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Unformatted text preview: a good place • • Learning the location of a platform hidden under opaque water requires intact
hippocampus. The spatial information come from sensory cues outside of the maze
and from self-motion
Drugs that block synaptic plasticity (long-term potentiation mediated by NMDA
channels) impair behavioral learning. Long Term Potentiation (LTP)
and NMDA Receptor Gene Knockout NMDA receptor is responsible for the associative
LTP in CA3 to CA1 synapses. The synaptic
strength, as measured by the excitatory
postsynaptic potential (EPSP), can stay increased
over 1 hour after only 1 second of strong stimuli.
Knockout mice that lack one subunit of NMDA
receptor in CA1 (dark band in the slice above)
have defective LTP (left), unstable place fields, and
cannot learn Morris water maze. Place cell plasticity: Asymmetric expansion effect
explained by Hebbian learning
last lap 1st lap Hippocampal place fields
on a track with a rat running
continuously back and forth Firing rate (recorded neuron)
CA1 place field expands and shifts backwards.
Red curve: 1st lap
Blue curve: last lap
(Mehta) Review: supervised learning in a perceptron
Output: y = ∑ wi xi
input pattern: x1, x2, x3, …
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This document was uploaded on 02/28/2014 for the course BME 580.402 at Johns Hopkins.
- Spring '14