Bridges, not walls: the hippocampus builds narrative memories across distant events

Recent studies have suggested that activity in the hippocampus is increased during divisions between events in memory, or "event boundaries." Although hippocampal activity at event boundaries may play a role in segregating adjacent events, it might also serve a counterintuitive purpose: to bridge the divide between distant events that form a larger narrative. We used functional neuroimaging to investigate whether patterns of hippocampal activity at event boundaries support the integration of distant events in memory, when these events can form a larger narrative. During encoding of fictional stories, boundary-evoked hippocampal activity patterns were more similar between distant events that formed one coherent narrative, than between distant events from unrelated narratives. Twenty-four hours later, detailed recall of coherent narrative events was supported by the reinstatement of boundary-evoked hippocampal activity from encoding. These findings reveal a key function of the hippocampus: the dynamic integration of events into a narrative structure for memory.