Both the prefrontal cortex and the hippocampus are crucial for memory encoding and recall. However, it remains unclear how these brain regions communicate to exchange information. Recent findings using simultaneous recordings from the hippocampus and prefrontal cortex of the behaving rat have demonstrated that prefrontal cells' firing is phase-locked to the hippocampal theta rhythm. This suggests that phase synchronization clocked by the theta rhythm could be crucial for the communication between hippocampal and prefrontal regions.