A CLAUSTRAL PATHWAY LINKS HIPPOCAMPAL AND CORTICAL RHYTHMS TO SUPPORT SLEEP-DEPENDENT MEMORY CONSOLIDATION

Sleep consolidates recent experience by coordinating hippocampal–cortical activity, yet how distant structures achieve temporally ordered communication is unclear. We identify a claustral population projecting to the subicular complex (CLAsc) that provides direct access to hippocampal output territories while maintaining dense cortical collaterals. Using dual-viral tracing, fiber photometry, multi-site electrophysiology, and optogenetic activation during post-learning slow-wave sleep (SWS), we show that CLAsc neurons are preferentially active during synchronized cortical states. CLAsc stimulation enhances memory and evokes a stereotyped motif: a brief gamma burst followed by a coordinated down-state, expressed synchronously across prefrontal, retrosplenial, and subicular regions. During spontaneous synchronous up-states, which are selectively increased by claustrum stimulation, directionality analyses reveal frequency-specific information flow, with a transient cortical-to-hippocampal influence at slow frequencies and reciprocal gamma-band drive toward cortex, preceding the global silencing. By linking a rapid gamma phase reset to the following down-state, CLAsc activity imposes temporal order on hippocampo–cortical interactions. These results identify the claustrum as a subcortical hub that both synchronizes and biases hippocampo–cortical communication during sleep.