ESTIMATING THE ENDOGENOUS COMPONENT OF THE CIRCADIAN-RHYTHM OF RECTALTEMPERATURE IN HUMANS UNDERGOING NORMAL SLEEP ACTIVITY SCHEDULES/

Continuous recordings have been made of rectal temperature for up to 2 3 consecutive days, using 13 subjects living a normal routine of sleep and activity. A series of purification methods have been developed th at enable the direct effects of sleep and activity upon body temperatu re to be taken into account; this allows a daily estimate of the ''unm asked'' circadian rhythm to be made. Results indicate that the purifie d, unmasked rhythm showed more daily phase variation than the raw (mas ked) data. These findings are discussed with regard to the stabilizing effect upon the measured circadian rhythm that masking factors have, and in terms of estimating the phase variability of the endogenous com ponent of the circadian rhythm.