A multi-window spectral analysis of circadian rhythms

The authors investigate circadian rhythms by using a new multi-window spectral analysis computer algorithm which detects spectral peaks not resolvable by ordinary spectral analysis methods. Temperature data from two monkeys were examined with the new spectral analysis program to investigate the presence of circadian rhythms and their harmonics and to examine the data for longer period oscillations. Thirty-three day records sampled once per hour were used. Data from both monkeys show well resolved spectral peaks at periods of 24, 12, and 8 h which represents the basic circadian rhythm and its second and third harmonics. The peaks located at 24, 12, and 8 h illustrate the ability of the new spectral analysis program to resolve peaks already resolved by standard spectral analysis methods. Peaks found at 3.125 and 9.375 days in one monkey confirm the prediction of the simulation model that these low frequencies may exist in some cases