lecture 9- memory impairments

Question 1

memory and the brain

Answer 1

• Lashley and others had found no evidence for localisation of memory in the brain
• Memory impairments in animals appeared linked to extent of damage (removal of cortex) rather than site of damage
• Key case studies of individuals with memory
  impairments in the 20th Century changed
  understanding of memory and the brain
  fundamentally

Question 2

patient HM

Answer 2

• Henry Molaison (1926 -
  2008)
• Severe epilepsy after
  knocked down by bike at
  age 7
• Surgery by William Scoville
  in 1953 (aged 27)

Question 3

HM: consequences of surgery

Answer 3

• Seizures reduced (but not gone
  completely)
• No personality change
• Preserved intelligence - indeed
  higher than before (IQ 112 vs 104)
• No deficits in perception, abstract
  thinking, reasoning, motivation
• Immediate and profound memory impairments
• Pattern of memory deficits revealed new insights into memory processes and suggested localised memory function in the brain

Question 4

HMs memory impairments

Answer 4

• severe anterograde ammesia
• mild retrograde amesia (for 3 years prior to surgery)
• MLT and especially the hippocampus- key role for laying down new memories?

Question 5

HM’s knowledge of famous
faces

Answer 5

• Sharp decline in ability to
  recognise faces of people
  who became famous after
  his surgery

Question 6

new semantic memories

Answer 6

• Many early studies focussed on HM’s
  failure to lay down new episodic
  memories
• Some early evidence that new
  semantic memories could be formed
• Prompts
• Phonemic (e.g., initial letters)
• Semantic (e.g., what the person did)

Question 7

problems creating new semantic memories as well

Answer 7

-Across word and famous name tests,
new semantic memories severely
impaired
* Also tested famous faces (as in
Marslen-Wilson & Teuber, 1975) but
only looked at semantic cues for recall
* Very little benefit of cuing
* BUT in all experiments performance
for post 1950s stimuli was above
chance
* Some new semantic memory must
be laid down

Question 8

STM vs LTM

Answer 8

• Normal digit span / working memory
• able to retain digit sequences for up to 15 minutes
  if able to rehearse - once stop rehearsal then lost
• could maintain a conversation
• STM does not involve MTL structures?
• Retention much shorter for more complex stimuli like
  faces - difficult to rehearse

Question 9

motor memory

Answer 9

• Able to learn motor skills
• Suggests distinction
  (functional and anatomical)
  between motor learning and
  other memory systems
  Milner (1962)

Question 10

priming

Answer 10

• Show target pattern to join dots and
  ask participant to copy this onto dot
  pattern
• Distractor task
• Then given dots and asked to join
  them in any way they want to
• Look at how frequently they
  produce the target patterns
• Recognition task - copy targets then
  4AFC between patterns to ask
  which they had copied (3 mins)
  earlier

Question 11

priming/perceptual learning

Answer 11

• Gollins incomplete pictures task
• Re-test after 1 hour
• HM didn’t remember having
  done the test before
• But performed better than
  before
• Implicit priming / memory
  without explicit knowledge

Question 12

declarative vs non- declarative memory

Answer 12

• Declarative memory: conscious knowledge of facts
  and events
• Nondeclarative memory: skill learning, motor
  learning, perceptual learning, priming
• develops gradually but with little ability to report
  what is being learned
• Distinct memory systems with distinct anatomical
  localisation

Question 13

what we have learnt from HM

Answer 13

• Memory as a process separate from perception and
  other cognitive processes
• Identified a medial temporal lobe memory system
• Key role in laying down new memories
• Not the site of memory storage
• Not central to accessing stored memories
• Multiple memory systems in the brain

Question 14

HM: a critical look at early findings

Answer 14

• Over-attribution of effects to hippocampus
• Claim not made in early papers
• debate about whether hippocampus or other
  MTL structures are key
• MRI / post-mortem evidence about this…
• Some questions over RA and AA details in later
  studies

Question 15

MRI and post-mortem evidence

Answer 15

• No MRI until 1992 due to
  worries about clips left in
  brain after surgery
• Severe cerebellar atrophy
  (from anti-seizure drugs,
  not operation)
• Shows 5 cm MTL lesion -
  not 8 cm as Scoville
  estimated
• Postmortem confirmed
  this

Question 16

some new semantic learning

Answer 16

• Knowledge of famous names
• First name cue for last name (12 of 35 postop famous)
• Doubled performance when semantic cues provided
  (suggesting semantic knowledge)
• Forced choice recognition of famous names (vs foils) plus
  description of person
• Why different from earlier studies?
• Lots and varied exposure over a long time?
• BUT this is semantic learning in the absence of episodic
  learning - no evidence of new episodic learning in HM
• Separation of semantic and episodic memory formation?

