Winding down for the night: changes in thalamocortical connectivity before bed are associated with subsequent...

The transition from wakefulness to sleep depends on dynamic thalamocortical interactions that regulate arousal and sensory gating. While thalamic coordination of cortical activity during sleep is well established, little is known about how presleep thalamocortical connectivity relates to subsequent sleep architecture. This study examined whether short-term changes in thalamocortical coupling during the early evening predict polysomnographically measured sleep later that night.

Twenty adults (8 men, 12 women; age 19-39 years) with clinically significant insomnia symptoms completed two resting-state functional MRI scans ~2 hours apart (~6 : 30 and 8 : 30 p.m.) before an overnight in-lab sleep study. Whole-brain seed-to-voxel analyses using a bilateral thalamic region of interest assessed changes in functional connectivity between scans, which were then correlated with polysomnographic sleep-stage metrics [i.e. time in wake, N1, N2, N3, rapid eye movement (REM)].

Increased thalamocortical connectivity with occipital, posterior middle temporal, and left frontal cortices before sleep predicted greater time in N2 sleep, whereas decreased connectivity with insula, putamen, and frontal regions predicted more N3 sleep. Reduced thalamic coupling with the left lateral occipital gyrus predicted greater REM sleep, and decreased thalamocerebellar connectivity was associated with increased wake time while in bed. No associations were observed for N1, total sleep time, or sleep efficiency.

Fluctuations in presleep thalamocortical connectivity predicted distinct features of subsequent sleep architecture. These findings suggest that presleep thalamocortical network dynamics may facilitate some aspects of later restorative sleep the same night, providing insight into how waking brain patterns influence subsequent sleep quality and continuity.