title: The process of awakening: a PET study of regional brain activity patterns mediating the re-establishment of alertness and consciousness.
abstract: Awakening from sleep entails rapid re-establishment of consciousness followed by the relatively slow (20-30 min later) re-establishment of alertness--a temporal dissociation that facilitates specification of the physiological underpinnings of each of these facets of the awakening process. H(2)(15)O PET was used to assess changes in regional cerebral blood flow (rCBF) upon awakening from stage 2 sleep. Cerebral blood flow (CBF) was most rapidly re-established in centrencephalic regions (e.g. brainstem and thalamus), suggesting that the reactivation of these regions underlies the re-establishment of conscious awareness. Across the ensuing 15 min of wakefulness, further increases in CBF were evident primarily in anterior cortical regions, suggesting that the dissipation of sleep inertia effects (post-awakening performance and alertness deficits) is effected by reactivation of these regions. Concomitant shifts in correlation patterns of regional brain activity across the post-awakening period [in particular, a waning negative correlation between prefrontal cortex and mesencephalic reticular formation (RF) activity, and a waxing positive correlation between prefrontal cortex and ventromedial caudate nucleus (CAUD) activity] suggest that the post-awakening reversal of sleep inertia effects may be mediated by more than mere reactivation--it may also involve the functional reorganization of brain activity. Conversely, stable post-awakening correlations--such as those found between the anterior cingulate cortex (ACC) and most other brain regions--may denote the pattern of functional connectivity that underlies consciousness itself.
authors.affiliation: Department of Behavioral Biology, Walter Reed Army Institute of Research, Washington, DC 20307-5100, USA. thomas.balkin@na.amedd.army.mil
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Balkin
authors.forename: Allen R
authors.initials: AR
authors.lastname: Braun
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Wesensten
authors.forename: Keith
authors.initials: K
authors.lastname: Jeffries
authors.forename: Mary
authors.initials: M
authors.lastname: Varga
authors.forename: Paul
authors.initials: P
authors.lastname: Baldwin
authors.forename: Gregory
authors.initials: G
authors.lastname: Belenky
authors.forename: Peter
authors.initials: P
authors.lastname: Herscovitch
mesh_terms: D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging* / Q000502:physiology; D001931:Brain Mapping / Q000379:methods; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003243:Consciousness / Q000502:physiology*; D006801:Humans; D008297:Male; D012894:Sleep Stages / Q000502:physiology*; D014055:Tomography, Emission-Computed / Q000379:methods / Q000706:statistics & numerical data; D014851:Wakefulness / Q000502:physiology*