Transcript c83lnp: Neuropsychology - University of South Carolina

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Memory
• Chris Rorden
• Anterograde Amnesia
• Short vs Long Term Memory
• Episodic vs Procedural Memory
• Confabulation
www.mricro.com
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HM
 Severe epilepsy, treated with surgery to bilaterally remove
medial temporal lobes.
 Operation 9/1953, 27 years old
 Tested 4/1955, age 29
– Reported date as 3/1953, age of 27
– No memories since operation
– IQ better than pre-op (112)
– Fewer seizures
 Profound failure to create new memories
– Can’t find new home (after 10 mos.)
– Can’t remember new people, names, tasks
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HM
 Deficits
 Complete loss of episodic memory
– Events/People since operation
Location of new home
Rey figure: copy but not recalled
 Semantic memory
– Language essentially frozen in 50’s (Gabrieli et al.
1988)
Exceptions: ayatollah, rock ‘n roll
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HM – severe anterograde amnesia
Anterograde amnesia – since lesion
– Suggests encoding deficit
Retrograde amnesia – prior to lesion
anterograde
1/9/1953
Memory
retrograde
1945
1950
1955
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HM working memory
Intact working memory
– Normal digit span (remembering numbers)
– Wickelgren (1968) showed rate of forgetting
within normal range
– Unless interrupted (constant rehearsal)
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HM procedural memory
Intact procedural memory
Can learn new motor tasks
– Mirror tracing task (Milner 1962, 1965)
– Pursuit rotor tracing (Corkin, 1968)
– Implicitly familiar w testing equipment
– Anterograde amnesics can learn new piano
pieces (Starr & Phillips, 1970)
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HM implicit memory
Perhaps procedural tasks tap
‘implicit’ memory – HM has
deficit of ‘explicit’ memory
Milner et al (1968) showed HM
learned Gollin incomplete
picture task
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HM implicit memory
HM has also implicitly learned Tower of
Hanoi game (Cohen, 1984).
Can not remember playing, but solves
quickly.
Start Position
Goal 2 (2 moves)
Goal 10 (5 moves)
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Memento – Amnesia in Film Noir
Guy Pierce

Sammy Jenkins
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HM
Temporally graded retrograde amnesia
1/9/1953
Memory
– Old memories (childhood) OK
– Memories immediately before lesion lost
– Forgot death of favourite uncle in 1950
– Suggests consolidation takes time
1945
1950
1955
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How long does consolidation require?
Testing retrograde amnesia.
– HM: photos of celebrities suggest retrograde
amnesia spans decades, with more distant
memories relatively preserved (MarslenWilson & Teuber, 1975)
PZ – Butters & Cermak (1986)
– Wrote autobiography
– Test personal memories
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Medial Temporal Lobe Memory
MTL patients
– Short term memory intact
– Old long term memory intact
– Suggests ‘consolidation’ deficit
‘Encoding’ deficit, retrieval intact
– See Warrington & Weiskrantz for alternate view
Unable to create new LTM
LTM formation requires years?
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Anatomy
Anterograde amnesia follows damage to
medial temporal lobe or connected
regions.
MTL or diencephalic structures like
thalamus and mamillary bodies
E.G. NA had fencing foil in nose
– Accident in 1960
– Diencephalic damage
– Similar to HM, though less retrograde
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Anterograde Amnesia
Similar deficits with damage anywhere in Papez circuit.
Fornix (Squire’s
Patient)
Mammillary body
(Korsakoff Patients)
Hippocampal formation - HM
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Hippocampus (T1 MRI)
Folded shape
seen in coronal
image.
Here: healthy
individual
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HM’s lesion
 Surgeon report describes removal of entire
hippocampus (Scoville & Milner, 1957).
 Recent MRI (Corkin et al., 1997) study suggests
posterior hippocampus is present (though atrophied).
