Theta rhythms occur prominently in the hippocampus and entorhinal cortex during active behaviors [1] and play a key role in memory processing [2,3]. Within each hippocampal theta cycle, bursts of gamma oscillations emerge [4,5], raising the possibility that such theta-gamma interactions are a critical component of mnemonic operations. Theta-nested gamma oscillations may allow the hippocampal-entorhinal network to temporally organize sequences of events within each theta cycle [6–9].
