Non-uniform excitability of hippocampal neurons affords weak predictability of future immediate-early gene expression patterns

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Demchuk, Aubrey M.
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Lethbridge, Alta. : University of Lethbridge, Dept. of Neuroscience
Early immediate-early gene (IEG) studies and electrophysiological data support the “uniform random sample with replacement” (URSWR) model for the orthogonalization of memory representations in the rodent hippocampus. This model is challenged, however, by the observed “preplay” of place cell firing sequences and recent IEG studies that fail to demonstrate the proportionate increase in neuron recruitment predicted to accompany multiple environments. Thus, the purpose of this study was to assess preplay at the molecular level. Utilizing Arc/Homer1a fluorescent in situ hybridization, this study compared patterns of rat neural activity during rest in a familiar environment and during the subsequent exploration of a novel environment. The observed overlap between IEG expression patterns was statistically equivalent to that expected by the URSWR model in both CA1 and CA3 but became significantly higher when analysis was restricted to presumably highly active cells, effectively uniting both the URSWR and preselection models of hippocampal pattern separation.
spatial memory , pattern separation , preplay , Arc , Homer1a , hippocampus