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Memory _ Amnesia

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					Memory & Amnesia




       Dr. Jenny Wilson
                Memory




   Who would you be without your memories?
   Take a few minutes to write down some ways
    in which you used your memory recently.
Memory processes



 Encoding   Storage   Retrieval
Types of memory
            Rehearsal          Retrieval



  Sensory      Short-term            Long-term


   Loss           Forgetting           Forgetting
Distinctions of memory




 Memory has been described in terms of
divisions, and sub-divisions. (Squire 1987)
Short–term & working memory

                  Our short-term
                   memory can encode
                   information from any
                   modality
                  Working memory can
                   be further divided into
                   memory for
                  Verbal material
                  Visual material
                  Executive tasks
Short-term memory
   Lasts less than 30 secs.
   Maintains post-categorical information.
   Capacity limited – typically, three or four
    items.
   Items can be chunked – e.g. C could be
    one unit, or CAT could be one.
   Loss through decay and interference.
   Maintenance achieved through rehearsal.
           Working memory
            Baddeley & Hitch (1974)

   Proposed that STM is really a working
    memory – tasks involving reasoning are
    affected by concurrent STM retention.
   Two ‘slave’ systems were hypothesized to
    help off-load capacity restrictions from
    the central executive’ – the organising
    principle of STM.
   These two subsystems are referred to the
    phonological loop and visuo-spatial
    sketchpad
Working memory




                 More on this
                  in Lorna’s
                   lecture!
           Long-Term Memory
   Permanent store of
    information.
   The capacity is
    limitless
   Many different kinds
    of memory
   Basic distinction:
   Explicit (declarative)
   Procedural
             Implicit memory:

   Another distinction of LTM is implicit memory
    Schacter (1994)
   Characterised by lack of conscious awareness
    in recollection and during encoding.
   Typical indirect memory tasks include:
   preference judgements, word stem completion,
    lexical and object decision, and word and
    picture naming or categorization (Graf & Masson
    1993 )
   The following memory systems will be ‘explict’
            Episodic memory
   Personal events
    experienced at a specific
    time or place.
   ‘Episodes' that make up a
    life.                          Unlike camera
   E.g.Think of your first day   - reconstructive
    at school, you are bringing
    back to consciousness
    things that have happened
    to you. (autobiographical
    memory)
Semantic memory
            Memory for meaning
            Internal encyclopaedia
            The knowledge you have
             of the world.
            Depending on culture
             similar for all of us.
            E.g. meaning of maiden
             name.

         More on this in Cath’s
               lecture!
Procedural memory
           The part of memory that
            enables you to remember
            how to ride a bicycle or
            play a musical instrument.
           It allows you to retain
            learned physical skills.
           Unlike episodic or
            semantic memories, you
            cannot put a procedural
            memory into words.
Memory as a process
   Some researchers e.g.
    Roediger (1990) argue
    against systems
    approach
   Instead favour memory
    as process view
   See E&K chpt for this
    debate
   Also B&G chpt 8
             EXPERIMENT
   Half the class close eyes or look away
    now.
   Other half read the following passage.
   No peeking!
             Types of Amnesia
   Amnesia is the loss of memory, or memory
    abilities caused by brain damage or disease.
   The pattern of disruptions and preserved
    abilities can tell us about how memory is
    organised.
   Amnesia considered in relation to date of
    brain injury
                trauma


Retro                        Antero


Past                         Present




       Temporal Nature of Amnesia
           Retrograde Amnesia
   Person suffers loss of        Brain of a Korsakoff’s patient.
    memory for events             Damage to medial thalamus &
    BEFORE brain injury.               mammillary nuclei
   E.g. Korsakoff’s (though
    also suffer anterograde)
   Temporal Gradient:
    memory loss greater for
    incidents prior, very early
    LTM may be intact.
   Temporal lobe thought to
    be implicated
Anterograde Amnesia
   Loss of Memory for
    events AFTER the brain       MRI scan of
    insult.                   Alzheimer’s disease.
   E.g. H.M. & Alzheimer’s
   Problem with forming
    new LTM, STM ok.
   Damage to
    diencephalon & medial
    temporal lobe.
    Especially
    Hippocampus (CA1)
What does the amnesic syndrome tell
us about memory?

