Circadian rhythms in human performance and affective state.

After reviewing earlier contributions to the understanding of the physiology of circadian system in man, in particular his cognitive aspects, we report on own studies obtained using the fractional desynchronization technique to induce internal desynchronization in man. These results show that in temporal isolation studies, rhythms in some performance measures follow a period of about 21 hours, even when the subject's physiological rhythms are apparently synchronized to the 24 hour day. These data are discussed in relationship to current theoretical frameworks in chronobiology.