Ultradian rhythms in task performance, self-evaluation, and EEG activity.

Abstract

Many studies have shown the existence of cycles of approximately 90 to 100 minutes (corresponding to Kleitman's basic rest-activity cycle) and several hours ('slow ultradian rhythm' cycles). EEG power spectra, mood, performance, and self-evaluation of performance were measured every 15 minutes for 9 hours for 10 male university students. Principal component analysis was applied to extracted ultradian fluctuations in EEG activity, task performance, and the subjective variables. The analysis indicated that two common temporal fluctuations were present, one in the behavioral and subjective variables, and the other in EEG activity. Spectral analysis indicated that the former fluctuated at a rate of 12 cycles per day (corresponding to basic rest-activity cycle), and the latter was comprised of both a slower (6 cycles per day) and a faster (10 to 18 cycles per day) cycle, thereby supporting the multioscillator hypothesis of ultradian rhythm.