Download Amnesia - What is it?

Amnesia - What is it?
A selective disruption of the processes
underlying long-term memory
Short-term and sensory memory are
typically functional
Other cognitive functions are not impaired
Intelligence, attention...
Amnesia - What is it?
A selective disruption of the processes
underlying long-term memory
Short-term and sensory memory are
typically functional
Other cognitive functions are not impaired
Intelligence, attention...
Recency vs Primacy
• Amnesia patients exhibit recency effect but
not primacy effect
Long-term
memory
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Short-term
memory
Amnesia - What is it?
A selective disruption of the processes
underlying long-term memory
Short-term and sensory memory are
typically functional
Other cognitive functions are not impaired
Intelligence, attention...
Retrograde & Anterograde
• Retrograde amnesia - Loss of information
that was learned before the onset of amnesia
• Anterograde amnesia - inability to learn
new information after the onset of amnesia
• Both can occur in the same patient and
commonly do
Retrograde & Anterograde
• Retrograde amnesia - Loss of information
that was learned before the onset of amnesia
• Anterograde amnesia - inability to learn
new information after the onset of amnesia
• Both can occur in the same patient and
commonly do
Causes of Amnesia
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Concussion
Migraines
Hypoglycemia
Epilepsy
Electroconvulsive shock therapy
Specific brain lesions (i.e. surgical removal)
Ischemic events
Drugs (esp. anesthetics)
Infection
Psychological
Nutritional deficiency
Types of memory
Proposed types of memory
Fact memory
Skill memory
Declarative
Non-declarative (Procedural)
Memory
Habit
Explicit
Implicit
Knowing that
Knowing How
Cognitive mediation
Semantic
Conscious recollection
Skills
Elaboration
Integration
Memory with record
Memory without record
Autobiographical
Perceptual
representational
Dispositional
Vertical association
Horizontal association
Locale
Taxon
Episodic
Semantic
Working
Reference
Brain regions associated with
human amnesia
• Diencephalic amnesia - damage to the
medial thalamus and mamillary nuclei
• Medial temporal lobe amnesia - damage to
the hippocampal formation, uncus,
amygdala, and surrounding cortical areas
Brain regions associated with
human amnesia
• Diencephalic amnesia - damage to the
medial thalamus and mamillary nuclei
• Medial temporal lobe amnesia - damage to
the hippocampal formation, uncus,
amygdala, and surrounding cortical areas
Diencephalic Amnesia
• Damage to the medial
thalamus and/or
mamillary bodies
– stroke
• Korsakoff’s syndrome
– Caused by thiamine
deficiency as a result
of chronic alcoholism
Korsakoff’s symptoms
• Anterograde amnesia
• Retrograde amnesia
– Covers most of the adult life
• Lack of insight
– Typically unaware of memory
problems
• Confabulation
– Patient makes up stories to fill
in the past
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Medial Temporal lobe amnesia
• Hippocampus is most important site of
damage
Case H.M.
• Epileptic patient
• Had medial temporal lobes removed to stop
seizures
• Seizures were reduced but H.M. became severely
amnesiac.
Case H.M.
• His intelligence is above normal
– IQ = 112
• Performs normally on all tests of short-term
memory
• Selective long-term memory impairment
Case H.M.
Control brain
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H.M.
Case H.M.
• Memory impairment for recent events
– spans the 3 years prior to his surgery
• Capable of recalling childhood memories
• Anterograde amnesia was initially thought
to be global (all types of memory)
• later discovered that certain types of
learning are intact
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Case H.M.
• Grave memory impairment for recent events
– spans the 3 years prior to his surgery
• Capable of recalling childhood memories
• Anterograde amnesia was initially thought
to be global (all types of memory)
• later discovered that certain types of
learning are intact
Case H.M.
• Priming still works
• H.M. can still form procedural memories
Case H.M.
• The Gollin incomplete picture test
– subjects asked to identify the object
– pictures are shown in sequence from least to
most clear
– shown the same images at a later date
– both amnesiacs and control subjects identify the
object at an earlier stage
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Case H.M.
• Mirror drawing task.
– Trace figure while looking in a mirror
– Control subjects get better at this with repetitive
training.
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Case H.M.
– H.M. improved with
repeated training.
– Procedural memory is
intact
– He cannot recall ever
having performed this
task before
number of errors per attempt
• Mirror drawing task
40
Day 1
Day 2
Day3
30
20
10
0
Attempts each day
Case H.M.
– Doesn’t remember the death of his father
– Can’t remember or describe his job
– Doesn’t remember his examiners
Case H.M.
• According to our memory dichotomies,
what type of memory is the medial temporal
lobe (especially the hippocampus)
responsible for?
Types of memory
Case H.M.
• H.M.s Retrograde amnesia is temporally graded
– remote memory is spared but recent memory is lost
• Not all amnesia patients show this pattern
– V.C., N.A. have extensive retrograde amnesia (flat
gradient)
recall performance
Memory recall ability
H.M.
Control
N.A.
Recent
Remote
Age of memory
Lessons from amnesia
• Existence of Multiple memory systems
• Localization of cognitive functions
S.
• “Photographic” extreme memory ability (a
mnemonist)
• Able to recall complex test stimuli
S.
• “Photographic” extreme memory ability (a
mnemonist)
• Able to recall complex test stimuli
• S. used two “strategies” or abilities typical of
mnemonists:
– rich synesthesia-like quality to his perception of stimuli
- leads to stronger associative links
– vivid and elaborate mental imagery of things he should
remember
S.
• “ Even numbers remind me of images.
Take the number 1. This is a proud, wellbuilt man; 2 is a high-spirited woman; 3 a
gloomy person (shy, I don’t Know); 6 a man
with a swollen foot...”
Luria, A.R. The mind of a mnemonist. 1968
Luria, A.R. The man with a shattered world. 1972