Clinically Relevant Functional Neuroanatomy
2: Neuroanatomy of Memory
Russell M. Bauer, Ph.D.University of Florida, USA
Vivian Smith Summer Institute
23 June, 2006
The Three Amnesias
Russell M. Bauer, Ph.D. (DON’T BELIEVE HIS LIES)
Multiple Forms of MemoryMultiple Forms of Memory
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
Integrated Circuitry Linking Temporal, Diencephalic, and Basal Forebrain Regions
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
Hippocampus
Mammilary Bodies
Anterior Thalamus
Cingulate Gyrus
Fornix
Mamillothalamic Tract
Amygdala
Dorsomedial Thalamus
Orbitofrontal
Uncus
Two Limbic Circuits
Medial (Papez) Lateral
Amygdalofugal pathways
DG
CA3CA1
subic
Bauer, Grande, & Valenstein, 2003
Delayed Nonmatching to Sample
Delayed Nonmatching to Sample, multiple trials, trial-unique objects
6-8 weeks postsurgery 2 years postsurgery
Zola-Morgan & Squire, 1990
Anterior Posterior
Bauer, Grande, & Valenstein, 2003
Zola-Morgan & Squire, 1990
Murray & Richmond, Curr Opin Neurobiol, 2001
-perirhinal cortex obviously important in memory, but also apparently important in fine-grained visual discrimination
Hippocampus
Mammillary Bodies
Anterior Thalamus
Cingulate Gyrus
Fornix
Mamillothalamic Tract
Amygdala
Dorsomedial Thalamus
Orbitofrontal
Uncus
Two Limbic Circuits and the Two-system theory of amnesia
Medial (Papez) Lateral
Amygdalofugal pathways
PRPH
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
Lesion Profile in a Case of Thalamic Amnesia
Graff-Radford, et al, 1990
Hippocampus
Mammillary Bodies
Anterior Thalamus
Cingulate Gyrus
Fornix
Mamillothalamic Tract
Amygdala
Dorsomedial Thalamus
Orbitofrontal
Uncus
Two Limbic Circuits and theTwo-system theory of amnesia
Medial (Papez) Lateral
Amygdalofugal pathways
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
Hippocampus
Mammillary Bodies
Anterior Thalamus
Cingulate Gyrus
Fornix
Mamillothalamic Tract
Amygdala
Dorsomedial Thalamus
Orbitofrontal
Uncus
Two Limbic Circuits
Medial (Papez) Lateral
Amygdalofugal pathways
Hippocampus
Mammillary Bodies
Anterior Thalamus
Cingulate Gyrus
Fornix
Mamillothalamic Tract
Amygdala
Dorsomedial Thalamus
Orbitofrontal
Uncus
Two Limbic Circuits
Medial (Papez) Lateral
Amygdalofugal pathways
Bauer, Grande, & Valenstein, 2003
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
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