BIOLOGICAL OSCILLATOR SYSTEM AND THE DEVELOPMENT OF SLEEP-WAKING BEHAVIOR DURING EARLY INFANCY

Abstract

The sleep-waking behavior of a male [human] infant, with normal pregnancy, delivery and Apgar score, was observed from birth for 4 mo. of age. The infant was allowed to sleep and wake according to his own schedule and was fed only if his behavior was judged as a feeding demand. Using computerized analysis, it was demonstrated that the spontaneous sleep-waking behavior was driven by 2 endogenous rhythms, an ultradian cycle and a circadian one. While the ultradian rhythm was established at term showing a mean period of 4 h, the circadian variation developed during the 1st 3 mo. Further evidence that both rhythms do not run independently, but apparently constitute a system of connected oscillators is provided. During the nocturnal phase of the circadian rhythm, the ultradian rhythm decelerated. During the diurnal phase the ultradian cycle was accelerated. A computerized model of both connected oscillators was developed. Theoretically predicted sleep-waking behavior was compared to the behavior observed in the study infant. During postnatal development the coupled rhythms cause characteristic periodicities of the sleep-waking pattern. The different periodicities may be considered as a structure timing information process in the developing brain.