Abstract
Hippocampal ripples are highly synchronized neuronal population patterns reactivating past waking experiences in the offline brain. Whether the level, structure, and content of ripple-nested activity are consistent across consecutive events or are tuned in each event remains unclear. By profiling individual ripples using laminar currents in the mouse hippocampus during sleep/rest, we identified ripples in stratum pyramidale that feature current sinks in stratum radiatum (Rad(sink)) versus stratum lacunosum-moleculare (LM(sink)). These two ripple profiles recruit neurons differently. Rad(sink) ripples integrate recent motifs of waking coactivity, combining superficial and deep CA1 principal cells into denser, higher-dimensional patterns that undergo hour-long stable reactivation. By contrast, LM(sink) ripples contain core motifs of prior coactivity, engaging deep cells in sparser, lower-dimensional patterns that undergo a reactivation drift to gradually update their pre-existing content for recent wakefulness. We propose that ripple-by-ripple diversity supports parallel reactivation channels for integrating recent wakefulness while updating prior representations.