Scoville & Milner 1957
Corkin et al. 1997
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HM’s lesion
 Corkin et al. (1997)
 bilaterally symmetrical
–
–
–
–
medial temporal pole
most of the amygdaloid complex
most or all of the entorhinal cortex
anterior half of hippocampal formation (dentate gyrus, hippocampus,
and subicular complex)
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Memory – primacy and recency
 People often remember the first few and last few items in
long lists
 First words: primacy – most rehearsal
 Final words: recency – least interference
– Clearly easier: you do not have to remember as long
% recall
 These are thought to reflect different processes
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Item Number
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9 10
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Amnesics show no primacy effect
% recall
Patients like HM remember last few
words (when not interrupted)
Recency effect intact
Primacy effect gone: no encoding benefit
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Item Number
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Memory
Are primacy and recency effects different
processes
Maybe recency is simply easier
Evidence would come from patients who
show an opposite pattern of effects:
– Primacy intact
– Recency impaired
These patients would provide a ‘double
dissociation’
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Primacy and recency
Short term
(working)
memory
% recall
Long term
memory
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Item Number
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Patient KF
% recall
Shallice & Warrington (1970)
Primacy effect intact
Recency effect impaired
Complements amnesic patients
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Item Number
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Potential Paradox
Can information get into long term memory if there is
no short term memory?
Short term
memory
% recall
Long term
memory
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Item Number
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Does LTM require STM?
 According to Atkinson & Shiffrin (1968)
– STM rehearsal leads to LTM
– Predicts that LTM will depends on STM
– Can not accommodate Shallice and Warrington’s
patient
Sensory
(iconic)
Memory
Short Term
Memory
Long Term
Memory
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Shallice & Warrington (1970)
 S & W suggest that short term and long term
memory independent from each other.
 Short term memory not required for long term
memory
 Very controversial model
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Baddeley working memory
 STM is encoded by system dedicated to input
– Verbal info: phonological loop
– Visual info: visuo-spatial scratchpad
 LTM is more modality independent
Phonological Loop
Visuo-Spatial
Scratch pad
Phonological Loop
Long Term Memory
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A: Implicit vs explicit memory
 MTL amnesics
– Explicit memory: unable to create
– Implicit memory: relatively intact
 So far: single dissociation
– 2 possibilities:
1. Implicit/Explicit 2 independent systems
2. Implicit simply easier, relies on residual processing of a
single, partially damaged system
– Double dissociation would support claim of 2
independent systems
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B: Gabrieli et al. (1995)
 Patient MS
– 29 year old, right handed male
– Intractable epilepsy: surgery removed right BA 17,18, part of 19.
– Hemianopic (blind in left field)
 Compared to MTL amnesics and healthy controls.
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C: Results
 Explicit memory task
– Shown 24 words, later shown 48 words (24 from 1st phase, 24 new
foils): asked to say if words were previously seen.
– Amnesics poor.
– MS fine.
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D: Conclusion
 Implicit memory: word completion task
– Shown/Heard 24 words ‘stick’, later asked to complete 48 stems, 24 could
be solved with items from 1st phase (‘sti__’) and 24 unrelated stems
(‘sta__’).
– Healthy people show priming effect (faster if solution seen previously).
This effect is much bigger if words were seen (physical match) rather than
heard.
– Amensics show normal priming. Shows implicit memory.
– MS visual priming is no greater than auditory priming. Therefore, shows
no extra benefit for physical match of stem and previously seen word.
Conclusion
Double dissociation
Explicit memory has some distinct processing from
implicit memory.
‘Conceptual’ priming intact in MS, perceptual
priming damaged
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Recollection vs Familiarity Memory
 Is implicit memory really preserved in MTL amnesics?
– Explicit tasks usually much harder:
 ‘Explicit’ Recall: “What was the picture I showed you earlier?” Could have
thousands of answers.
 ‘Implicit’ Recognition: “Which of these two pictures did I show you” only
has two answers, and seeing the correct answer may jog memory.
– Is this a meaningful dissociation? (see Simons & Spiers, 2003)
 Jon and YR have intact Recognition, but impaired recall
– Selective lesions to only hippocampus or fornix
 LG and PH have poor Recognition, even poorer recall
– Damage to hippocampus and surrounding parahippocampal regions
 Both groups show same pattern
– Not a double dissociation
– Harder task impaired for everyone
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Recollection vs Familiarity Memory
 Yonelinas et al. (2002) compare hypoxic patients (H, focal
bilateral damage to hippocampus) to patients with
unilateral but extensive damage to the hippocampus and
surrounding tissue (H+) and controls (C).
– For H group, recall correlated with recognition (below, left)
– Interaction between groups
 H+ poorer at familiarity (poor implicit)
 H poorer at recollection (poor explicit)
– Suggests Double dissociation is real
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Semantic vs. episodic memory
 HM has impaired semantic and episodic
memory:
– Semantic: Language frozen in 1950s (Gabrieli et al.)
– Episodic: poor at remembering events.
