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– 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– 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