Impact of CBTI on Cerebral Glucose Metabolism

Somnoimaging is an approach in sleep medicine that combines neuroimaging techniques with established sleep research methods to better characterize sleep-wake states and study sleep-related constructs across those states. We used the fludeoxyglucose positron emission tomography (FDG-PET) method to investigate how CBTI impacted cerebral glucose metabolism during sleep and wakefulness in individuals with insomnia (N=27). We replicated previous findings suggesting that CBTI improves self-reported symptoms of insomnia and dysfunctional beliefs about sleep but found no significant differences in whole-brain or voxel-wise relative regional glucose metabolism as a result of CBTI. Followup analyses showed that (1) participants with greater pre-to-post treatment reduction in dysfunctional beliefs about sleep had a significant increase in relative glucose metabolism in the caudate following treatment, (2) individuals with greater relative glucose metabolism in the precentral gyrus at baseline had higher insomnia severity post-treatment, and (3) participants who experienced greater pre-to-post treatment reduction in insomnia severity following treatment had a more pronounced sleep-wake difference in relative glucose metabolism in the precuneus. Our findings may suggest that (1) targeting dysfunctional beliefs about sleep during CBTI may help normalize caudate nucleus activity across sleep-wake states, (2) greater relative glucose metabolism in the precentral gyrus may represent a biomarker of hyperarousal that predicts poorer response to CBTI, and (3) successful CBTI restores the polarity of relative glucose metabolism across sleep-wake states in individuals with insomnia in the posterior hotzone of consciousness.