Memory

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Memory Amnesia

• Dr. Jenny Wilson

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Memory

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

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Memory processes
Encoding
Storage
Retrieval
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Types of memory
Retrieval
Rehearsal
Sensory
Short-term
Long-term
Loss
Forgetting
Forgetting
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Distinctions of memory
Memory has been described in terms of divisions,
and sub-divisions. (Squire 1987)
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Shortterm 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

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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.

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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

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Working memory
More on this in Lornas lecture!
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Long-Term Memory

• Permanent store of information.
• The capacity is limitless
• Many different kinds of memory
• Basic distinction
• Explicit (declarative)
• Procedural

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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

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Episodic memory

• Personal events experienced at a specific time or
  place.
• Episodes' that make up a life.
• E.g.Think of your first day at school, you are
  bringing back to consciousness things that have
  happened to you. (autobiographical memory)

Unlike camera - reconstructive
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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 Caths lecture!
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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.

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Memory as a process

• Some researchers e.g. Roediger (1990) argue
  against systems approach
• Instead favour memory as process view
• See EK chpt for this debate
• Also BG chpt 8

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EXPERIMENT

• Half the class close eyes or look away now.
• Other half read the following passage.
• No peeking!

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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

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Temporal Nature of Amnesia
trauma
Retro
Antero
Present
Past
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Retrograde Amnesia

• Person suffers loss of memory for events BEFORE
  brain injury.
• E.g. Korsakoffs (though also suffer anterograde)
• Temporal Gradient memory loss greater for
  incidents prior, very early LTM may be intact.
• Temporal lobe thought to be implicated

Brain of a Korsakoffs patient. Damage to medial
thalamus mammillary nuclei
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Anterograde Amnesia

• Loss of Memory for events AFTER the brain insult.
• E.g. H.M. Alzheimers
• Problem with forming new LTM, STM ok.
• Damage to diencephalon medial temporal lobe.
  Especially Hippocampus (CA1)

MRI scan of Alzheimers disease.
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What does the amnesic syndrome tell us about
memory?

• Recap of first year lecture notes on
  Neuropsychology.
• Isomorphism
• Dissociation
• Double dissociation
• Modularity

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Cognitive Neuropsychology

• Studies cognition in Brain-Damaged patients
• Provide insight into normal cognition
• The role of brain structures in different
  processes

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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

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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

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Double Dissociations

• Patients with Damage to Brocas Area can
  Comprehend speech, but not Produce speech
• Patients with damage to Wernickes area can speak
  fluidly, but can not comprehend speech

W
B
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Theoretical Assumptions

• Modularity
• Cognitive system composed of systems that are
  independent
• Isomorphism
• There is a relationship between physical brain
  and mind

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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

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What does H.M. tell us about memory?

• Intact
• Above average on WAIS
• Remote memory for early life (until 10yrs prior
  surgery)
• Implicit memory
• http//www.nature.com/nrn/journal/v3/n2/slideshow/
  nrn726_bx1.html
• Immediate memory

• Impaired
• Working memory
• Unable to form new longterm memories
• every day is alone by itself, whatever enjoyment
  Ive had, whatever sorrow.

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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.

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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.

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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.

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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.

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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

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Procedural memory

• Affected by damage to cerebellum Motor cortex
• central grey nuclei e.g. Huntingtons disease.

Normal brain below
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Common denominator of damage?

• Damage to limbic circuits.
• Pathology shared by other cases of amnesia
  including TBI, Alzheimers 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.

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Brain regions involved in memory
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Testing memory

• http//www.sciencemuseum.org.uk/exhibitions/brain/
  90.asp