Learning and Memory Topic Outline

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Learning and Memory Topic Outline

• Learning and Synaptic Plasticity
• Learning and Memory Problems
• Perceptual Learning
• Classical Conditioning
• Instrumental Conditioning and Motor Learning
• Relational Learning

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Learning

• ...relatively permanent changes in behavior
  produced by experience
• Learning involves changes in the nervous system
• Physical/chemical
• Learning allows us to tailor our behaviors to the
  environment allows for adaptation
• Learning involves the motor, sensory, and memory
  systems
• Lashleys engram- physical representation of
  memory

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Forms of Learning

• Perceptual identify objects and situations
• Stimulus-Response connections between stimuli
  and motor responses
• Classical conditioning
• Operant Conditioning
• Motor form new circuits in motor system
• Relational identify connections between stimuli

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Classical Conditioning

• Involves making connections between two forms of
  stimuli
• Unconditional (US) reliably provokes a response
• Response is termed unconditional (UCR)
• Conditional (CS) neutral does not provoke the
  response
• Pair the CS and UCS over many trials
• Does the CS alone produce a response?

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Video The locus of learning and memory
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The Hebb Rule

• Hebb argued that synapses that are active at the
  same time that the postsynaptic neuron fires are
  strengthened over time
• Implies physical changes in the nervous system
• Rosensweig enriched environment studies
• Noted specific changes in brains of enriched rats
• Thicker cortex
• More glial cells
• More Ache (perhaps more ACh?)

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Video Learning as synaptic change
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Long-Term Potentiation

• Cells in entorhinal cortex project via perforant
  path to synapse onto granule cells in the dentate
  gyrus
• LTP procedure electrically stimulate perforant
  path (100 pulses/over a few seconds)
• Then observe postsynaptic potential induced by a
  single pulse given repeatedly over days
• LTP is indexed by gradual increase in PSP size

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Long-Term Potentiation

• LTP requires
• Activation of synapses and depolarization of
  postsynaptic membrane
• LTP involves
• Release of glutamate
• Activation of NMDA receptors in depolarized
  membrane
• Entry of calcium ions

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Mechanisms of LTP

• LTP may result from
• Increased release of transmitter
• Increased number of receptors
• Greater linkage of receptors to ion channel
  openings
• Increased number of synapses
• Other causes?

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Glutamate releaseNMDA receptorsNon-NMDA
rec.Calcium entryNO feedback onto presynaptic
cell
A Biochemical Model of LTP
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Video Living with amnesia
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Pathologies of Memory

• Amnesia vs. forced memories
• Review of cases
• Korsakoffs
• Alzheimers- video later in course
• Concussion
• ECS

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Video memory strategies from an expert.
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Perceptual Learning

• Learning about simple perceptual objects occurs
  in association cortex
• Visual perceptual learning
• Ventral stream what object issues
• Ability to differentiate visual patterns requires
  intact connections between visual cortex and
  inferior temporal cortex
• Dorsal stream where object issues
• PET studies document ventral/dorsal stream
  activation during object- and spatial-memory tasks

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Role of ACh in Learning and Memory

• Deutsch noted that anticholinergic drugs impair
  learning in animals and humans
• Alzheimers disease involves memory loss
• Damage to ACh cells in Alzheimers disease
• Nuc. Basalis--gt neocortex
• Medial septum--gt hippocampus
• Footshock induces ACh release in auditory cortex
  sharpens tone detection

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Classical Conditioning

• Footshock (FS) activates cells in basolateral
  amygdala--gt activates central amygdala
• Central amygdala--gt freezing, autonomic changes
• Tone activates cells in the medial geniculate
• CER learning Tones paired with FS come to
  elicit freezing
• May be due to LTP-like processes in thalamus,
  amygdala
• CER is blocked by AP5 (NMDA antagonist) in
  amygdala

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Reinforcement

• Olds and Milner study
• Electrical stimulation of rat brain induces
  reinforcement
• Responses that produce brain stimulation are
  repeated (e.g. bar press, alley running)
• Dopamine plays a critical role in
  self-stimulation
• Mesolimbic dopamine system
• Ventral tegmentum to accumbens, amygdala, septum
• Mesocortical dopamine system

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Nuc. Accumbens and Reinforcement

• Self-stimulation is supported by electrodes
  placed along mesolimbic path
• Rats will self-inject dopamine agonists directly
  into the nuc. accumbens
• Natural reinforcers increase extracellular
  dopamine levels in nuc. accumbens
• Microdialysis studies
• Drugs of abuse also increase DA release

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DA and Motivated Behaviors

• Natural and conditioned reinforcers may act via
  stimulating DA release in the nuc. accumbens
• Conditioned punishers may reduce DA in nuc.
  accumbens
• Mark et al (1989) after CTA learning, saccharin
  taste reduces DA level in nuc. accumbens

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Carlson - Physiology of Behavior 6/e, Allyn and
Bacon
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Long and Short Term Memory

• STM- (working memory)
• limit is about 7 items.
• Once lost its gone for good.
• Can be selectively impaired.
• Prefrontal cortex
• LTM-
• Unlimited
• Can recall with effort and clues
• Can be selectively impaired
• Distributed storage

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Role of Brain areas in Memory

• Rhinal cortex-medial temporal cortex formation
  of LTM for objects
• Hippocampus consolidation of LTM for spatial
  locations
• Amygdala emotional content?
• Association cortex memory storage?

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Role of Brain areas in Memory

• Cerebellum motor learning
• Prefrontal cortex temporal order of events
• Dorsal medial thalamus linked with medial
  temporal lobe
• Basal forebrain many functions, not just memory