Neural representations of time and space underlying episodic memory
To perceive and form memories of everyday experiences, animals and humans must accurately represent time intervals, even during periods of many seconds of immobility when external sensory cues may not change in a temporally informative manner. Such a capability may be realized by activity patterns across brain circuits that can form an internally generated representation of elapsed time. In this seminar, I will present results demonstrating that the medial entorhinal cortex (MEC) contains a previously unknown representation of elapsed time during immobile periods of virtual navigation-based tasks. Furthermore, I will show that time encoding cells and (previously described) spatial encoding cells belonged to largely non-overlapping neuronal populations, which were anatomically clustered in MEC and, importantly, were much more likely than chance to encode the same variable (time or space) when animals were switched to different tasks or environments. Together, these results suggest that MEC contains a neuronal circuit specializing in encoding elapsed time during immobility, which is distinct from the circuit specializing in encoding space during locomotion.