Cognitive-emotional and spontaneous neural activity correlates with sleep misperception in insomnia with normal sleep duration.

Insomnia disorder is clinically heterogeneous, with variation in objective sleep duration, sleep perception, cognitive-emotional features, and spontaneous neural activity. We examined whether insomnia with normal sleep duration (INSD) has a distinct behavioral and neural profile relative to insomnia with short sleep duration (ISSD). In 233 participants (100 healthy controls, 67 INSD, 66 ISSD), we assessed objective and diary-based sleep, presleep arousal, and emotion regulation; resting-state fMRI was additionally acquired in a subset of 133 patients with insomnia. Analyses included group comparisons, phenotype-specific associations, moderated mediation, voxel-wise z-standardized amplitude of low-frequency fluctuation (zALFF), and exploratory brain-behavior partial least squares (PLS). Both insomnia groups reported poorer subjective sleep than controls. As expected from the phenotype definitions, INSD showed greater sleep misperception than ISSD; the novel findings were that INSD also showed greater presleep cognitive arousal and brooding, distinct regional zALFF alterations, and a conditional indirect association linking brooding to sleep misperception via presleep cognitive arousal that was evident in INSD but not ISSD. Compared with ISSD, INSD showed higher zALFF in the left insula, left hippocampus, and right precuneus, and lower zALFF in the right middle occipital gyrus. Exploratory PLS linked this INSD-like zALFF pattern to a behavioral profile dominated by sleep misperception and presleep cognitive arousal, mainly at the phenotype level. These findings suggest that INSD involves convergent cognitive-emotional and neural features related to sleep misperception, while causal and individual-prediction claims remain premature.