Learning and Memory chapter 14

1
Learning and Memory (chapter 14)
2
Learning and Memory

• Memory refers to the storage and retrieval of
  information.
• No absolute boundaries between learning and
  memory.
• Learning and memory may be viewed as a continuum.

3
Early Theories of Memory Storage

• 1915-1950-Engram (Lashley)
• 1950s to present- Short and Long Term Systems
• Hebbs cell assemblies

4
Locating the Engram

• Karl Lashley observed the effects of lesions on
  rats maze learning.
• The larger the amount of cortex damaged, the more
  errors the rats made.

• Lashley believed that the engram was distributed
  across the cortex.

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Memory Processing

• Short-term Memory (STM)
• Limited capacity (7 items)
• Brief duration
• Can be lost without rehearsal
• Long-term Memory (LTM) permanent storage
• Consolidation Process by which rehearsal of
  information in STM results in transfer to LTM

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Unusual Memory Phenomena
KHBS KHOG/AP/Wide World

• Stress enhances
• memory via actions on
• amygdala and
• hippocampus

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Divisions of Long-term Memory
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Reinforcement

• Learning provides a means for us to profit from
  experience-to make responses that provide
  favorable outcomes. When good things happen,
  reinforcement mechanisms in the brain become
  active, and the establishment of synaptic changes
  is facilitated. Where in brain does this happen?

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The Critical Hippocampus

• Important for memory consolidation
• Storage of implicit memory

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In addition to the hippocampal formation, where
are memories stored?

• Inferotemproal cortex an area of secondary
  sensory cortex--long-term visual memory
• Amygdala emotional significance--lesions impair
  fear conditioning
• Prefrontal cortex damage impairs memory for
  temporal order of events and working memory
• Cerebellum and striatum implicit memory of
  sensorimotor learning

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Amnesia

• Amnesia refers to a failure to remember
• Anterograde amnesia involves a difficulty in
  forming new memories for events that occur after
  a brain trauma
• Anterograde amnesia involves a disorder of
  relational learning
• Anterograde amnesia involves a difficulty in
  learning new material
• Retrograde amnesia is an inability to recall
  events that occured prior to the trauma
• Amnesia can be temporary or permanent

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Types of Amnesia
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Hippocampal Damage and Amnesia

• Severe anterograde amnesia follows bilateral
  damage to the hippocampus
• Patient H.M. suffered from severe epilepsy
• To minimize his epilepsy, H.M.s surgeons removed
  his medial temporal lobe (including the
  hippocampus)
• Following surgery, H.M. showed severe anterograde
  amnesia
• No retention for events that have occurred since
  1953
• Can recall events that occurred prior to 1953
• H.M.s amnesia was attributed to hippocampal
  damage

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Patient H.M. and Memory

• Large areas of H.M.s temporal lobes were
  surgically removed.
• H.M.s personality and IQ were not affected.
• H.M. experienced profound anterograde amnesia.

Courtesy Dr. Suzanne Corkin, Massachusetts
Institute of Technology
15
H.M.s Memories Are Not Equally Affected

• Short-term memory allowed H.M. to converse.
• H.M. retained the ability to learn procedural
  tasks.
• H.M.s deficits appear in explicit memory tasks.

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The Diencephalon and Memory Patient N.A.

• A fencing foil produced a lesion to N.A.s left
  dorsomedial thalamus.
• N.A. experienced profound anterograde amnesia and
  some retrograde amnesia.
• N.A.s memory loss was similar to H. M.s.

Courtesy L.R. Squire, University of California
San Diego
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The Diencephalon and Memory

• Korsakoffs patients show anterograde and
  retrograde amnesia.
• Thiamine deficiencies result from chronic
  alcoholism.
• Untreated thiamine deficiencies damage
  dorsomedial thalamus and mamillary bodies.
• Monkeys with lesions in the dorsomedial thalamus
  or mamillary bodies have difficulties with the
  DNMS test.
• Temporal-diencephalic circuits may process
  long-term memories.

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Memory and Normal Aging

• In healthy adults, most measures of cognitive
  ability remain stable.
• Memory loss may accompany changes in brain
  systems that utilize the neurotransmitter
  acetylcholine (ACh).
• Attaining an above-average education engaging in
  complex, non-routine professions and earning
  high income appear to protect against cognitive
  decline.

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Other Forms of Amnesia

• Alzheimers Disease (basal forebrain)
• Concussion (PTA)
• Electroconvulsive shock (ECS)

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Implicit Memory Reflexive GillWithdrawal in
Aplysia

• Sensitization
• Habituation

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The Anatomy of the Hippocampus
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LTP and the NMDA Receptor
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The Hippocampus and Human Memory

• The right hippocampus is active during spatial
  memory processing and the left hippocampus is
  active during verbal memory processing.
• Rostral portions of the hippocampus are more
  active during encoding, and caudal portions are
  active during retrieval.
• The hippocampus does not store memories, but
  transfers them from short to long-term storage.