Transcript Learning 2
Fear conditioning… e.g., Electric shock associated with specific stimuli SCR: Skin Conductance Response (sweat) Fear-relevant: e.g., snake Fear-irrelevant: e.g., butterfly SCR: Skin Conductance Response (sweat) Fear-relevant: e.g., snake Fear-irrelevant: e.g., butterfly SCR: Skin Conductance Response (sweat) SCR: Skin Conductance Response (sweat) Same Race Different Race SCR: Skin Conductance Response (sweat) Operant conditioning • Operant Conditioning: learning when an individual’s response is followed by a reinforcement or punishment – Reinforcement: an event that increases the future probability of the response that produced it • Positive reinforcement: Reward • Negative reinforcement: Escape from punishment – Punishment: an event that suppresses the future probability of the response that produced it Biological needs The drive reduction hypothesis Several hours have passed since last meal Increased drive (hunger) Increased exploratory activity Drive is reduced (reinforcement) Find food, eat it Biological needs The drive reduction hypothesis Several hours have passed since last meal Increased drive (hunger) Increased exploratory activity Drive is reduced (reinforcement) Find food, eat it For instance, rats learning to work for food For instance, rats learning to work for food Skinner Box A new experiment… Phase One Response to central hole = a way to obtain food A new experiment… Phase One Response to central hole = a way to obtain food Phase Two Better deal to the right > Will rats figure it out? 1.000 0.900 Peripheral Preference Rate 0.800 0.700 0.600 0.500 0.400 0.300 0.200 0.100 0.000 day 1 day 2 Better deal to the right > Will rats figure it out? day 3 day 4 day 5 1.000 Yes, in a couple of days 0.900 Peripheral Preference Rate 0.800 0.700 0.600 0.500 0.400 0.300 0.200 0.100 0.000 day 1 day 2 Better deal to the right > Will rats figure it out? day 3 day 4 day 5 Concurrent changes in neural functioning • growth of new neurons • growth of new synapses • increase or decrease in transmitter release • increase or decrease in sensitivity to transmitter release changes in concentration of receptors Long Term Potentiation • The most widely studied neuroplastic phenomena of the mammalian nervous system • Considered a fundamental mechanism underlying learning and memory in mammals. What is Long Term Potentiation? Enduring facilitation of synaptic transmission following activation of a synapse by intense high-frequency stimulation of pre-synaptic neurons… or Changes in the postsynaptic neuron resulting in the strengthening of synaptic transmission. The key event is the co-occurrence of the pre and post synaptic neurons. Neurons that fire together wire together while neurons that are out of sync lose their link. Most commonly studied in neurons from the hippocampus Biochemical Mechanisms of LTP in Hippocampus • AMPA and NMDA receptors are involved in LTP – glutamate receptors that open channels in postsynaptic neurons to let in one or more kinds of ions (ionotropic) • AMPA receptors: glutamate opens sodium channels • NMDA receptors: normally blocked by magnesium but respond to glutamate when the neuron is depolarized by AMPA receptors – calcium enters and activates protein CaMKII, which is necessary for LTP, and sets several processes in motion: • structure of AMPA receptors change, becoming more responsive to glutamate • some NMDA receptors change to AMPA receptors and increase their responsiveness to glutamate • dendrites may build more AMPA receptors and make more branches • Once established, LTP no longer depends on NMDA synapses LTP and Behavior • Research shows – abnormal NMDA receptors impair learning – more than normal NMDA receptors enhances learning – drugs that block LTP block learning while drugs that facilitate LTP facilitate learning – a lack of AMPA receptors creates deficits in LTP and memory Types of memory • Declarative memory – Facts (who is…, what is…) – Events (when did you…) • Non-declarative memory – Procedures (how do you…) – Conditioning (automatic responses) •Musculature •Emotional Types of memory • Declarative memory – Facts (who is…, what is…) – Events (when did you…) Medial temporal lobe Hippocampus • Non-declarative memory – Procedures (how do you…) – Conditioning (automatic responses) •Musculature •Emotional Types of memory • Declarative memory Medial temporal lobe – Facts (who is…, what is…) – Events (when did you…) Hippocampus • Non-declarative memory – Procedures (how do you…) Striatum – Conditioning (automatic responses) •Musculature Cerebellum •Emotional Amygdala More types of memory… • Long-term memory – Questions about encoding, retrieving – Medial temporal lobe (“store”) • Short-term memory – Working memory – (Consciousness, attention) – Dorsolateral frontal cortex (“operator”)