of cognitive maps (O’Keefe &

    Nadel 78 for navigation ) • ‘Place cells’- cells which

    respond when the animals enter a particular part of the environment.

    • Can be modelled – predicts changes to responses when environment changed (Burgess & O’Keefe, 1996) with CA3 and CA1 as locus of the place cells); fits head- direction cells in subiculum 4 fields of place cells for an animal in a

    square box

    Hypothetical function derived from single-cell recording

  • Virtual Town Navigation (BurgessN & O’Keefe) Human Hippocampus and Navigation

    • A- Activation produced by controls when navigating in a virtual town

    • B – Volumetric brain Mapping (VBM) (Taxi Drivers vs Controls)

    • C – VBM Correlation with amount of time spent taxi-driving

    A – Maguire et al Science 98; B,C – Maguire et al PNAS 2000

    2.Hippocampus as the seat of episodic memory

    • Tulving’s 72 concept for basis of autobiographical memory characterised in contrast to ‘semantic memory’ (knowledge)

    • First applied to amnesia by Kinsbourne & Wood 75 • Pure amnesia associated with hippocampal lesions

    particularly in patient HM by Milner 1962 (see eg Squire Psych Rev 92; Cipolotti et al Neuropsychologia 01; Spiers et al Neurocase 01)

    Cipolotti et al (Neuropsychologia 2001)

    Selective damage to hippocampus (5SDs below normal)with all other parts of temporal cortex being well within normal limits except for Left parahippocmpal gyrus (2SDs below normal – presumed to arise from loss of white matter fibres from hippocampus – by eye)

    VC (Cipolotti et al 2001)

    • Grossly impaired on many quantitative tests of episodic memory function - both verbal and non- verbal, both recall and recognition

    • For example knowledge of events famous for brief periods of time but then little referred to e.g. incident in British nuclear power facility in 1957 leading to major release of radioactive material

    Treves & Rolls model

    • Detailed specification presented for CA1, CA3, pathway from entorhinal to CA1 which bypasses the dentate gyrus etc

  • Hippocampus • Need to decide which or both of two approaches are

    on the right lines, and if so how they are related • This has not occurred despite 30 years of detailed

    investigation of anatomy and neurophysiology of the hippocampus

    • Assumptions on function permeate all models of the structure. Issue must therefore be addressed on functional level as well as standard neuroscience levels

    Functions of Dorsolateral Prefrontal Cortex

    Paradigms activating Dorsolateral Prefrontal Cortex

    DR = Delayed response; DA = delayed alternation: DMS = Delayed matching to Sample

    Funahashi et al J Neuroscience 1993

    Left sulcus principalis lesions in oculomotor delayed response tasks

    Funahashi et al

    • ‘Disruption of a transient on-line memory process that holds the memory of a given spatial coordinate ‘online’ to direct the response at the end of the delay’

    D’Esposito & Postle 2002

    Dominant perspective – dorsolateral prefrontal cortex is the seat of working memory; Goldman-Rakic identified with the executive component of Baddeley-Hitch information-processing model of working memory

  • Baddeley model inappropriate • Baddeley & Hitch 1974

    produced a model of working memory with one central executive system and two slave systems

    • In Baddeley 1986 identified the ‘central executive’ with Norman & Shallice Supervisory System which is not essentially a storage system

    Rowe et al Science 2000 • This experiment separated maintenance of items

    - exact positions of three dots - from selection. After a variable interval a line appeared on the screen thru’ one of the dots.

    • Ss had to move the cursor to the position of THAT dot.

    • GREEN = maintenance • RED = selection

    Maintenance

    Selection Green – maintenance; Red - selection

  • Baddeley model inappropriate

    • In Baddeley 1986 identified the ‘central executive’ with Norman & Shallice Supervisory System which is not essentially a storage system

    Supervisory System Model • FIGURE 4

    Baddeley(1986) identified ‘executive store’ in his working memory model with the S.A.S component of Norman- Shallice model which is not a store

    Marr’s (1982) tri-level approach • 1. Domain of abstract problem analysis • 2. Computational (software and functional

    architecture) domain • 3. Hard-ware (computer/brain-based)

    • NB ‘Level’ – a misnomer as three domains of questions can be posed at many different grains

    Two dominant functional architectures – brain-derived

    • Modules/ isolable subsystems

    • Computational – need to separate different computations

    • Neuroscientifically plausible because of the anatomical separatons in system level of organisation of the nervous system BUT as part of more complex systems

    • Neural Networks (can be ‘artificial’)

    • Plausible due to local network characterisics of nervous system BUT to be tractable often are grossly simplified and with non- brain based elements: a necessary part of modelling

    • To be discussed in lecture 2

    Neuropsychology & Functional Imaging

    • Three levels of theoretical inferences • 1. From dissociations (N), main activation cross-over activation

    contracts & conjunction analysis (FI) -> functional architecture • 2. Boot-strapping based on plausible inferences from model to

    prediction (examples from N) • 3. From more complex aspects of data (e.g. error patterns (N),

    change in activation correlations over time(FI)) -> more specific aspects of operation of components

    • For N because of the rarity of particular specific lesions one often needs the methodology of single case studies (lectures 1 & 2) – require replication across patients - as well as group studies (lecture 3)

    Single Dissociation :Amnesia

    • Verbal span – can be normal ie 6 or 7 (Drachman & Arbit, 1966)

    Recognition Memory for 50 word lists - grossly impaired (

  • Conceptual framework derives from work on attention – particularly dual tasks. If S devotes more attention to one task devotes less to the other. Each task has its own performance- resource curve

    If curves monotonic upward AND if the same system is the critically involved one THEN iff for two patients A,B :

    Perf (A) > Perf (B) for task I THEN:

    Perf (A) > Perf (B) for task II

    Therefore crossover interaction shows assumption false – 2 systems involved

    Performance – Resource Curves

    Derives from attention literature – Norman & Bobrow 1975

    Amnesics Vs STM patients (initially Warrington & Shallice Brain 1969)

    • Amnesics : Verbal span – can be normal ie 6 or 7 (Drachman & Arbit, 1966)

    Recognition Memory for 50 word lists - grossly impaired (

  • Vallar & Papagno (Brain & Cognition 1986)

    Short-term memory patient PV

    Controls

    STM patient does not show standard recency effect

    Functional specialisation of cortex – eg input phonological buffer

    • Dissociations observed in neuropsychology

    • Local areas of activation from functional imaging

    Shallice & Warrington Quart J Exp Psychology 1972 – Peterson paradigm – with short-term memory patient KF – visual v auditory input Paulesu et al Nat. 1993, 362, 342