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Memory Systems

Memory Systems. Hippocampus. Hippocampus & Relational Memory. Highly processed information from association cortex areas enter hippocampus Hippocampus integrates them—ties them together and then output is stored in other cortical areas Allows you to retrieve all the information about an event.

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Memory Systems

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  1. Memory Systems Hippocampus

  2. Hippocampus & Relational Memory • Highly processed information from association cortex areas enter hippocampus • Hippocampus integrates them—ties them together and then output is stored in other cortical areas • Allows you to retrieve all the information about an event

  3. Patients & Syndromes • HM-mediotemporal lobe • NA--thalamus • Korsakoffs-thalamus & hypothalamus

  4. Amnesia • Anterograde • Cannot form any new types of memories so always live at time of injury • Retrograde • Cannot recall stored memories for a specific time period

  5. Declarative: Explicit Facts & Events Easy to form, easy to lose Medial Temporal Lobe & Thalamus Non-Declarative: Implicit Takes repetition, hard to lose Procedural Skills & Habits Striatum Classical Conditioning Skeletal Muscles Cerebellum Emotional Responses Amygdala Memory

  6. Conscious Recollection • Only declarative memories & not non-declarative memories

  7. Declarative Memory • Essential Anatomy • Medial Temporal Lobe • Entorhinal and Perirhinal, Parahippocampal Cx • Hippocampus • Fornix to Mammilary Body of Hypothalamus • Anterior & Dorsomedial Thalamus that project to cingulate cx (limbic system)

  8. HM • Had bilateral mediotemporal lobes removed due to epilepsy • Removed amygdala, anterior 2/3 of hippocampus, temporal cortex • Had anterograde amnesia • Studied by Brenda Milner • Could learn by procedural memory but had no recollection of having learned task

  9. Squire & Mishkin • Neuroscientists create an animal model for HM symptoms • Lesioned amygdala, hippocampus and perirhinal cortex in temporal lobe of monkeys and found that they could no longer perform in recognition memory tests • Later showed that perirhinal cortex is most important for new memory; temporary storage? Memory consolidation?

  10. Diencephalon & Memory Processing • Anterior thalamic nucleus • Dorsal Medial Thalamic nucleus • Mammillary bodies in hypothalamus

  11. Dorsal medial thalamic nucleus • Receives input from temporal lobe structures including amygdala & inferiortemporal cortex • Projects to all frontal cortex areas

  12. NA • Air Force technician injured by fencing foil –penetrated the dorsalmedial thalamus • Developed retrograde amnesia of previous 2 years and severe anterograde amnesia • Supports role of thalamus in memory

  13. Lashley • Lashley: 1920s studied rats in maze after cortical lesions • Found that all cortical areas are involved in memory

  14. Hebb, Lashley student • suggested CELL ASSEMBLY = all cells that respond to an external stimulus & are reciprocally interconnected • Neurons that fire together, wire together • 1949 Organization of Behavior • Sensory cortex also stores memory • Led to neural networks computer modeling

  15. Circuit using limbic structures • Hippocampal output axons travel as a bundle, the fornix, to the mammillary bodies of the hypothalamus • Mammillary body axons project to anterior thalamic nucleus

  16. Definitions • Declarative & NonDeclarative • Long term & Short Term • Procedural & Working • Experience Dependent Brain Development • Anterograde and Retrograde Amnesia

  17. Learning & Memory • Adaptations of brain circuitry to life experience • Learning = acquisition of new information or knowledge • Memory = retention of learning

  18. Long Term/Short Term Memory • Long Term: last years but is selective • Short term: last seconds to hours

  19. Memory based on Vision • Should be found in cortical area involved in vision processing • inferiortemporal cortex: higher order processing of visual information—stores memory of previously seen objects • Allows recognition of visual objects • Remember Kluver-Bucy pyschic blind monkeys

  20. Penfield • Neurosurgeon in the 1950’s removed epileptic foci after stimulation • Found that stimulation of temporal lobe in awake patients caused halucinations or memory retrieval

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