Hippocampus whispering in deep sleep to prefrontal cortex--for good memories?

Enduring episodic memories are thought to be formed in a dialog between hippocampus and neocortex promoting the redistribution of newly encoded memories from hippocampal to neocortical stores. In this issue of Neuron, Wierzynski et al. report that during slow wave sleep (SWS), driven by hippocampal sharp wave-ripple bursts, cells in prefrontal cortex fire consistently within 100 ms after hippocampal cells, i.e., a time window that allows for synaptic plastic changes in the neocortical cells. These observations corroborate evidence for a hippocampo-to-neocortical transfer of memories taking place during SWS.