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The Three Amnesias

The Three Amnesias. Russell M. Bauer, Ph.D. (DON’T BELIEVE HIS LIES). Multiple Forms of Memory. “Core” Features of Amnesia. anterograde amnesia : defect in new learning retrograde amnesia / remote memory disturbance : defect in retrieving old memories

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The Three Amnesias

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  1. The Three Amnesias Russell M. Bauer, Ph.D. (DON’T BELIEVE HIS LIES)

  2. Multiple Forms of Memory

  3. “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

  4. 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

  5. Clinically Relevant Dimensions of Human Memory Performance Immediate-recent-remote Encoding-storage-retrieval Material, modality specificity Tests vs. processes

  6. 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

  7. 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)

  8. 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

  9. 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

  10. Temporal Lobe Pathology Associated with Herpes Simplex Encephalitis

  11. The Case of Henry M (H.M.)

  12. Bauer, Grande, & Valenstein, 2003

  13. IntegratedCircuitry Linking Temporal, Diencephalic, and Basal Forebrain Regions

  14. Two Limbic Circuits Anterior Thalamus Dorsomedial Thalamus Mamillothalamic Tract Mammilary Bodies Cingulate Gyrus Orbitofrontal Amygdalofugal pathways Fornix Uncus Hippocampus Amygdala Lateral Medial (Papez)

  15. CA3 CA1 DG subic

  16. Delayed Nonmatching to Sample

  17. Delayed Nonmatching to Sample, multiple trials, trial-unique objects

  18. 6-8 weeks postsurgery 2 years postsurgery

  19. Zola-Morgan & Squire, 1990

  20. Bauer, Grande, & Valenstein, 2003

  21. Zola-Morgan & Squire, 1990

  22. Two Limbic Circuits and the Two-system theory of amnesia Anterior Thalamus Dorsomedial Thalamus Mamillothalamic Tract Mammilary Bodies Cingulate Gyrus Orbitofrontal Amygdalofugal pathways Fornix Uncus Hippocampus Amygdala PRPH Lateral Medial (Papez)

  23. Diencephalic Syndromes • Korsakoff Syndromeassociated with ETOH abuse or malabsorption • prominent encoding deficits • role of frontal pathology • Vascular disease • Thalamic trauma

  24. Mamillary Body Lesions in a case of Korsakoff’s Disease

  25. Graff-Radford, et al, 1990

  26. Two Limbic Circuits and the Two-system theory of amnesia Anterior Thalamus Dorsomedial Thalamus Mamillothalamic Tract Mammilary Bodies Cingulate Gyrus Orbitofrontal Amygdalofugal pathways Fornix Uncus Hippocampus Amygdala Lateral Medial (Papez)

  27. Two Potential Lesion Scenarios in Diencephalic Amnesia

  28. 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

  29. Basal Forebrain Anatomy

  30. Two Limbic Circuits Anterior Thalamus Dorsomedial Thalamus Mamillothalamic Tract Mammilary Bodies Cingulate Gyrus Orbitofrontal Amygdalofugal pathways Fornix Uncus Hippocampus Amygdala Lateral Medial (Papez)

  31. Two Potential Lesion Scenarios in Basal Forebrain Amnesia

  32. Two Limbic Circuits Anterior Thalamus Dorsomedial Thalamus Mamillothalamic Tract Mammilary Bodies Cingulate Gyrus Orbitofrontal Amygdalofugal pathways Fornix Uncus Hippocampus Amygdala Lateral Medial (Papez) Bauer, Grande, & Valenstein, 2003

  33. Key Points • Extended memory systemincluding hippocampus, amygdala, and basal forebrain • We (basically) understand anatomy, now we need to understand computation • Notion ofdistinct subtypes of amnesia generally less favorablenow than 10 years ago • Certain structures are‘wired’ for associational processing; these structures are reciprocally connected to cortical processors

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