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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 impairedIntelligence, 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 impairedIntelligence, attention...
Recency vs Primacy
• Amnesia patients exhibit recency effect but not primacy effect
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Long-termmemory
Short-termmemory
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 impairedIntelligence, 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
• 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
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
Proposed types of memory
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.
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Control brain 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
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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.
• Mirror drawing task– H.M. improved with
repeated training.
– Procedural memory is intact
– He cannot recall ever having performed this task before 0
10
20
30
40
Attempts each daynumber of errors per attempt
Day 1 Day 2 Day3
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)
Memory recall ability
Recent Remote
Age of memory
recall performance
H.M.
Control
N.A.
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, well-built 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