Time course of EEG power density during long sleep in humans.
In nine subjects sleep was recorded under base-line conditions with a habitual bedtime (prior wakefulness 16 h; lights off at 2300 h) and during recovery from sleep deprivation with a phase-advanced bedtime (prior wakefulness 36 h; lights off at 1900 h). The duration of phase-advanced recovery sleep was greater than 12 h in all subjects. Spectral analysis of the sleep electroencephalogram (EEG) revealed that slow-wave activity (SWA; 0.75-4.5 Hz) in non-rapid-eye-movement (NREM) sleep was significantly enhanced during the first two NREM-REM sleep cycles of displaced recovery sleep. The sleep stages 3 and 4 (slow-wave sleep) and SWA decreased monotonically over the first three and four NREM-REM cycles of, respectively, base-line and recovery sleep. The time course of SWA in base-line and recovery sleep could be adequately described by an exponentially declining function with a horizontal asymptote. The results are in accordance with the two-process model of sleep regulation in which it is assumed that SWA rises as a function of the duration of prior wakefulness and decreases exponentially as a function of prior sleep. We conclude that the present data do not provide evidence for a 12.5-h sleep-dependent rhythm of deep NREM sleep.
Dijk
D J
DJ
Institute of Pharmacology, University of Zurich, Switzerland.
Brunner
D P
DP
Borbély
A A
AA
D000328:Adult; D000704:Analysis of Variance; D003198:Computer Simulation; D004569:Electroencephalography; D006801:Humans; D008297:Male; D008954:Models, Biological; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology; D013997:Time Factors