PSYC 304 Final

• The Neural Basis of Associative Learning

  • Aversive (Fear) and Appetitive Associative Learning
  • Contributions of the Amygdala and Striatum
  • Instrumental learning and conditioned reinforcers

  
• Fear


  An adaptive trait that keeps us away from bad things
• Some stimuli evoke an innate fear response (no learning required)
• Animals or humans with lesions to the amygdala display "fearless"-like behaviours
• With many other harmful things in our environment, we learn to be afraid of them
• Amygdala


  Plays an essential role in learning to be afraid of potentially harmful things
• Pavlovian (Classical) Conditioning


  1. Unconditioned Stimulus (US)

  2. Unconditioned Response (UR)

  3. Conditioned Stimulus (CS)

  4. Conditioned Response (CR)
• Pavlovian conditioning is virtually displayed by all animals
• The CR is also uncontrollable and typically an autonomic response
• Pavlovian conditioning is very long lasting
• The Amygdala and Fear Conditioning


  • Freezing is a natural defensive response for rodents
  • Lesions to amygdala subnuclei abolish increase freezing and autonomic response to the CS
  • Neurons in lateral amygdala show changes in firing to CS that parallels emergence of conditioned response

  
• The Amygdala and Appetitive Conditioning


  • Lesions of the lateral amygdala disrupts conditioned place preference for all types of rewards
  • Reward-associated cues can control our behaviour, sometimes without us being aware

  
• Instrumental Conditioning


  Association with a particular action/motor response and its consequences
• Instrumental Conditioning


  • Regions of the striatum regulate action selection and instrumental conditioning
  • Instrumental learning goes through phases from goal-directed to habitual
• The amygdala sends input to the striatum and can influence instrumental action

  
• Conditioned Reinforcement


  CS light comes on that predicts reward presentation, after learning animals will press lever just for CS light
• Lesions to lateral amygdala disrupts preference for lever that produces the CS
• Taxonomies of Memory


  • Temporal stages of memory storage
  • The hippocampus and memory
  • Types of information stored in memory
  • Studies of hippocampus and memory in animals

  
• Lever presses


  Rats press lever just for CS (light), even though that never gives reward
• Light


  Becomes reinforcing, animals will work for it
• Cash


  The biggest reinforcer in the world (associated with nice things)
• Lesions to lateral amygdala

  Disrupts preference for lever that produces the CS (no conditioned reinforcement)

  
• Yet, they consume reward normally, press levers for food normally
• Cues associated with reward can control our behaviour, even though we may be unaware of their control
• Systems mediating this learning

  The amygdala, and sometimes the striatum

  
• Taxonomies of Memory


  • Temporal stages of memory storage

  
• The hippocampus and memory

  The case of HM

  
• Taxonomies of memory revisited


  • Types of information stored in memory

  
• Encoding


  Getting sensory info into your brain by translating it into a neural code it can understand

  
• Storing


  Retaining information over time. Note that biological memories tend to be more "fuzzy" and fragile

  
• Retrieval


  The active processes of locating and using stored information
• Main points to understand about the neural basis of memory

  • There are multiple forms of memory
  • Different types of memory are regulated by distinct brain regions
  • One type of memory is regulated by interactions between multiple brain regions

  
• Short-term memory


  Information held for short periods while physiological changes needed for long-term memory are made

  
• Short-term memory


  • Limited capacity (7 +/- 2 items)
  • Susceptible to distraction, requires active rehearsal to maintain (very labile, very fragile)
  • Information loss occurs through displacement (something new pushes it out) or through decay
• Long-term memory


  Relatively stable, can last lifetime of the organism
• Long-term memory


  • Potentially unlimited capacity
  • Can be active or passive
• Consolidation


  Transferring of information from short to longer-term memory
• Retrograde Amnesia


  Loss of memory for events just prior to an injury

  
• Anterograde Amnesia


  An inability to form new memories after an injury

  
• Henry Molaison (H.M.)


  Had intractable epilepsy, seizures originating bilaterally in medial temporal lobes