The medial entorhinal cortex (MEC) hosts many of the brain’s circuit elements for spatial navigation and episodic memory, operations that require neural activity to be organized across long durations of experience. We have previously found that when mice were head-fixed on a wheel and ran at their own pace in darkness, entorhinal cells organized their activity into ultraslow oscillations (frequency < 0.1 Hz) that manifested as periodic sequences of activity in the neural population (Gonzalo Cogno et al., 2024). It remains unknown, however, whether the sequences also occur during more naturalistic behaviours, for example while mice run in an open field arena, or during sleep. In this presentation I will show that in free foraging conditions, MEC neuronal activity can organize into sequences. We found much variability in the duration of the sequences, yet all sequences were in the tens of seconds time scale. Moreover, we found found that within a session, the MEC always generates the same sequence ordering, and this ordering recurs over time. The sequences, however, are now characterized by resettings and interruptions. By developing a computational model, we investigate the conditions under which the sequences reset. In addition, we found that that ultraslow periodic activity persisted during sleep, particularly during slow wave sleep. However, this ultraslow activity manifested as ultraslow oscillations that were highly synchronous across the population, and not as sequences. The oscillations also manifest in the hippocampus, and are highly synchronized with those in the MEC. Our results point to the existence of internal dynamics that unfold at ultraslow time scales, and that are modulated by sensory information and cognitive demands.