Pyramidal neurons in region CA1 of the rat hippocampus display
place-specific firing as the animal explores a spatial environment,
leading to the name "place cells". During REM sleep following
exploration, place cells reactivate their firing in the same temporal
patterns and on the same time scale as occurred during waking. It is
hypothesized that this replay firing plays a role in the learning of the
spatial memory or map constituted by place cell firing sequences. Poe
et al (Brain Res 855:176-180, 2000) observed a change in the pattern of
place cell reactivation firing in REM sleep that occurred over several
days as the rat learned a new spatial environment. Specifically, the
firing pattern changed from one that supported synaptic strengthening
(long-term potentiation and learning) during the first 2 days to a
pattern that supported synaptic weakening (depotentiation and
forgetting) after the third day of exposure to the new environment. In
simulation studies using a realistic CA1 pyramidal neuron model, we
investigated neural mechanisms that account for this shift in
reactivation firing pattern. In this talk, we describe our model of the
neuronal components involved in place cell firing and our modeling
results that suggest a novel pattern of synaptic plasticity that occurs
during learning and memory consolidation.
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