BIOLOGICAL BASIS OF MEMORY

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BIOLOGICAL BASIS OF MEMORY
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Biological Basis of Memory
Karl Lashley searched for a localized memory
trace or engram
Believed that memory was localized specific
memory stored in a specific area. Removed parts
of rats cerebral cortex but found no one area
contained the memory of the maze Found that
maze-learning in rats was distributed throughout
the brain
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Memory and the Brain

• Play The Locus of Learning and Memory (628)
  Module 16 from The Brain Teaching Modules (2nd
  edition).
• Watch first 3 minutes on Lashleys Experiment and
  if time view Penfields experiment why it was
  flawed.

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Biological Basis of Memory

• Thought that cerebellum was changed after
  classically conditioning a rabbit to blink to a
  tone. He was right!
• Removing this area caused the rabbit to no longer
  blink to a tone but only reflexively. Shows
  localized memory.
• This did not work for complex behaviors like
  running a maze, which seem to be distributed

Richard Thompson Reflexive Behaviors are
localized in the cerebellum
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Biological Basis of Memory

• fMRI shows that when people memorized the label
  dog with the sound of a bark the auditory
  cortex activated when they retrieved it.
• Those memorized the label dog to a picture
  activated their visual cortex when they retrieved
  it.
• Retrieving a memory reactivates the sensory area
  of the cortex that was involved in the initial
  perception of the event. (See images on pg. 268)

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New Memories in a Snail

• Aplysiaa sea snail was used to study how
  memories can change neurons

Eric Kandel
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Kandels Sea Snail Experiment

• Eric Kandel studied neural changes that took
  place in Aplysia, a sea snail. Click HERE to
  view it (4 min)
• Squirted it with water followed by an electric
  shock that classically conditioned it to
  withdrawal its gills next time it was squirted.
• This changed the three neuron circuit in the
  snail.
• Function of the neuron changed with increase in
  the amount of the neurotransmitter produced by
  the neuron.
• Structure of the neuron changed with the number
  of interconnecting dendrites and axon terminals
  increasing allowing for more communication points
  (synapses).

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Long-Term Potentiation

• Two possible changes should occur in the neurons
  in forming memories.
• Functioning of neurons in the brain could change
• Structure of the neurons could change.
• These increase the neurons firing potential
• Kandels experiment shows this.
• Believed to be the neural basis of learning and
  memory

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Severe Memory Loss

• Amnesiasevere memory loss
• 3 Major Types
• Retrograde Amnesia
• Anterograde Amnesia
• Infantile Amnesia

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Retrograde amnesia

• Retrograde amnesiainability to remember PAST
  episodic information common after head injury
• Reason for this is it may disrupt
• Memory Consolidation gradual, physical process
  of converting a long-term memory to a stable and
  enduring memory code.
• If disturbed before the process is complete,
  memory could be lost.
• Sleep seems to be when most memory consolidation
  occurs

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Anterograde amnesia

• Anterograde amnesiainability to form NEW
  memories related to hippocampus damage
• Shows that hippocampus must be used in the
  encoding of new memories and transferring them
  from STM to LTM.
• Implicit memories like procedural memories do
  still occur showing that these may not involve
  the hippocampus but knowing they are there
  (explicit memory) does not work showing the
  hippocampus is involved in these.

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Infantile Amnesia

• Infantile Amnesia Inability to recall events
  from the first few years of life.
• Possible Reasons for this
• Too many differences between the world of an
  infant and ours for us to be able to make
  connections or retrieval cues to retrieve them
  (encoding specificity principle).
• Hippocampus is still developing so they cannot
  form new LTM but they can make procedural
  memories.
• One reason adults typically recall little of
  their first three years of life is that during
  infancy they were unable to verbally label most
  of their experiences (semantically encode the
  info).

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Brain Structures Involved in Memory
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Emotions the Amygdala

• Amygdala may help in formation of emotional
  memories.
• Watch Enhancing Memory (750) to see how research
  is showing this. Click below.

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Evidence for Separate Implicit/Explicit Systems

• Neurophysiological evidence
• Patient H.M. (Henry Gustav Molaison)
• life-threatening seizures originating in temporal
  lobe
• surgically removed portions of temporal lobe

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Temporal Lobe

• Includes
• hippocampus
• Amygdala
• Verbal information is stored in the left
  hippocampus and
• Visual designs are stored in the right hippocampus

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Patient H.M.

• Click HERE for a video on H.M. (10 Min)
• Surgery was effective in reducing seizures
• BUT, had other side effects as well
• Can remember explicit memories acquired before
  the surgery
• e.g., old addresses, normal vocabulary
• Cannot form NEW explicit memories
• e.g., remembering the name of someone he met 30
  minutes prior
• cannot name new world leaders or performers
• can recognize a picture of himself from before
  his surgery but not from after and doesnt
  recognize himself in a mirror

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Patient H.M.

• H.M. has severe explicit / declarative memory
  disorder
• H.M. is almost normal on procedural or implicit
  memory tasks including priming, classical
  conditioning, and learning motor skills
• When given the same logical puzzle to solve for
  several days in a row, H. M. was able to solve
  the puzzle more quickly each day.
• This shows that explicit memory depends upon the
  temporal lobes and implicit does not

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Patient H.M. Summary

• Temporal lobe damage led to deficits in explicit,
  but not implicit memory
• H.M. had both episodic and semantic memory
  deficits
• Damage to the hippocampus alone produces
  episodic, but not semantic memory deficits
• Why did H.M. show both types of explicit memory
  deficits?
• He had damage not only to hippocampus, but to
  other structures as well

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Memory and the Hippocampus

• Damage to the hippocampus would result in the
  inability to form new explicit memories, but the
  ability to remember the skills of implicit
  memories

• To view someone with this damage checkout the
  video by clicking on it (738)

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Memory and the Hippocampus
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Hippocampus and Memory

• Play Living with Amnesia The Hippocampus and
  Memory (1035) Module 18 from The Brain
  Teaching Modules (2nd edition).
• Watch if Time Allows.

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Aging and Memory

• Studies have found that the ability to recall new
  information, unaided by clues, declines with age,
  
• But the ability to recognize new information, as
  in a multiple-choice question, does not.
• Elderly may need more time to retrieve memories
  but still can do as well as a young person.

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Culture Memory

• Levy and Langer study of cultural views of aging
  show that societys expectation that older people
  will have poorer memories can be a
  self-fulfilling prophecy.
• In cultures where that is not believed (Asia) the
  elderly show memories just as good as the young.

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Think your memory is something special?