Reduced structural connectivity in Insomnia Disorder

Abstract

Insomnia Disorder is the most prevalent sleep disorder and it involves both sleep difficulties and daytime complaints. The neural underpinnings of Insomnia Disorder are poorly understood.Existing neuroimaging studies are limited by their focus on local measures and specific regions of interests. To address this shortcoming, we applied a data-driven approach to assess differences in whole-brain structural connectivity between adults with Insomnia Disorder and matched controls without sleep complaints. We used diffusion tensor imaging and probabilistic tractography to assess whole-brain structural connectivity and examined group differences using Network-Based Statistics. The results revealed a significant difference in the structural connectivity of the two groups. Participants with Insomnia Disorder showed reduced connectivity in a subnetwork that was largely left lateralized, including mainly fronto-subcortical connections with the insula as a key region. By taking a whole-brain network perspective, our study succeeds at integrating previous inconsistent findings, and our results reveal that reduced structural connectivity of the left insula and the connections between frontal and subcortical regions are central neurobiological features of Insomnia Disorder. The importance of these areas for interoception, emotional processing, stress responses and the generation of slow wave sleep may help guide the development of neurobiologybased models of the highly prevalent condition of Insomnia Disorder.

Consistent altered internal capsule white matter microstructure in insomnia disorder

“…Fronto-subcortical circuits, for example, mediate the disrupting effects of stress on sleep in rodents [ 50 ]. Furthermore, previous studies report that people with insomnia show functional alterations in fronto-subcortical networks [ 51 ] and structural alterations in the fronto-limbic system as indicated by network properties of its white matter connectivity [ 25 , 52 ]. Interestingly, the anterior limb of the internal capsule is surrounded by several structures reported to be involved in insomnia and serves their connectivity.…”

“…These structures include the putamen and the head of the caudate nucleus. Both have been implicated in insomnia [ 25 , 26 , 53 ]. In addition, the anterior internal capsule accommodates fibers that connect more distant areas previously associated with insomnia, notably the OFC [ 20 , 21 ] and the ACC [ 23 , 24 , 54 ].…”

“…A trend was seen in the left hemisphere. Previous studies have reported associations either or both in the left and right hemispheres [ 14–16 , 25 ]. Overall, the findings do not support the hemispheric specificity of the association.…”

Brain structural connectivity network alterations in insomnia disorder reveal a central role of the right angular gyrus

“…One study reported abnormalities associated with ID in the limbic cortico-basal-ganglia circuit and the default-mode network (Wu et al., 2018). The other study reported reduced connectivity strength in ID among the left insular, frontal, and subcortical regions (Jespersen et al., 2019). Limitations of the former study included an unfavorable signal-to-noise ratio owing to the 1.5-Tesla MRI hardware (Hunsche et al., 2001; Okada et al., 2007), while the latter study was limited by the relatively small sample size of 16 people with ID and 14 matched controls.…”

Brain mechanisms of insomnia: new perspectives on causes and consequences

“…Several studies reported associations of sleep quality and quantity in areas that are also suggested by other methods discussed in this section. Jespersen et al (187) used network-based statistics to compare people with insomnia and controls without sleep complaints to reveal a particular reduction in the connectivity in a network with the insula as a key node. Khalsa et al found that sleep quality and duration were associated with fractional anisotropy and/or mean diffusivity in white matter in the anterior cingulum, the orbitofrontal and insula region and the caudate nucleus (202).…”