Increased connectivity of the anterior cingulate cortex is associated with the tendency to awakening during N2 sleep in patients with insomnia disorder

To investigate the relationship between sleep transition dynamics and stage-specific functional connectivity (FC) of the anterior cingulate cortex (ACC) in patients with insomnia disorder (ID).Simultaneous electroencephalography-functional magnetic resonance imaging (EEG-fMRI) data from 37 patients with ID and 30 well-matched healthy controls (HCs) were recorded during wakefulness and different sleep stages and subsequently analyzed. A Markov chain model was used to estimate the transition probability between each stage. The FC between the ACC (set as the seed) and voxels across the whole brain was calculated. A linear mixed effect model was used to determine the group-by-stage interaction of the seed-based connectivity. The correlation between the sleep-stage transition probability and the ACC-based connectivity was explored.Patients with ID exhibited a higher likelihood of transitioning from N2 to wakefulness than HCs. A significant group-by-stage interaction of connectivity with the bilateral ACC was observed in the cerebellar, subcortical, and cortical regions. Moreover, a significant positive correlation was found in patients with ID between the transition probability from N2 to wakefulness and the FC of the ACC with the anterior cerebellum in N2 (r = 0.48).This exploratory analysis indicates that enhanced FC between the ACC and cerebellum represents a potential neural pathway underlying the greater likelihood of patients with ID waking during N2 sleep. These findings contribute to an emerging framework that reveals the link between sleep maintenance difficulty and ACC function, further highlighting the possibility that N2 sleep is a therapeutic target for meaningfully reducing sleep disruption.