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Multiple Forms of Memory
“Core” Features of Amnesia
anterograde amnesia: defect in new
learning
retrograde amnesia/remote memory
disturbance: defect in retrieving old
memories
spared memory abilities: attention span,
psychometric intelligence, and
‘nondeclarative’ forms of memory are
generally spared
The Human Amnesic Syndrome
• Impaired new learning (anterograde amnesia),
exacerbated by increasing retention delay
• Impaired recollection of events learned prior to onset
of amnesia (retrograde amnesia), often in temporally
graded fashion
• Not limited to one sensory modality or type of
material
• Normal IQ, attention span, “nondeclarative” forms of
memory
Clinically Relevant Dimensions
of Human Memory Performance
Immediate-recent-remote
Encoding-storage-retrieval
Material, modality specificity
Tests vs. processes
Encoding
• Definition: process of transforming to-be
remembered in formation into memorable and
retrievable form
– Encoding I: bringing information-processing
capacity to bear on stimuli
– Encoding II: ability to use the results of E-1
mnemonically
• Relevance: levels-of-processing accounts of
memory (memory as by-product of information
processing)
• Clinical manifestation: poor immediate
(superspan) recall
Consolidation/Storage
• definition: process of making new
memories permanent
• basis: anatomic and physiological changes at
cellular level; hippocampal system important
• when? during study-test interval
• duration: hours? days? years?
• clinical symptom: delayed memory <<
immediate memory (forgetting)
Retrieval
• definition: process of locating, selecting,
and activating a memory representation
• basis: re-enactment of pattern of excitation
occurring at encoding
• when? at point of test
• clinical symptom: recall << recognition
(also true of shallow encoding), inconsistent
errors
Medial Temporal Syndromes
• Anoxic-hypoxic syndromes
– cardiac arrest
– CO poisoning
• Amnesia associated with ECT
• CNS Infections (Herpes)
• MTS and complex-partial epilepsy
(material-specific)
• Early AD
Temporal Lobe Pathology Associated
with Herpes Simplex Encephalitis
The Case of
Henry M (H.M.)
Bauer, Grande, & Valenstein, 2003
Integrated Circuitry Linking Temporal,
Diencephalic, and Basal Forebrain Regions
Two Limbic Circuits
Anterior
Thalamus
Cingulate
Gyrus
Dorsomedial
Thalamus
Mamillothalamic
Tract
Mammilary
Bodies
Fornix
Hippocampus
Medial (Papez)
Orbitofrontal
Amygdalofugal
pathways
Uncus
Amygdala
Lateral
CA3
CA1
DG
subic
Delayed Nonmatching to Sample
Delayed Nonmatching to Sample, multiple
trials, trial-unique objects
6-8 weeks postsurgery
2 years postsurgery
Zola-Morgan & Squire, 1990
Bauer, Grande, &
Valenstein, 2003
Zola-Morgan & Squire, 1990
Two Limbic Circuits and the
Two-system theory of amnesia
Anterior
Thalamus
Cingulate
Gyrus
Dorsomedial
Thalamus
Mamillothalamic
Tract
Mammilary
Bodies
Orbitofrontal
Amygdalofugal
pathways
Fornix
Uncus
Hippocampus
Amygdala
PRPH
Medial (Papez)
Lateral
Diencephalic Syndromes
• Korsakoff Syndrome associated
with ETOH abuse or malabsorption
– prominent encoding deficits
– role of frontal pathology
• Vascular disease
• Thalamic trauma
Mamillary Body Lesions in a case
of Korsakoff’s Disease
Graff-Radford, et al,
1990
Two Limbic Circuits and the
Two-system theory of amnesia
Anterior
Thalamus
Cingulate
Gyrus
Dorsomedial
Thalamus
Mamillothalamic
Tract
Mammilary
Bodies
Fornix
Hippocampus
Medial (Papez)
Orbitofrontal
Amygdalofugal
pathways
Uncus
Amygdala
Lateral
Two Potential Lesion Scenarios in
Diencephalic Amnesia
Basal Forebrain Syndromes
• Anterior Communicating Artery (ACoA)
infarctions
– prominent anterograde, variable retrograde
amnesia
– prominent confabulation
– frontal extension of lesions
• Basal forebrain and cholinergic
projections to hippocampus
Basal Forebrain Anatomy
Two Limbic Circuits
Anterior
Thalamus
Cingulate
Gyrus
Dorsomedial
Thalamus
Mamillothalamic
Tract
Mammilary
Bodies
Fornix
Hippocampus
Medial (Papez)
Orbitofrontal
Amygdalofugal
pathways
Uncus
Amygdala
Lateral
Two Potential Lesion Scenarios in Basal
Forebrain Amnesia
Two Limbic Circuits
Anterior
Thalamus
Cingulate
Gyrus
Dorsomedial
Thalamus
Mamillothalamic
Tract
Mammilary
Bodies
Fornix
Hippocampus
Medial (Papez)
Orbitofrontal
Amygdalofugal
pathways
Uncus
Amygdala
Lateral
Bauer, Grande, & Valenstein, 2003
Key Points
• Extended memory system including
hippocampus, amygdala, and basal forebrain
• We (basically) understand anatomy, now we
need to understand computation
• Notion of distinct subtypes of amnesia
generally less favorable now than 10 years
ago
• Certain structures are ‘wired’ for associational
processing; these structures are reciprocally
connected to cortical processors