Surface Shape Differences in Subcortical Areas of Brain May Light Up Our Insight About Insomnia Disorder

Many people suffer from insomnia disorder nowadays. It is mostly described by initiating or continuing sleep problems that cause abnormal sleep duration or quality. In spite of the high rate of such disorder and its adverse effects, pathophysiology of insomnia disorder is poorly understood. Thus, we applied the shape analysis methods to investigate shape differences of subcortical nuclei between healthy subjects and patients. Method Fifty-five patients with insomnia disorder and 49 healthy subjects were selected from the sleep research center at Kermanshah University of Medical Sciences. For every participant, T1-weighted high-resolution MPRAGE pulse sequence collected. After quality assurance and pre-processing, surface-based analysis applied using FIRST algorithm in FSL [1,2]. This algorithm automatically segments subcortical nuclei and models surface by triangular meshes (vertices). To estimate group differences, vertex-wise GLM was applied using nonparametric permutation testing with family-wise error correction. Intracranial surface changes were considered significant at p < 0.05. Results Neuroanatomical alterations were found in bilateral hippocampus, bilateral amygdala, left putamen in participants with insomnia disorders compared to healthy subjects. In addition, in individuals with a subtype of insomnia disorder (i.e., paradoxical insomnia) shrinking were found in left amygdala, left putamen, bilateral hippocampus, and bilateral thalamus comparing to controls (Figurs 1-2).Conclusions Our group comparison demonstrated significant difference in amygdala that plays an important role in emotional reactions, hippocampus which engages in memory coding and consolidation and thalamus and putamen that are effective in regulating the pattern of sleep and wakefulness. Our results shed light for better understanding the pathophysiology of insomnia disorder.