Rhythmic oscillations at distinct frequencies, seen in the electroencephalogram or local field potential (LFP) activity, are an integral feature of neural activity in many brain regions. These network activity patterns (“network patterns”) reflect organized activity of underlying neural ensembles, and are thought to support both local information processing and coordination between brain regions during cognition in diverse model systems [10–17]. In particular, phase coherence of oscillations across regions has been proposed to be a mechanism for coordination. However, current evidence remains primarily phenomenological, and a causal demonstration that coherence of network rhythms plays a specific role in cognitive processing is still lacking. Multiple network patterns have been ascribed roles in organizing local processing in the hippocampal network during behavior, including slow theta oscillations (6–12 Hz), beta (15–20 Hz) and gamma rhythms (40–100 Hz), and fast network oscillations, in particular sharp-wave ripples (SWRs, 150–250 Hz) [7,13,18–20]. Similarly, multiple rhythms are also implicated in information processing in PFC [11,14,21–24]. In the past decade, focus on hippocampal-prefrontal interactions has been primarily in the context of theta oscillations [21,25–28], but it is now increasingly clear that other network patterns also mediate interactions among these regions [7,29–31].
