Scalable representation of time in the hippocampus

Hippocampal time cells encode specific moments of temporally organized experiences that may support hippocampal functions for episodic memory. However, little is known about the reorganization of the temporal representation of time cells during changes in temporal structures of episodes. We investigated CA1 neuronal activity during temporal bisection tasks, in which the sets of time intervals to be discriminated were designed to be extended or contracted across the blocks of trials. Assemblies of neurons encoded elapsed time during the interval, and the representation was scaled when the set of interval times was varied. Theta phase precession and theta sequences of time cells were also scalable, and the fine temporal relationships were preserved between pairs in theta cycles. Moreover, theta sequences reflected the rats' decisions on the basis of their time estimation. These findings demonstrate that scalable features of time cells may support the capability of flexible temporal representation for memory formation.

Automated summary

The study shows that neuronal assemblies encode elapsed time in time cells, displaying scalable features in temporal bisection tasks. Additionally, these neuronal assemblies can adjust according to different sets of time intervals, reflecting rats' time estimation, demonstrating that time cells may support the capability of flexible temporal representation for memory formation.