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weak

weak. strong. Recall: Hebb’s rule. “Successful use” Need both Pre- and Post-synaptic activity. Weak alone: only presynaptic. Strong alone: only postsynaptic (at the “weak input synapse). Both weak and strong: both pre and post. weak. CS. US. strong. CS. US

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weak

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  1. weak strong Recall: Hebb’s rule “Successful use” Need both Pre- and Post-synaptic activity Weak alone: only presynaptic Strong alone: only postsynaptic (at the “weak input synapse) Both weak and strong: both pre and post

  2. weak CS US strong CS US center R US Analogy to Pavlovian Conditioning CS? US?

  3. + + + Action Potential + + T T T T T T T T T T T Vesicles containing Neurotransmitter What Changes? Receptor T Possible changes: More NT More Receptors Other axon dendrite Synaptic cleft or gap

  4. How does it Change? Na+ Na+ Action Potential Na+ T T T T T T T T T T T Na+ Ca++ Na+ Mg++ Ca++ Ca++ Ca++ Non-NMDA Receptor T NMDA Receptor axon Na = sodium Ca = calcium Mg = magnesium T Vesicles containing Neurotransmitter (Glutamate) Mg++ Stuff happens

  5. NMDA Non- NMDA NMDA Non- NMDA Hebb’s rule: Need both release of neurotransmitter (presynaptic activity) and depolarization (postsynaptic activity): Then Ca++ can enter through NMDA receptor

  6. Convergence of CS and US

  7. Fear conditioning: Role of Amygdala e.g., Tone—shock Freezing, etc. Virtually all Fear CRs are eliminated by Amygdala lesion

  8. LTP occurs during conditioning Remember: Learning-Performance distinction Inactivation experiments. What if we prevent LTP?

  9. Na+ Na+ Action Potential Na+ T T T T T T T T T T T Non-NMDA Receptor T NMDA Receptor axon Na = sodium Ca = calcium Mg = magnesium Vesicles containing Neurotransmitter (Glutamate) Antagonist Mg++ Interfering with LTP during training (like inactivation expts.), disrupts conditioning (sometimes).

  10. Summary: Evidence for role of amygdala (and LTP) in fear conditioning Amygdala offers a site of convergence of CS and US Virtually all Fear CRs are eliminated by Amygdala lesion LTP occurs in Amygdala Interfering with LTP in Amygdala disrupts fear conditioning (sometimes)

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