lecture 9- memory impairments Flashcards
1
Q
memory and the brain
A
- 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
2
Q
patient HM
A
- Henry Molaison (1926 -
2008) - Severe epilepsy after
knocked down by bike at
age 7 - Surgery by William Scoville
in 1953 (aged 27)
3
Q
HM: consequences of surgery
A
- 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
4
Q
HMs memory impairments
A
- severe anterograde ammesia
- mild retrograde amesia (for 3 years prior to surgery)
- MLT and especially the hippocampus- key role for laying down new memories?
5
Q
HM’s knowledge of famous
faces
A
- Sharp decline in ability to
recognise faces of people
who became famous after
his surgery
6
Q
new semantic memories
A
- 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)
7
Q
problems creating new semantic memories as well
A
-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
8
Q
STM vs LTM
A
- 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
9
Q
motor memory
A
- Able to learn motor skills
- Suggests distinction
(functional and anatomical)
between motor learning and
other memory systems
Milner (1962)
10
Q
priming
A
- 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
11
Q
priming/perceptual learning
A
- 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
12
Q
declarative vs non- declarative memory
A
- 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
13
Q
what we have learnt from HM
A
- 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
14
Q
HM: a critical look at early findings
A
- 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
15
Q
MRI and post-mortem evidence
A
- 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
16
Q
some new semantic learning
A
- 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?
17
Q
re-examining HMs early life memories
A
- 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
18
Q
changes in later life for HM
A
- 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
19
Q
HM
A
- 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
20
Q
Wernicke-Korsakoff Syndrome
A
- 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
21
Q
PZ
A
- 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)
22
Q
Wernicke-Korsakoff
Syndrome
A
- Consequence of thiamine
deficiency - Extensive damage
- Key damage to mamillary
bodies, mamillo-thalamic
tract and dorso-medial
thalamic nucleus
23
Q
living with severe amnesia
A
- 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
24
Q
CW (clive wearing)
A
- b. 1938
- Herpesviral
encephalitis 1985 - Damage to
hippocampus, temporal
lobes, prefrontal cortex - Severe RA and AA
- Memory restricted to
about 30 seconds
25
Q
CW
A
- 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
26
Q
a case of successful living with amnesia
A
- 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
27
Q
A