Question 17

re-examining HMs early life memories

Answer 17

• Early reports suggest intact memories for life up to 3
  years pre-surgery
• But autobiographical memory quite impaired when
  examined by Steinvorth et al. (2005)
• Distinction between remote semantic and
  autobiographical memory
• impaired autobiographical
• spared semantic

Question 18

changes in later life for HM

Answer 18

• damage found in 1998 had progressed by 2003
• various white matter lesions found in 2003
• more than typical in healthy ageing
• cortical thinning found in 2003
• changes from 1998-2003 much more extensive than changes from 1992-1998

Question 19

HM

Answer 19

• profoundly life-changing
• unaware of his own age and appearance
  -but not confused when looking in a mirror
• some awareness of his condition
  -* “Right now I’m wondering, have I done or said anything amiss? You
  see, at this moment everything looks clear to me, but what happened just before? That’s what worries me. It’s like waking from a
  dream; I just don’t remember.”
• “Every day is alone in itself, whatever enjoyment I’ve had, and
  whatever sorrow I’ve had.”
• Sense of humour, courteous, high moral standards

Question 20

Wernicke-Korsakoff Syndrome

Answer 20

• Most studied group of amnesic patients (since Korsakoff, 1887)
• Results from chronic alcoholism
• Anterograde amnesia
• Varies between individuals
• Episodic and (some aspects of) semantic memory formation impaired
• Retrograde amnesia
• Temporally graded deficit, particularly bad for episodic retrieval
• Severity of RA and AA not always correlated, suggesting different processes involved
• Spared procedural memory
• Working memory impaired in some but not others
• Seems linked to extent of frontal lobe damage

Question 21

PZ

Answer 21

• Eminent scientist
• Developed WKS at age 65 (chronic alcohol
  abuse) in 1981
• AA and RA
• Wrote autobiography 2 years previously
• graded performance in memory tests
• can rule out lack of encoding of autobiographical information as takem from autobiography (tested on details from autobiography written by PZ)

Question 22

Wernicke-Korsakoff
Syndrome

Answer 22

• Consequence of thiamine
  deficiency
• Extensive damage
• Key damage to mamillary
  bodies, mamillo-thalamic
  tract and dorso-medial
  thalamic nucleus

Question 23

living with severe amnesia

Answer 23

• Profoundly life-changing condition
• Can severely impact an individual’s ability to function
  independently
• Considerable individual differences in deficits and
  consequences
• Two case studies:
• Clive Wearing
• Angie

Question 24

CW (clive wearing)

Answer 24

• b. 1938
• Herpesviral
  encephalitis 1985
• Damage to
  hippocampus, temporal
  lobes, prefrontal cortex
• Severe RA and AA
• Memory restricted to
  about 30 seconds

Question 25

CW

Answer 25

• Preserved IQ
• Normal range on perceptual
  tests
• Fluent reader
• Object recognition difficulties for
  living (bit not non-living) things
• RA - claimed not to have heard
  of almost all tested famous
  people
• Semantic and episodic RA
• diary entries
• refuses to believe previous entries
• can become angry/frustrated

Question 26

a case of successful living with amnesia

Answer 26

• Angie (50 yo at test, IQ 126, Teacher)
• Closed head injury in 1985 (aged 29), resulting in severe AA (also right-sided motor weakness)
• Normal perceptual abilities, executive function
• WM intact, remote semantic memory intact (famous faces etc)
• Autobiographical memory graded (bad for recent, better for remote)
• MRI (1999) showed diffuse white matter lesions, but hippocampus intact
• speculated these disrupt pathways to and from hippocampus (and other MTL structures) so
  speculated hippocampus not working normally
• By 1999 had moved, married, 3 step children, successful career (project manager)
• Good insight into condition, abilities and difficulties
• Strategies to manage home and work tasks - simplifies complex problems into smaller tasks
• Lists to tick off tasks as done (not always needed any more)
• Work - unable to describe nature / detail of work but successful project manager of several projects
  and staff using list strategies