Functional connectivity changes between parietal and prefrontal cortices in primary insomnia patients: evidence from resting-state fMRI

Abstract

BackgroundPrimary insomnia can severely impair daytime function by disrupting attention and working memory and imposes a danger to self and others by increasing the risk of accidents. We speculated that the neurobiological changes impeding working memory in primary insomnia patients would be revealed by resting-state functional MRI (R-fMRI), which estimates the strength of cortical pathways by measuring local and regional correlations in blood oxygen level dependent (BOLD) signs independent of specific task demands.MethodsWe compared the R-fMRI activity patterns of 15 healthy controls to 15 primary insomnia patients (all 30 participants were right-handed) using a 3.0 T MRI scanner. The SPM8 and REST1.7 software packages were used for preprocessing and analysis. Activity was expressed relative to the superior parietal lobe (SPL, the seed region) to reveal differences in functional connectivity to other cortical regions implicated in spatial working memory.ResultIn healthy controls, bilateral SPL activity was associated with activity in the posterior cingulate gyrus, precuneus, ventromedial prefrontal cortex, and superior frontal gyrus, indicating functional connectivity between these regions. Strong functional connectivity between the SPL and bilateral pre-motor cortex, bilateral supplementary motor cortex, and left dorsolateral prefrontal cortex was observed in both the control group and the primary insomnia group. However, the strength of several other functional connectivity pathways to the SPL exhibited significant group differences. Compared to healthy controls, connectivity in the primary insomnia group was stronger between the bilateral SPL and the right ventral anterior cingulate cortex, left ventral posterior cingulate cortex, right splenium of the corpus callosum, right pars triangularis (right inferior frontal gyrus/Broca’s area), and right insular lobe, while connectivity was weaker between the SPL and right superior frontal gyrus (dorsolateral prefrontal cortex).ConclusionPrimary insomnia appears to alter the functional connectivity between the parietal and frontal lobes, cortical structures critical for spatial and verbal working memory.

Abnormal Neural Network of Primary Insomnia: Evidence from Spatial Working Memory Task fMRI

“…In the current study, comparison of activated brain regions in the spatial working memory task state between PI patients and controls indicated that activation patterns were consistent with these prior observations. Because the most fundamental characteristic of a spatial working memory is the synergistic effect between the parietal lobe and prefrontal lobe [21] , activation patterns in the bilateral superior parietal lobules and bilateral frontal lobes in the current study notably demonstrated the linkage between such activation and spatial working memory. These findings are concordant with the results of scales score, and weakened activation in the parahippocampal gyrus and bilateral temporal lobes was observed in cases of memory deterioration [21] .…”

“…Because the most fundamental characteristic of a spatial working memory is the synergistic effect between the parietal lobe and prefrontal lobe [21] , activation patterns in the bilateral superior parietal lobules and bilateral frontal lobes in the current study notably demonstrated the linkage between such activation and spatial working memory. These findings are concordant with the results of scales score, and weakened activation in the parahippocampal gyrus and bilateral temporal lobes was observed in cases of memory deterioration [21] . Insomnia is a unique and complex physiological process involving interrelationships between varied brain regions, neural networks and neuroendocrine mechanisms.…”

Neuroimaging Insights into Insomnia

“…This abnormal pattern of insula coactivation may indicate that interoceptive awareness of bodily states, one of the established roles of the insula [60,61], is impaired in patients with insomnia. However, the lack of simultaneous EEG recordings to ensure defined states of sleep or wakefulness [56][57][58]62], coupled with application of liberal statistical thresholds, may partially explain variability in findings across resting-state fMRI studies in insomnia.…”

Hyperarousal and Beyond: New Insights to the Pathophysiology of Insomnia Disorder through Functional Neuroimaging Studies

“…One study found that individuals with PI had lower functional connectivity within the default mode network in specific areas including the medial prefrontal cortex with the right medial temporal lobe and the left medial temporal lobe with the left inferior parietal cortices [75]. Another study that used the superior parietal lobule (a major node of both executive control and default mode networks) as the seed region found that patients with PI, compared to GS, had higher connectivity of this region with the anterior cingulate, left posterior cingulate, right inferior frontal gyrus, right insula, and precuneus [76]. These are all regions of the brain involved in conscious awareness.…”