Hippocampal cell assemblies are speed controlled oscillators

During exploratory behavior and REM sleep hippocampal network is engaged in a prominent theta rhythm. Surprisingly, hippocampal pyramidal cells (place cells) oscillate at frequencies faster than that of the local field potential. We show that at faster running speeds place cells are active for fewer theta cycles but oscillate at a higher frequency. This results in invariance of the phase-space correlation of place cell firing despite of large variability in running speed, a well known phase precession phenomenon. A subset of interneurons also show transient acceleration of their oscillation relative to the mean field and contribute to the formation of coherent cell assemblies. This framework allows us to also extend the analysis to non-spatial behavior, such as REM-sleep. We discuss possible mechanisms of this phenomenon.

Last Modified: Jan 15 200