Module 12.1: Learning, Memory, and Amnesia

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Module 12.1Learning, Memory, and Amnesia
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Learning, Memory, and Amnesia

• An early influential idea regarding localized
  representations of memory in the brain suggested
  physical changes occur when we learn something
  new.
• One popular idea was that connections grow
  between areas of the brain.

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Learning, Memory, and Amnesia

• Ivan Pavlov researched classical conditioning in
  which pairing of two stimuli changes the response
  to one of them.
• Presentation of a conditioned stimulus (CS) is
  paired with an unconditioned stimulus (UCS).
• Automatically results in an unconditioned
  response (UCR).
• After several pairings, response can be elicited
  by the CS without the UCS, which is known as a
  conditioned response (CR).

Ivan Pavlov (1849-1936)
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Learning, Memory, and Amnesia

• In operant conditioning, responses are followed
  by reinforcement or punishment that either
  strengthen or weaken a behavior.
• Reinforcers are events that increase the
  probability that the response will occur again.
• Punishment are events that decrease the
  probability that the response will occur again.

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Learning, Memory, and Amnesia

• Pavlov believed that conditioning strengthened
  connections between the CS center and UCS center
  in the brain.
• Karl Lashley set out to prove this by searching
  for such engrams, or physical representations of
  what had been learned.
• Believed that a knife cut should abolish the
  newly learned response.

Karl Lashley (1890-1958)
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Learning, Memory, and Amnesia

• Lashleys studies attempted to see if disrupting
  certain connections between cortical brain areas
  would disrupt abilities to learn associations.
• Found that learning and memory did not depend on
  connections across the cortex
• Also found that learning did not depend on a
  single area of the cortex.

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Learning, Memory, and Amnesia

• Lashley proposed two key principles about the
  nervous system
• Equipotentiality all parts of the cortex
  contribute equally to complex functioning
  behaviors (e.g. learning)
• Mass action the cortex works as a whole, not as
  solitary isolated units.

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Learning, Memory, and Amnesia

• Research by Richard F. Thompson and colleagues
  focused on the cerebellums role in classical
  conditioning.
• During an eye-blink conditioning task in rabbits,
  changes were recorded in cells of the lateral
  interpositus nucleus (LIP).

Richard F. Thompson (1930-2014)
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Learning, Memory, and Amnesia

• Suppression of activity (through application of
  drugs or cooling the LIP) led to a condition in
  which the subject displayed no previous learning.
• As suppression wore off, the animal began to
  learn at the same speed as animals that had no
  previous training.
• Red nucleus of the midbrain found to temporarily
  suppress a response, but not learning

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Learning, Memory, and Amnesia

• Donald Hebb (1904-1985) differentiated between
  two types of memory(1949)

• Short-term memory (STM) memory of events that
  have just occurred
• Limited capacity
• Fades quickly
• Not affected by cues
• Long-term memory (LTM) memory of events from
  previous times
• Unlimited capacity
• Memories persist over time
• Can be stimulated with a cue

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Learning, Memory, and Amnesia

• Later research weakened the distinction between
  STM and LTM.
• Some memories do not qualify as distinctly
  short-term or long-term.
• Working Memory
• Proposed by Baddeley Hitch (1994) as an
  alternative to short-term memory
• Emphasis on temporary storage of information to
  actively attend to it and work on it for a period
  of time

Alan Baddeley Graham Hitch
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Learning, Memory, and Amnesia

• Three major components of working memory include
• Phonological loop Stores auditory input
• Visuospatial sketchpad Stores visual input
• Central Executive Directs attention and
  determines which items to store

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Learning, Memory, and Amnesia

• The delayed response task is a test of working
  memory which requires responding to a stimulus
  that one heard or saw a short while earlier.
• Increased activity in the prefrontal cortex
  during the delay indicates storing of the memory.
• The stronger the activation, the better the
  performance.

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Learning, Memory, and Amnesia

• Older people often have impairments in working
  memory.
• Changes in the prefrontal cortex assumed to be
  the cause.
• Declining activity of the prefrontal cortex in
  the elderly is associated with decreasing memory.
• Increased activity is indicative of compensation
  for other regions in the brain.

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Learning, Memory, and Amnesia

• Amnesia is the loss of memory.
• Studies on amnesia help to clarify different
  kinds of memories and their mechanisms.
• Different areas of the hippocampus are active
  during memory formation and retrieval.
• Damage results in amnesia.

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Learning, Memory, and Amnesia

• Patient HM is a famous case study in psychology
  who had his hippocampus removed to prevent
  epileptic seizures.
• Afterwards HM had great difficulty forming new
  long-term memories.
• STM or working memory remained intact.
• Suggested that the hippocampus is vital for the
  formation of new long-term memories.

