Theta dominates cross-frequency coupling in hippocampal-medial entorhinal circuit during awake-behavior in rats

Hippocampal theta and gamma rhythms are hypothesized to play a role in the physiology of higher cognition. Prior research has reported that an offset in theta cycles between the entorhinal cortex, CA3, and CA1 regions promotes independence of population activity across the hippocampus. In line with this idea, it has recently been observed that CA1 pyramidal cells can establish and maintain coordinated place cell activity intrinsically, with minimal reliance on afferent input. Counter to these observations is the contemporary hypothesis that CA1 neuron activity is driven by a gamma oscillation arising from the medial entorhinal cortex (MEC) that relays information by providing precisely timed synchrony between MEC and CA1. Reinvestigating this in rats during appetitive track running, we found that theta is the dominant frequency of cross-frequency coupling between the MEC and hippocampus, with hippocampal gamma largely independent of entorhinal gamma.Funding provided by: National Institutes of HealthCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000002Award Number: Funding provided by: Evelyn F. McKnight Brain Research FoundationCrossref Funder Registry ID: http://dx.doi.org/10.13039/100007049Award Number: Funding provided by: National Institute on AgingCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000049Award Number: AG055544Funding provided by: National Institute of Mental HealthCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000025Award Number: MH10954