 However, his lesions damage both
hippocampus and surrounding temporal lobe.
– What about patients with more selective damage?
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A: Graham et al. 2000
 Graham et al. suggest double dissociation:
– Early Alzheimer's patients
– ‘Semantic dementia’ patients
Alzheimers Patient
Semantic Dementia
Hippocampus atrophy
Temporal lobe atrophy
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B: Test stimuli
 A: Semantic naming task (‘phone’)
– Correct answer: ‘phone’.
Memory tested 30 minutes later:
 B: Episodic memory task
(perceptually identical)
– Correct answer: ‘I saw a phone
earlier’
 C: Episodic memory task
(perceptually different)
– Correct answer: ‘I saw a phone
earlier’.
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C: Semantic naming
Semantic
dementia
patients have
difficulty
naming items.
AD patients are
fine at this task.
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D: Episodic memory
 AD patients
– poor episodic memory.
 SD patients
– OK with identical items
– Poor with perceptually
different (especially if
unable to name item in
picture naming phase).
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E: Conclusions
 Suggests semantic and episodic memory may
be separate.
– Hippocampal formation: encoding episodic
memories
– Temporal lobe: storage of semantic memories.
– Additional support from Vargha-Khadem (1997),
who reports 4 patients with selective hippocampal
damage: all show impaired episodic but intact
semantic memory.
 Note: all sustained hippocampal damage early in life, so
does not necessarily generalize to adult brain.
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Memory & Prefrontal Cortex (PFC)
 PFC damage results in
–
–
–
–
Disinhibition
Impulsiveness
Disorganization
Memory deficits
 Other deficits can hide memory problems
– Less ‘pure’ than MTL amnesia
Note: oribtofrontal cortex subdivided:
•Ventromedial PFC
•Ventrolateral PFC
Memory structure (Squire & Knowlton,
1994)
 Simplified from page 349 of Gazzaniga book
Declarative memory (explicit)
Nondeclarative memory (implicit)
Events (episodic)
Facts (semantic)
Procedural
Perceptual
Experiences
particular to
time/place
World/word,
language
knowledge,
conceptual
priming
Motor,
cognitive
skills
Perceptual
priming
MTL, PFC
MTL, PFC
Basal
ganglia,
cerebellum
Association
cortex
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Interaction of different brain regions
 Lesions in animals and functional imaging suggest
network of regions work together to encode memory.
 Beyond scope of neuropsychology course.
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Spontaneous confabulation
Confabulation syndrome:
– Spontaneously produce confabulations (no
need to make things up, no external trigger)
– Convinced of accuracy of their
confabulations
– Acted on confabulations (indication of
conviction)
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Double dissociation
 Spontaneous and provoked confabulation
dissociate: Schnider et al. (1996), Brain 119,
1365-1375.
 Spontaneous confabulation
– Generate false memories without prompting
– Often whole gist of memory is false
 Provoked confabulation, false recognition:
– Can be seen in healthy adults
– Accidentally report having seen word earlier in list if
it is similar to previous word
– Errors with small details of overall story
Example of spontaneous
confabulator
58-year old woman
Aneurysm of anterior communicating artery.
– Reported: needed to go home to feed her baby
– Her ‘baby’ was 30 years old
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Case 2
48 year old tax accountant
Traumatic damage to orbitofrontal lobe
Left hospital convinced taxi was waiting
to take him to meeting
Consistently thought he had business
meeting
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Reflections
 Ideas tend to be internally consistent but
inaccurate.
 Careful testing shows they are disoriented,
confuse date and time.
 When confronted, often search for
explanations but fail to adapt their ideas
– Patient in Berne convinced he was in Bordeaux.
– Admitted view from window inconsistent with belief.
– Did not change belief.
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Most confabulations about present
– Plausible
– Traced to actual events
Usually accurate regarding old memories
Majority eventually stop confabulating
despite permanent brain injury
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Eliciting confabulations
 Individual is asked if they saw an image before earlier
in run.
 Do not report having seen image if you only saw it in a
previous run.
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Eliciting confabulations
 Both amnesics and confabulators do poorly at
remembering if they have seen an item before.
 Amnesics forget previously seen items.
 Confabulators report having seen an image from
previous set in current set.
 Problem with context, not recognition per se.
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Anatomy of t
Patients who spontaneously confabulate
tend to have orbitofrontal damage (aka
damage to the ventromedial PFC).