Hippocampal neuron firing is variable across laps in a linear track task

[Speaker] Saichiro Yagi:1
[Co-author] Hideyoshi Igata:1, Yu Shikano:1, Yuki Aoki:1, Takuya Sasaki:1,2, Yuji Ikegaya:1
1:Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Japan, 2:Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Japan

Hippocampal cells increase their firing frequency when an animal is located in given restricted areas of an environment, termed place fields. In the majority of studies, firing patterns of 'place cell' have been characterized based on the spatial distribution of firing rates averaged over the entire sessions; however a place cell emits variable numbers of action potentials even when the animal visits the same place field along the nearly identical pass. We hypothesized that such variable spatial firing of individual place cells is associated with the ensemble-level time-varying activity of neuronal populations. To address this idea, we monitored the spiking patterns of hippocampal pyramidal cells while rats performed a linear track task with a fixed goal. Both firing rates of place cells in the track and synchronous reactivation patterns of neuronal ensembles during consummatory periods varied across laps. A linear regression analysis demonstrated that the lap-by-lap changes in spiking patterns of neuronal populations could predict the activity level of a place cell in subsequent running. The results suggest that the pattern of place cell firing is not simply determined by instantaneous inputs from the external environments but is also subject to the internal states of neuronal populations including place cells and others.
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