Claustral pathway coordinates distributed cortical dynamics with hippocampal output during sleep to promote memory consolidation

The claustrum is a subcortical structure that connects various cortical regions and is thought to orchestrate distributed cortical activity. During sleep, claustral neurons play a role in memory consolidation, primarily by influencing cortical dynamics. However, the claustrum also sends projections to the subicular complex, a key output node within the hippocampus, suggesting a potential role in regulating both cortical state and the communication between the hippocampus and cortex during sleep.

In this study, the authors discovered a specific group of claustral neurons, termed CLAsc, which primarily targets the subicular complex. These neurons are more active during slow wave sleep and adapt to the changing patterns of cortical and subicular sleep activity. When the CLAsc neurons were activated using optogenetics during sleep following learning, they improved spatial memory consolidation without altering the occurrence of ripples or the coupling of slow oscillation spindles.

Instead, the activation of CLAsc neurons induced a predictable pattern across prefrontal, retrosplenial, and subicular regions.

This pattern began with a brief gamma-rich "Up" state, followed by a coordinated "Down" state. During this gamma-rich phase, interareal coherence increased, gamma bursts became synchronized, and directed interactions were temporarily reorganized. Notably, there was a heightened prefrontal-to-subicular connection. These observations indicate that the claustrum acts as a state-dependent coordinator, converting ongoing cortical and hippocampal output activity into synchronized network transitions during sleep.

This suggests a potential circuit mechanism by which widespread brain states may facilitate memory consolidation.