In order to clarify the neural correlates and brain functions during non-rapid eye movement (NREM) sleep, regional cerebral blood flow (rCBF) were measured using positron emission tomography (PET) in healthy male subjects. During light NREM sleep, the rCBF in the midbrain, in contrast to that in the pons and thalamic nuclei, did not decrease when compared to that during wakefulness, while rCBF decreased in the left medial frontal gyrus, left inferior frontal gyrus, and left inferior parietal gyrus of the neocortex. During deep NREM sleep, the rCBF in the midbrain tegmentum decreased and there was a marked and bilateral decrease in the rCBF in all neocortical regions except for the peri-rolandic areas and the occipital lobe. Thus, the activity of the midbrain reticular formation may be maintained during light NREM sleep. Furthermore, selective deactivation of heteromodal association cortices including those related to language, may occur during NREM sleep, which supports the recent theory that sleep is a local, use-dependent process of the brain.
ASJC Scopus subject areas