Increases in long-range theta phase synchrony support the hypothesis that episodic memory in humans relies on theta oscillations to coordinate cellular activity across disparate regions. But these findings also raise an important question: Why are there many reports of increased memory-related theta phase synchrony using intracranial measures, even as almost every intracranial study reports predominantly decreased theta power? If theta oscillations coordinate activity across distant brain regions, we would expect changes in local power and inter-regional synchronization to occur in tandem, not in opposite directions.
