Delta-range coupling between prefrontal cortex and hippocampus supported by respiratory rhythmic input from the olfactory bulb in freely behaving rats

Abstract

Respiratory rhythm (RR) during sniffing is known to couple with hippocampal theta rhythm. However, outside of the short sniffing bouts, a more stable ~2Hz RR was recently shown to rhythmically modulate non-olfactory cognitive processes, as well. The underlying RR coupling with wide-spread forebrain activity was confirmed using advanced techniques, including current source density and phase modulation of local gamma activity, creating solid premise for investigating how higher networks use this mechanism in their communication. Here we show essential differences in the way prefrontal cortex (PFC) and hippocampus (HC) processes the RR signal from the olfactory bulb (OB) allowing dynamic PFC-HC coupling utilizing this input. We found stable OB-PFC coherence in waking contrasting low but highly variable OB-HC coherence. PFC-HC coupling however primarily correlated with the latter, indicating that HC access to the PFC output readily segmented and shaped by RR in the delta range is dynamically regulated by the responsiveness of HC to the common rhythmic drive.