Ultraslow oscillations as a temporal scaffold for coordinating episodic memories

Abstract

Abstract The entorhinal–hippocampal circuit plays a central role in episodic memory, yet the contribution of the medial entorhinal cortex (MEC) ultraslow (< 0.01 Hz) oscillation remains poorly understood. Here, we develop a biologically inspired computational oscillation-coordinated replay model integrating MEC-like ultraslow oscillations with entorhinal grid–hippocampal place cell interactions and injected replay-like sequential activity. In the model, replay-like events were probabilistically triggered and temporally aligned to an imposed ultraslow oscillatory scaffold. We compared this condition to a baseline lacking both oscillatory modulation and replay-like structure. Under these conditions, recall accuracy and coding overlap were higher when replay-like dynamics were coordinated by the oscillatory scaffold. The present results demonstrate that oscillatory structure can enhance the temporal organization and effectiveness of replay-like dynamics. These findings provide a proof-of-concept framework for understanding how ultraslow fluctuations may contribute to memory processes by coordinating, rather than generating, replay activity, and enabling testable predictions for models in which replay emerges endogenously.