Hippocampal Place Cells Couple to Three Different Gamma Oscillations during Place Field Traversal

Abstract

Three distinct gamma oscillations, generated in different CA1 layers, occur at different phases of concurrent theta oscillation. In parallel, firing of place cells displays phase advancement over successive cycles of theta oscillations while an animal passes through the place field. Is the theta-phase-precessing output of place cells shaped by distinct gamma oscillations along different theta phases during place field traversal? We simultaneously recorded firing of place cells and three layer-specific gamma oscillations using current-source-density analysis of multi-site field potential measurements in mice. We show that spike timing of place cells can tune to all three gamma oscillations, but phase coupling to the mid-frequency gamma oscillation conveyed from the entorhinal cortex was restricted to leaving a place field. A subset of place cells coupled to two different gamma oscillations even during single-place field traversals. Thus, an individual CA1 place cell can combine and relay information from multiple gamma networks while the animal crosses the place field.