COMPLETE SUPRACHIASMATIC LESIONS ELIMINATE CIRCADIAN RHYTHMICITY OF BODY-TEMPERATURE AND LOCOMOTOR-ACTIVITY IN GOLDEN-HAMSTERS

The effects of suprachiasmatic and control lesions on the circadian rh ythms of locomotor activity and body temperature were studied in golde n hamsters (Mesocricetus auratus) maintained in constant light as well as constant darkness. Large suprachiasmatic lesions, but not control lesions, eliminated circadian rhythmicity in locomotor activity as wel l as in body temperature. Analysis of the ''robustness'' of the rhythm s of locomotor activity and body temperature in unlesioned and lesione d animals suggests that, because body temperature rhythmicity is more robust than locomotor rhythmicity, lesions that spare a small number o f suprachiasmatic cells might abolish the latter but not the former. O ur results do not support the hypothesis that the body temperature rhy thm is controlled by a circadian pacemaker distinct from the main pace maker located in the suprachiasmatic nuclei.