Abstract
Our everyday experience shapes how we represent the structure of the world. Retrieval of these experiences from memory is fundamental for informing our future decisions. To uncover the fine-grained neurophysiological mechanisms that support such retrieval we studied participants who first experienced unique multi-component episodes, and subsequently completed cued memory retrieval of these whilst undergoing magnetoencephalography (MEG). Successful retrieval was supported by sequential replay of episodes, with a temporal compression factor greater than 60. This sequential replay was stronger in those participants with weaker overall memories. Replay direction, forward or backward, was dependent on whether a participant’s goal was to retrieve elements of an episode that followed, or preceded, a retrieval cue. Our results demonstrate that memory-based decisions are supported by a rapid replay mechanism that flexibly shifts in direction.