Time and the hippocampus

Abstract

Episodic memory is defined by the temporal organization of events in specific experiences. The hippocampus plays an essential role in episodic memory, suggesting that studies on temporal processing by the hippocampus might offer insights in the mechanisms of episodic memory. Here, we review reports on the effects of hippocampal damage in humans and animals and physiological studies using brain imaging in humans and single neuron recordings in animals. These studies provide converging and compelling evidence that the hippocampus is critical for the temporal organization of memories in humans and animals, including when spatial cues are irrelevant. Furthermore, the hippocampus in engaged in humans associated with temporal processing of memories, and hippocampal neuronal networks in animals and humans represent the temporal organization of experiences and disambiguate overlapping temporally extended experiences. In particular, hippocampal time cells fire at particular moments during temporally structured experiences, much as hippocampal place cells fire associated with particular locations in spatially organized experiences. Comparisons of firing properties of hippocampal neurons across species and behavioral situations suggest that the hippocampus provides a temporal and spatial scaffolding that organizes events to compose episodic memories.