Abstract
Using digital techniques for signal analysis—the correlogram and a high-resolution analysis of time series, maximum-entropy spectral analysis (MESA)—we have detected both circadian and ultradian rhythms in the locomotor activity of free-runningper 0 males and in females lacking theper locus (per −; heterozygous for two deficiencies, each of which deletes the gene). Over half theper 0 individuals and half theper − individuals tested were rhythmically active, with dominant periods ranging from 4 to 22 h; most of the significantly rhythmicper 0 andper − flies clearly exhibited multiple periodicities. This novel pattern of rhythmic behavior is thoroughly distinct from the wild-type pattern. One hypothesis suggested by our observations is that theper + gene products mediate the coupling of multiple ultradian oscillators to produce wild-type circadian rhythms.