Evidence for age-related changes in the circadian activity rhythm of the diurnal primate Callithrix jacchus: a case report

AbstractMany cross-sectional studies have shown that circadian rhythms change with age, but such age-related modifications are gradual and may be insufficiently described by cross-sectional studies. In this case study, circadian activity rhythm (CAR) was evaluated longitudinally, in both LD (12:12) and LL conditions, on two occasions in a single male marmoset: when ‘adult’ (3 y.o.) and when ‘old’ (9 y.o.). When adult, the CAR synchronized with positive phase angles for the onset and offset of activity. In LL, the rhythm free-ran with τ   24 h. We conclude that aging is associated with attenuation of photic synchronization and expression of CAR in LL in the marmoset. Further studies with a ...