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NJIT Mathematical Biology Seminar

Tuesday, November 28, 2006, 4:00pm
Cullimore Hall 611
New Jersey Institute of Technology

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Hippocampal place cells are speed-controlled oscillators

Caroline Geisler

Center for Molecular and Behavioral Neuroscience
Rutgers University

The phase of spikes of hippocampal pyramidal cells relative to the local field theta oscillation shifts forward ("phase precession") over a full theta cycle as the animal crosses the cell's receptive field ("place field"). The linear relationship between the phase of the spikes and the travel distance within the place field is independent of the animal's running speed. This invariance of the phase-distance relationship is likely to be important for coordinated activity of hippocampal cells and space coding, yet the mechanism responsible for it is not known. Here we show that at faster running speeds place cells are active for fewer theta cycles but oscillate at a higher frequency and emit more spikes per cycle. As a result, the phase shift of spikes from cycle to cycle (i.e., temporal precession slope) is faster, yet spatial phase precession stays unchanged. Interneurons also show transient phase precession and contribute to the formation of coherently precessing assemblies. We hypothesize that the speed-correlated acceleration of place cell oscillation is responsible for the phase-distance invariance of hippocampal place cells.