Sleep-Wake Differences in Relative Regional Cerebral Metabolic Rate for Glucose among Patients with Insomnia Compared with Good Sleepers

Abstract

Insomnia was characterized by regional alterations in relative glucose metabolism across NREM sleep and wakefulness. Significant group-by-state interactions in relative rCMR suggest that insomnia is associated with impaired disengagement of brain regions involved in cognition (left frontoparietal), self-referential processes (precuneus/posterior cingulate), and affect (left middle frontal, fusiform/lingual gyri) during NREM sleep, or alternatively, to impaired engagement of these regions during wakefulness.

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

“…See Table 1 for a complete list of brain regions showing group differences in relative rCMR glc during wake and NREM sleep in PI compared to GS. Third, no group differences were identified in semi-quantitative whole-brain glucose metabolism [52]. Although smaller sleep-wake differences can be explained within a hyperarousal framework, lower relative rCMR glc in patients with PI compared with GS during NREM sleep in limbic brain regions is more difficult to explain within this framework.…”

“…Healthy sleep states oscillate between quiet (NREM) and active (REM) sleep states. During healthy NREM sleep, whole-brain glucose metabolism decreases relative to wake [52]. The greatest reductions occur in heteromodal regions of the frontal and parietal cortices, posterior cingulate cortex, and thalamus [52,97].…”

“…During healthy NREM sleep, whole-brain glucose metabolism decreases relative to wake [52]. The greatest reductions occur in heteromodal regions of the frontal and parietal cortices, posterior cingulate cortex, and thalamus [52,97]. Thus, the NREM sleep state is most consistent with sector 4 where sleep drive is high, wake drive is low, and conscious awareness is low.…”

“…High-density EEG studies suggest that insomnia may be associated with heightened region-specific brain activity during quite wake, but the specific brain regions involved remain unclear [45,46]. Altered activity and functional connectivity during quiet wake occurs most consistently in primary sensory-motor regions, frontoparietal regions, and nodes of the default mode network [52,61,63,64,75]. This pattern may be explained by dysfunction of inhibitory processes in the cortex.…”

“…Compared to GS, NREM sleep in PI is associated with lower blood flow, particularly in the basal ganglia, frontal medial, occipital, and parietal regions during NREM sleep [49]. A more recent study demonstrated that insomnia was associated with lower relative regional glucose metabolism in several limbic brain regions during NREM sleep [52]. These patterns may reflect heightened sleep drive during PSG-defined NREM sleep in those regions.…”