Enhanced volume and resting-state functional connectivity of amygdala subregions in patients with insomnia disorder

Patients with insomnia disorder are particularly susceptible to emotional disturbances. However, the amygdala, a key region for emotional processing, remain poorly understood in this population. We aimed to investigate the functional and structural abnormalities in amygdala subregions to provide a more nuanced understanding of the emotional disturbances in insomnia patients. We ultimately analyzed MRI data and clinical scales from 35 individuals (24 female) with insomnia disorder and 28 healthy controls (20 female). The resting-state functional connectivity maps between whole brain regions with amygdala subregions were obtained from functional magnetic resonance imaging of each subject. Additionally, FreeSurfer was employed to automatically extract whole amygdala and amygdala subregion volumes from T1-weighted imaging. We compared the connectivity maps and volumes with two-sample t-test and generalized linear models between the two groups, respectively. Statistically significant indicators were selected for correlation analysis with scales. Insomnia patients showed heightened resting-state functional connectivity compared to controls in the following areas: between the left basolateral amygdala and the bilateral cerebellum, posterior cingulate cortex, and left superior frontal gyrus; between the right centromedial amygdala and the right caudate nucleus and medial frontal gyrus; and between the left superficial amygdala and the left medial superior frontal gyrus, right cerebellum, and left precuneus. Notably, connectivity between the basolateral amygdala and the superior frontal gyrus was positively correlated with depressive levels. Only the superficial amygdala volume showed increase in patients. The impairments of functional and structural in amygdala subregions may provide mechanistic insights into the pathogenesis of insomnia disorder.