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

Patients & Syndromes HM-mediotemporal lobe NA--thalamus Korsakoffs-thalamus & hypothalamus

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

Memory Declarative: Explicit Easy to form, easy to lose 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

Conscious Recollection Only declarative memories & not non-declarative memories

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)

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

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?

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

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

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

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

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

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

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

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

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

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

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