It has become increasingly clear that we must transition from approaching brain regions as modular entities, and instead consider the influence and role of joint inter-regional activity, particularly in the generation of complex behaviors. As we described here, the role of the hippocampus in learning and memory is well-established, but the mechanisms through which it communicates with other regions to engender multi-region mnemonic representations and enable memory-guided behavior is poorly understood. It appears likely that bidirectional flow of memory related information between the hippocampus and PFC supports memory formation, contextual memory retrieval, and memory-guided decisions. The ubiquitous presence of ensemble network activity patterns in these regions and the dynamic transitions between these states during behavior suggests that a mechanism where neural populations switch on and off their activity for sub serving certain functions is too simplistic. Understanding the role of prominent physiological patterns in these regions can reveal organizational principles through which the brain utilizes specific activity patterns for local information processing in the context of long-range communication across regions. Multiple experimental and analytical approaches must be combined for this
