Insomnia-related complaints correlate with functional connectivity between sensory-motor regions.

According to the hyperarousal theory of insomnia, difficulty in initiating or maintaining sleep occurs as a result of increased cognitive and physiological arousal caused by acute stressors and associated cognitive rumination, placing the individual in a perpetual cycle of hyperarousal and increased sensitivity to sensory stimulation. We tested the hypothesis that difficulty in initiating or maintaining sleep would be associated with increased functional connectivity between primary sensory processing and motor planning regions. Fifty-eight healthy adults (29 men, 29 women) completed a self-report inventory about sleep onset and maintenance problems and underwent a 6-min resting-state functional MRI scan. Bilateral regions of interest (ROIs) were placed in primary visual cortex, auditory cortex, olfactory cortex, and the supplementary motor cortex, and the mean processed signal time course was extracted and correlated with each of the other ROIs. Difficulty in falling asleep was associated with increased functional connectivity between the primary visual cortex and other sensory regions such as the primary auditory cortex, olfactory cortex, and the supplementary motor cortex. The primary auditory cortex also showed greater connectivity with the supplementary motor cortex in those with sleep initiation problems. Problems with sleep maintenance were associated with greater connectivity between the primary visual cortex and the olfactory cortex. Consistent with the predictions of the hyperarousal model, difficulty in falling asleep was associated with greater functional connectivity between primary sensory and supplementary motor regions. Such augmented functional connectivity may contribute to the sustained sensory processing of environmental stimuli, potentially prolonging the latency to sleep.