The authors investigated the neurobiological basis of poor sleep and daytime fatigue in insomnia.
[(18)F]Fluorodeoxyglucose positron emission tomography was used to assess regional cerebral glucose metabolism of seven patients with insomnia and 20 healthy subjects.
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.
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.
"Sleep research indicates that insomnia is highly associated with abnormal brain activity. Patients with insomnia have been found to exhibit hyperarousal  or greater global brain metabolism while awake, as compared to sleep state . In particular, their resting EEG activity in both the alpha band and the nonalpha band is higher than that of normal subjects, and there is a significant positive correlation between hyperarousal scores and alpha activity on the left side when patients' eyes are open . "
"Furthermore , altered function in fronto - subcortical circuits has been suggested to be involved in the pathophysiology of insomnia [ Cano et al . , 2008 ; Nofzinger et al . , 2004 ] . While the exact neurobiological mechanisms underlying insomnia remain unclear , it seems reasonable to assume that reduced white matter integrity in the anterior internal capsule may contribute to disturbed sleep - specific fronto - subcortical neuronal synchronization and , thus , to the experience of insomnia . It has also been su"
"Neuroimaging findings in people with insomnia also support a hyperarousal hypothesis. In PET studies primary insomniacs, relative to healthy controls, showed greater cerebral glucose metabolism during sleep, while awake, and at the transition from wake to sleep and particularly in the ascending reticular activation system (ARAS) (Nofzinger et al. 2004). The hypothalamus, thalamus, amygdala, hippocampus , and prefrontal cortices were also activated during sleep. "
[Show abstract][Hide abstract] ABSTRACT: Insomnia is a prevalent sleep disorder that is typically comorbid with medical, psychiatric, and other sleep disorders. Yet, it is a disorder with its own course and morbidity that can persist if untreated. This chapter describes the physiological correlates of insomnia expressed during sleep and during the daytime. Together, the data from nighttime and daytime electrophysiologyelectrophysiology , event-related brain potential recordingevent-related brain potential recording , neuroimaging studiesneuroimaging studies , sympathetic nervous systemsympathetic nervous system , and HPA axis monitoringHPA axis monitoring all suggest that insomnia is a 24 h disorder of hyperarousaldisorder of hyperarousal .
Current Topics in Behavioral Neurosciences 06/2014; 21. DOI:10.1007/7854_2014_324
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