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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 nondeclarative memories
Declarative Memory
• Essential Anatomy
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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
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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