Integration and competition between space and time in the hippocampus.

Episodic memory is organized in both spatial and temporal contexts. The hippocampus is crucial for episodic memory and has been demonstrated to encode spatial and temporal information. However, how the representations of space and time interact in the hippocampal memory system is still unclear. Here, we recorded the activity of hippocampal CA1 neurons in mice in a variety of one-dimensional navigation tasks while systematically varying the speed of the animals. For all tasks, we found neurons simultaneously represented space and elapsed time. There was a negative correlation between the preferred space and lap duration, e.g., the preferred spatial position shifted more toward the origin when the lap duration became longer. A similar relationship between the preferred time and traveled distance was also observed. The results strongly suggest a competitive and integrated representation of space-time by single hippocampal neurons, which may provide the neural basis for spatiotemporal contexts. [Display omitted] • Hippocampal CA1 single neurons concurrently represent space and time • The preferred location of some cells shifts with lap duration • The preferred time of some cells shifts with lap distance • There is a competitive interaction between space and time To study how the representation of space and time interact in the episodic memory system, Chen et al. showed that hippocampal CA1 neurons simultaneously represented space and elapsed time, and the neuronal firing reflected a trade-off or competition between space and time by shifting their fields in space or time. [ABSTRACT FROM AUTHOR]