Replay of factorized temporal journey

Time is a fundamental dimension of episodic memory, structuring the sequence of events that form our experiences. While replay of spatial paths and item sequences has been extensively studied in recent years, the role of temporal replay remains unclear. Here, we asked whether the brain replays time in a factorized manner. Our results revealed content-independent temporal trajectories that were replayed both during memory retrieval and post-retrieval rest, with on-task replay supporting immediate recall and off-task replay contributing to the consolidation of weaker memories. Furthermore, the alignment between cortical replay and sharp wave ripples in the hippocampal reveals that hippocampal-cortical replay may serve as a unifying mechanism for organizing "where", "what", and "when" of episodic memory.