Learned fear and reaction to novel stimuli: behavioral and ...
Fear conditioning e.g., Electric shock associated with specific stimuli.
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Transcript of Fear conditioning e.g., Electric shock associated with specific stimuli.
Fear conditioning…
e.g., Electric shock associated with specific stimuli
SCR: Skin Conductance Response (sweat)
Fear-relevant: e.g., snakeFear-irrelevant: e.g., butterfly
SCR: Skin Conductance Response (sweat)
Fear-relevant: e.g., snakeFear-irrelevant: e.g., butterfly
SCR: Skin Conductance Response (sweat)
SCR: Skin Conductance Response (sweat)
SCR: Skin Conductance Response (sweat)
Same RaceDifferent Race
• 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
Operant conditioning
Biological needs
Several hours have passed since last meal
Find food, eat it
Drive is reduced (reinforcement)
The drive reduction hypothesis
Increased drive (hunger)
Increased exploratory activity
Biological needs
Several hours have passed since last meal
Increased drive (hunger)
Increased exploratory activity
Find food, eat it
Drive is reduced (reinforcement)
The drive reduction hypothesis
For instance, rats learning to work for food
Skinner Box
For instance, rats learning to work for food
Response to central hole= a way to obtain food
Phase One
A new experiment…
Response to central hole= a way to obtain food
Phase One
A new experiment…
Better deal to the right> Will rats figure it out?
Phase Two
Better deal to the right> Will rats figure it out?
Better deal to the right> Will rats figure it out?
Yes, in a couple of days
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 releasechanges 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 transmissionfollowing activation of a synapse by intense high-
frequencystimulation 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
• Declarative memory – Facts (who is…, what is…)– Events (when did you…)
• Non-declarative memory– Procedures (how do you…)– Conditioning (automatic responses)
•Musculature •Emotional
Medial temporal lobe
Hippocampus
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
Medial temporal lobe
Hippocampus
Striatum
Cerebellum
Amygdala
Types of memory
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”)