New techniques for the analysis of the human sleep-wake cycle

Two new techniques for the analysis of the human sleep-wake cycle are presented and illustrated. The first is based on a wrist-worn solid-state activity monitor which can record movement activity for prolonged time periods. The method has been applied to document phase-shifts of the rest-activity cycle after crossing time-zones; to analyze the effect of hypnotic drugs on movements during sleep; and to record the severe disruption of sleep and waking in narcolepsy. The second technique consists of all-night spectral analysis of the sleep EEG. In addition to conventional sleep stage scoring by visual analysis, power density values of the sleep EEG are computed for 4-sec epochs in the range of 0.25-25.0 Hz. The spectra provide a more refined and quantitative description of the sleep process than analysis of the sleep stage distribution. The method revealed within individual sleep stages significant trends through the night as well as specific changes induced by sleep deprivation. Spectral analysis was also applied for determining the effect of benzodiazepine hypnotics on the sleep EEG, and for documenting subtle, residual drug effects in the following drug-free night.