Desynchronization of human circadian rhythms.

In man as well as in animals, diurnal rhythms are based on endogenous, periodic processes which can be considered self-sustained oscillations in a technical sense2). Evidence for this is given by the observation that, underconstant conditions, the rhythm continues a) undamped and b) with a frequency which deviates from that of the earth's rotation6). It is this deviation of the free-running 'circadian '11) period from 24 hours which excludes external cues as possible causes of the rhythm. In many aspects, the whole organism behaves like a single oscillator which obeys the law of oscillation theory. Some findings, however, suggest that the circadian system consists of a multiplicity of oscillators which normally are synchronized with each other but which can become desynchronized under special circumstances13,14). Thishypothesis seems to be supported by recent results from experiments with human subjects which will be discussed below.