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Learning, Memory, and Amnesia

• Patient HM showed massive anterograde amnesia
  after the surgery.
• Two major types of amnesia include
• Anterograde amnesia the loss of the ability to
  form new memory after the brain damage occurred.
• Retrograde amnesia the loss of memory events
  prior to the occurrence of the brain damage.

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Learning, Memory, and Amnesia

• Patient HM had difficulty with declarative and
  episodic memory.
• Episodic memory ability to recall single events
• Declarative memory ability to put a memory into
  words
• HMs procedural memory remained intact.
• Procedural memory ability to develop motor
  skills (remembering or learning how to do things)

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Learning, Memory, and Amnesia

• HM also displayed greater implicit than
  explicit memory.
• Explicit memory deliberate recall of
  information that one recognizes as a memory
• Implicit memory the influence of recent
  experience on behavior without realizing one is
  using memory

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Learning, Memory, and Amnesia

• Hippocampus activity is more associated with
  memory performance than is the size.
• The hippocampus is
• critical for declarative (especially episodic)
  memory functioning
• especially important for spatial memory
• especially important for configural learning and
  binding.

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Learning, Memory, and Amnesia

• Research in the role of the hippocampus in
  episodic memory shows damage impairs abilities on
  two types of tasks
• Delayed matching-to-sample tasks a subject sees
  an object and must later choose the object that
  matches.
• Delayed non-matching-to-sample tasks subject
  sees an object and must later choose the object
  that is different than the sample.

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Learning, Memory, and Amnesia

• Damage to the hippocampus impairs abilities on
  spatial tasks such as
• Radial mazes a subject must navigate a maze
  that has eight or more arms with a reinforcer at
  the end.
• Morris search task a rat must swim through
  murky water to find a rest platform just
  underneath the surface.

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Learning, Memory, and Amnesia

• Hippocampus damage impairs configural learning
  and binding
• Configural learning learning in which the
  meaning of a stimulus depends on what other
  stimuli are paired with it.
• Animals with damage can learn configural tasks
  but learning is slow.
• Indicates hippocampus is not necessary for
  configural learning, but is involved.

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Learning, Memory, and Amnesia

• Evidence suggests that the hippocampus is
  important in the process of consolidation.
• Consolidation is the process of strengthening
  short-term memories into long-term memories.
• Damage to the hippocampus impairs recent learning
  more than older learning.
• The more consolidated a memory becomes, the less
  it depends on the hippocampus.

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Learning, Memory, and Amnesia

• Consolidation is influenced by the passage of
  time and emotions.
• Small to moderate amounts of cortisol activate
  the amygdala and hippocampus where they enhance
  storage and consolidation of recent experiences.
• Prolonged stress impairs memory.

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Learning, Memory, and Amnesia

• Different kinds of brain damage result in
  different types of amnesia.
• Two common types of brain damage include
• Korsakoffs syndrome
• Alzheimers disease

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Learning, Memory, and Amnesia

• Korsakoffs syndrome prolonged thiamine
  (vitamin B1) deficiency impedes the ability of
  the brain to metabolize glucose.
• Leads to loss or shrinkage of neurons in the
  brain
• Often due to chronic alcoholism
• Symptoms include apathy, confusion, and
  forgetting and confabulation (taking guesses to
  fill in gaps in memory).

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Learning, Memory, and Amnesia

• Alzheimers disease is associated with a
  gradually progressive loss of memory often
  occurring in old age.
• Affects 50 of people over 85.
• Early onset seems to be influenced by genes, but
  99 of cases are late onset.
• About half of all patients with late onset have
  no known relative with the disease.

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Learning, Memory, and Amnesia

• Alzheimers disease is associated with an
  accumulation and clumping of the following brain
  proteins

• Amyloid beta protein 42 which produces widespread
  atrophy of the cerebral cortex, hippocampus and
  other areas.
• An abnormal form of the tau protein, part of the
  intracellular support system of neurons.

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Learning, Memory, and Amnesia

• Accumulation of amyloid beta and tau proteins
  results in
• Plaques structures formed from degenerating
  neurons
• Tangles structures formed from degenerating
  structures within a neuronal body

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Learning, Memory, and Amnesia

• A major area of damage is the basal forebrain and
  treatment includes enhancing acetylcholine
  activity.

Donepezil (Aricept)cholinesterase inhibitor
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Learning, Memory, and Amnesia

• Lessons from studying amnesiac patients include
• One can be deficient in several different aspects
  of memory.
• There are independent kinds of memory.
• Various kinds of memory depend on different brain
  areas.

Head Shot In this diffusion spectrum image,
fiber bundles are color coded according to their
directions of impulse transmission. The Human
Connectome Project uses diffusion spectrum and
other cutting-edge neuroimaging techniques to map
fiber pathways in the normal human brain.