reward circuits and drug addiction

The Neural Basis of Associative Learning

• Aversive (Fear) and Appetitive Associative Learning

– Contributions of the Amygdala and Striatum

– Instrumental learning and conditioned reinforcers

amygdala - learning to be afraid of potentially harmful things

  • helps from associations between emotional responses and specific memories of stimuli that are stored somewhere else in the brain

  • cues associated with reward influence our behaviour (conditioned place preference, conditioned reinforcement)

associative learning - learning that involves relations between two stimuli

Pavlovian conditioning - classical conditioning - initially neutral stimulus predicts an event

4 main elements

  • Unconditioned stimulus: biologically significant event (ex. food)

  • unconditioned response - normal response to US (salivating to food)

  • conditioned stimulus - initially neutral, but it now predicts the significant event (bell predicts food)

  • conditioned response - body’s response to CS alone (salivating to bell)

5 key points

  • CS MUST predict US (bell predicts food)

  • organism cant control delivery of cs and us

  • cr is also uncontrollable

  • humans - not conscious of CR

  • long lasting - can be extinguished but reinstated quickly

hippocampus = spatial learning

amygdala = fear and appetitive conditioning

striatum = instrumental learning

nmda and ampa

ltp - net effect of changes is to enhance sensitivity of synapse to released glutamate

after depolarization through AMPA - NMDA lets ca2+ ions in which activate CamK, PKC and TK

  • caMK sends AMPA receptors to membrane

  • PKC and TK activate CREB

  • CREB lead to formation of retrograde messenger (goes to presynaptic terminal to promote more transmitter release)

executive function - high-level cognitive processes that control and organize lower-level processes

  • direct short-term actions while keeping long-term goals in mind

  • selecting and monitoring behaviours that aid in attainment of chosen goals

dorsolateral pfc - executive control, working memory

  • dlpfc similar to rats medial pfc