Memory and its Disorders: The Three Amnesias Russell M. Bauer, Ph.D. University of Florida Human Higher Cortical Function March 24, 2008
The Three Amnesias Russell M. Bauer, Ph.D. (DON’T BELIEVE HIS LIES)
Where’s the Lesion? Patient presents to you with memory complaints. Where’s the lesion? Answer: Above the cervical vertebrae.
Where’s the Lesion? Patient presents to you with a severe and profound impairment in the ability to remember new information that disables them in everyday life. Where’s the lesion? Answer: In an extended memory system that involves a cortical-subcortical network including the medial temporal lobe, thalamus, basal forebrain, and their interconnections
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
Multiple Forms of Memory Recollection (deliberate, conscious) Familiarity (not deliberate or conscoius)
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) MCI/Early AD
Temporal Lobe Pathology Associated with Herpes Simplex Encephalitis
Patterns of Atrophy in Subtypes of MCI Amnestic-Single Domain (88) Amnestic- Multiple Domain (25) Nonamnestic- Single Domain (25) Nonamnestic- Multiple Domain (7) Whitwell, et al. (2007). Arch Neurol, 64(8),
The Case of Henry M (H.M.)
Bauer, Grande, & Valenstein, 2003
Integrated Circuitry Linking Temporal, Diencephalic, and Basal Forebrain Regions
Hippocampus Mammillary Bodies Anterior Thalamus Cingulate Gyrus Fornix Mamillothalamic Tract Amygdala Dorsomedial Thalamus Orbitofrontal Uncus Two Limbic Circuits Medial (Papez) Lateral Amygdalofugal pathways
DG CA3 CA1 subic
Classical Trisynaptic Circuit
Bauer, Grande, & Valenstein, 2003
<100 each 2 x 10 3 each
Long-Term Potentiation (LTP)
Delayed Nonmatching to Sample
Delayed Nonmatching to Sample, multiple trials, trial-unique objects
6-8 weeks postsurgery2 years postsurgery
Zola-Morgan & Squire, 1990 Anterior Posterior
Bauer, Grande, & Valenstein, 2003
Zola-Morgan & Squire, 1990
Murray & Richmond, Curr Opin Neurobiol, 2001
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
Figure 3. Anatomy of the MTL region. (a) Approximate locations of the hippocampus (red), the PRc (blue) and the PHc (green) shown on T1- weighted magnetic resonance images. (b) Representation of the anatomical connections among, and the proposed roles of, the hippocampus, PRc and PHc in episodic memory according to the BIC model. The arrow between the PRc and PHc indicates the anatomic connection between the two regions; the PRc receives more inputs from the PHc than vice versa. The connections shown here are based on results from anatomical studies of rats and monkeys. Diana, Yonelinas, and Ranganath, TICS, 2007) Recollection v. Familiarity
Figure 1. Activation of MTL subregions in studies of recollection and/or familiarity. Shown is the percentage of contrasts of each type (recollection, familiarity or associative recognition) in which activation was reported for the hippocampus, the posterior parahippocampal gyrus (PPHG) and the anterior parahippocampal gyrus (APHG). Data are summarized from Tables 1 and 2. Diana, Yonelinas, and Ranganath, TICS, 2007) Recollection v. Familiarity
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 the Two-system theory of amnesia Medial (Papez) Lateral Amygdalofugal pathways PRPH
Integrated Circuitry Linking Temporal, Diencephalic, and Basal Forebrain Regions
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
Hippocampal Damage: Hypoxic Injury Basal Forebrain Damage due to ACoA Rupture Myers, et al. (2006). Neuropsychologia, 44,
Qualitative Differences between MTL and ACoA patients in conditioned reversal (Myers, et al., 2006) Cheese on right if background is light; on left if dark (reversal = opposite) AcquisitionReversal
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
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 PRPH
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