Hippocampal-prefrontal interactions during theta oscillations are the most well-established, with multiple studies demonstrating co-ordination of activity of neurons in the two regions during periods of high theta phase coherence [25–27,40,41] (also reviewed elsewhere [21,28]). Theta oscillations are prominent in the hippocampus during active exploration associated with place cell activity. Prefrontal neurons exhibit phase-locking to hippocampal theta, and synchronization of the theta rhythm (phase coherence) between the two regions is elevated specifically during periods of memory-guided decision making as compared to passive exploration [25–27,41] (Figure 2). Enhanced theta coherence is also seen during performance of correct vs. incorrect trials [26,27,41], and activity of theta phase-locked prefrontal neurons is correlated to task representations [27,40]. Elevated spiking correlations during these periods of high theta coherence [26] and the relationship with correct memory performance [27] indicates that ensemble spiking activity in the two regions is coordinated to support the exchange of mnemonic information.
