Evidence for a sub-circuit in medial entorhinal cortex representing elapsed time during immobility

Abstract

The medial entorhinal cortex (MEC) is known to contain spatial encoding neurons that likely contribute to encoding spatial aspects of episodic memories. However, little is known about the role MEC plays in encoding temporal aspects of episodic memories, particularly during immobility. Here, using a virtual “Door-Stop” task for mice, we show MEC contains a representation of elapsed time during immobility, with individual time encoding neurons activated at a specific moment during the immobile interval. This representation consisted of a sequential activation of time encoding neurons and displayed variations in progression speed that correlated with variations in mouse timing behavior. Time and spatial encoding neurons were preferentially active during immobile and locomotion periods, respectively, were anatomically clustered with respect to each other and preferentially encoded the same variable across tasks or environments. These results suggest the existence of largely non-overlapping sub-circuits in MEC encoding time during immobility or space during locomotion.