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OBJECTIVE: The authors investigated the neurobiological basis of poor sleep and daytime fatigue in insomnia. METHOD: (18)FFluorodeoxyglucose positron emission tomography was used to assess regional cerebral glucose metabolism of seven patients with insomnia and 20 healthy subjects. RESULTS: Compared with healthy subjects, patients with insomnia showed greater global cerebral glucose metabolism during sleep and while awake, a smaller decline in relative metabolism from waking to sleep states in wake-promoting regions, and reduced relative metabolism in the prefrontal cortex while awake. CONCLUSIONS: Subjectively disturbed sleep in patients with insomnia is associated with greater brain metabolism. The inability to fall asleep may be related to a failure of arousal mechanisms to decline in activity from waking to sleep states. Further, daytime fatigue may reflect decreased activity in the prefrontal cortex resulting from inefficient sleep.
Nofzinger et al. (Thu,) studied this question.