title: Two circadian rhythms in the human electroencephalogram during wakefulness.
abstract: The influence of the circadian pacemaker and of the duration of time awake on the electroencephalogram (EEG) was investigated in 19 humans during approximately 40 h of sustained wakefulness. Two circadian rhythms in spectral power density were educed. The first rhythm was centered in the theta band (4.25-8.0 Hz) and exhibited a minimum approximately 1 h after the onset of melatonin secretion. The second rhythm was centered in the high-frequency alpha band (10.25-13.0 Hz) and exhibited a minimum close to the body temperature minimum. The latter rhythm showed a close temporal association with the rhythms in subjective alertness, plasma melatonin, and body temperature. In addition, increasing time awake was associated with an increase of power density in the 0.25- to 9.0-Hz and 13.25- to 20. 0-Hz ranges. It is concluded that the waking EEG undergoes changes that can be attributed to circadian and homeostatic (i.e., sleep-wake dependent) processes. The distinct circadian variations of EEG activity in the theta band and in the high-frequency alpha band may represent electrophysiological correlates of different aspects of the circadian rhythm in arousal.
authors.affiliation: Section on Biological Rhythms, Intramural Research Program, National Institute of Mental Health, Bethesda, Maryland 20892, USA. aschbach@box-a.nih.gov
authors.forename: D
authors.initials: D
authors.lastname: Aeschbach
authors.forename: J R
authors.initials: JR
authors.lastname: Matthews
authors.forename: T T
authors.initials: TT
authors.lastname: Postolache
authors.forename: M A
authors.initials: MA
authors.lastname: Jackson
authors.forename: H A
authors.initials: HA
authors.lastname: Giesen
authors.forename: T A
authors.initials: TA
authors.lastname: Wehr
mesh_terms: D000328:Adult; D001683:Biological Clocks; D001831:Body Temperature; D001833:Body Temperature Regulation; D002940:Circadian Rhythm / Q000502:physiology*; D004569:Electroencephalography; D005260:Female; D006706:Homeostasis; D006801:Humans; D008297:Male; D008550:Melatonin / Q000097:blood / Q000378:metabolism*; D014851:Wakefulness / Q000502:physiology*
chemical_list: D008550:Melatonin