No Slide Title

							            LTP - Long-Term Potentiation (Lomo,1966)
Learning » experience (conditioning, thinking) changes the CNS
(permanently?) and therefore behavior.
Hebb Rule : when synapse is repeatedly active as the post-synaptic
neuron fires, this synapse becomes strengthened.
“Airpuff”           strong synapse       CC or Associative LTP


                                         “Blink”




“Tone”              weak synapse         post-synaptic neuron
Pinel
Text
NMDA - Receptor (N-methyl-D-Aspartate)
Glutamate
(1)Transmitter + (2)voltage gated receptor


Glutamate     Post-synaptic depolarization » ejects magnesium
              block from calcium channel » glutamate opens
              channel » calcium enters post-synaptic cell.
» Ca++ » enzymes: protein kinases (3?) » change non-NMDA
(AMPA?) glutamate receptors; enzymes also produce nitric
oxide (NO), a retrograde messenger (back to presynaptic
terminal) releasing more glutamate (?)


See diagram
Structural Changes?
A) more post-synaptic receptors (AMPA, Glutamate)
B) more transmitter (Glutamate) release
C) growth of more terminal buttons (pre-synaptic)
D) thicker dendritic spines » easier to depolarize (e.g., EPSP)
Long-term Depression (LTD): “undo LTP”
       Low-frequency stimulation (< 10 Hz)
       Extinction?
NMDA receptor blocker - AP5 (amino phosphono valeric acid)
       **AP5 interferes with learning
Reinforcement: DA & Enkephalins
                 (DA antagonists, Naloxone block LTP)
Review of cascade in LTP
1. Post-synaptic depolarization » magnesium blocked removed
2. Glutamate-binding » Ca ++ enters cell
3. Ca++ » protein kinases
4. Functional and structural changes :
A) increases non-NMDA receptors (AMPA)
B) changes shape of spines


C)   NO » Glutamate release increased
D)   sprouting buttons increased


A & B are post-synaptic and C & D are pre-synaptic
                       4D



              1

     2


4B
     3
         4A

                  4C
                 Associative LTP
CER » amygdala (LeDoux, 2000)


      shock       “strong”


                                Response (CER)
                                a) autonomic (heart)
                                b) skeletal (freeze)
      tone        “weak”