Nested sequences of hippocampal assemblies during behavior support subsequent sleep replay

During exploration, hippocampal place cells activate one after the other forming sequences that represent the ongoing trajectory at the behavioral timescale. During subsequent slow wave sleep, the same sequences are endogenously replayed at a highly accelerated pace, contributing to memory consolidation. How is this sequential organization maintained across two different time scales, expressed at disjoint moments in time and during different brain states? We show that this requires faster sequences at the theta (~150 ms) time scale, nested within the slow, behavioral time scale sequences.

C. Drieu, R. Todorova, M. Zugaro (2018). Science 362(6415):675-679.