Recap of first year lecture notes on
  Neuropsychology.
 Isomorphism

 Dissociation

 Double dissociation

 Modularity
        Cognitive Neuropsychology

   Studies cognition in
    Brain-Damaged
    patients
   Provide insight into
    normal cognition
   The role of brain
    structures in different
    processes
Dissociation
   patient performs normally on one
    cognitive task, but is impaired in another
    task

   E.g. patient HM could recall past events
    but can not form new memories
         Double Dissociations

   A finding that some patients do well on task A, but
    poorly on task B, whereas other show the opposite
    pattern.
   So:
   Patient A (with damage in area x of the brain) is
    impaired in task 1 but not task 2 and patient B (with
    damage in area y of the brain) is impaired in task 2
    but not in task 1
          Double Dissociations
   Patients with Damage
    to Broca’s Area can
    Comprehend speech,
    but not Produce speech
   Patients with damage         B   W
    to Wernicke’s area can
    speak fluidly, but can
    not comprehend
    speech
Theoretical Assumptions
                Modularity:
                Cognitive system
                 composed of
                 systems that are
                 independent
                Isomorphism:
                There is a
                 relationship
                 between physical
                 brain and mind
Classic cases in Amnesia
 H.M. (Scoville & Milner
  1957)
Amnesic at age 27
Bi-lateral removal of
  medial temporal lobe
  (2/3 hippocampus)
Mainly anterograde
  amnesia
    What does H.M. tell us about
            memory?
             Intact                      Impaired
   Above average on              Working memory
    WAIS                          Unable to form new
   Remote memory for              long–term memories
    early life (until 10yrs       “every day is alone by
    prior surgery)                 itself, whatever
   Implicit memory                enjoyment I’ve had,
   http://www.nature.com/         whatever sorrow.”
    nrn/journal/v3/n2/slides
    how/nrn726_bx1.html
   Immediate memory
Q. Are memory systems
dissociable?
   H.M. provides striking evidence for the modularity of
    memory.
   Dissociation between STM & LTM (as measured by
    immediate span vs delayed recall tasks)
   Also explicit vs implicit H.M. was able to improve on
    mirror drawing – procedural memory, despite having
    no recollection of performing the task.
Other cases
   H.M.attracted a lot of attention because
    the damage (bi-lateral medial temporal)
    was so extensive & studies so extensive.
   However, medial temporal lobe large area
    – difficult to isolate region of brain
    involved in these different memory
    systems.
   Other cases described with more discrete
    lesions to hippocampal region have since
    been identified.
Cases
   R.B.
   During an open-heart
    operation, suffered an
    ischemia (absence of
    blood flow)
   damage to the pyramidal
    neurons in area CA1 of
    the hippocampus.
   Pronounced anterograde
    amnesia both verbal &
    non-verbal
   Also minor retrograde
    amnesia.
More case studies
   N.A.
   (Squire, Amaral, et
    al, 1989).
   Left dorsomedial
    thalamic nucleus
   The amnesia
    affected verbal
    material with no
    other detectable
    cognitive deficits.
More cases
   PC
   TBI resulting from fall
   CHI from seizure
   Lateral prefrontal &
    lateral temporal region
    of Left hemisphere
   Chronic retrograde
    Amnesia for world
    knowledge
   Intact autobiographical
    memory
Procedural memory
                     Affected by damage to
                      cerebellum; Motor
                      cortex
                     & central grey nuclei
                      e.g. Huntington’s
                      disease.



   Normal brain
      below
Common denominator of
damage?
   Damage to limbic circuits.
   Pathology shared by other cases of amnesia
    including TBI, Alzheimer’s stroke
   Behavioural pathology: defects in remote and
    recent episodic memory but sparing of
    immediate memory.
   So limbic circuits not involved in initial stages
    but mandatory for consolidation of memories.
   LTL involved in semantic memory and accurate
    episodic memory performance. interaction
    between lateral and MTL contributes to
    improved episodic memory retrieval.
Brain regions involved in
memory
              Testing memory

   http://www.sciencemuseum.org.uk/exhibitions/brai
    n/90.asp

				
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