Remembering episodes: a selective role for the hippocampus during retrieval

Some memories are linked to a specific time and place, allowing one to re-e xperience the original event, whereas others are accompanied only by a feel ing of familiarity. To uncover the distinct neural bases for these two type s of memory, we measured brain activity during memory retrieval using event -related functional magnetic resonance imaging. We show that activity in th e hippocampus increased only when retrieval was accompanied by conscious re collection of the learning episode. Hippocampal activity did not increase f or items recognized based on familiarity or for unrecognized items. These r esults indicate that the hippocampus selectively supports the retrieval of episodic memories.