Aging-related changes on social synchronization of circadian activity rhythm in a diurnal primate (Callithrix jacchus)

ABSTRACT

The input of environmental time cues and expression of circadian activity rhythms may change with aging. Among nonphotic zeitgebers, social cues from conspecific vocalizations may contribute to the stability and survival of individuals of social species, such as nonhuman primates. We evaluated aging-related changes on social synchronization of the circadian activity rhythm (CAR) in a social diurnal primate, the common marmoset. The activity of 18 male marmosets was recorded by actiwatches in two conditions. (1) Experimental – 4 young adult (5 ± 2 yrs of age) and 4 older (10 ± 2 yrs of age) animals maintained under LD 12/12 h and LL in a room with full insulation for light but only partial insulation for sound from vocalizations of conspecifics maintained outdoors in the colony; and (2) Control – 10 young adult animals maintained outdoors in the colony (5 animals as a control per age group). In LL, the CAR of young adults showed more stable synchronization with controls. Among the aged marmosets, two free-ran with τ > 24 h, whereas the other two showed relative coordination during the first 30 days in LL, but free-ran thereafter. These differences were reflected in the “social” phase angles (ψ_on and ψ_off) between rhythms of experimental and control animal groups. Moreover, the activity patterns of aged animals showed lower social synchrony with controls compared to young adults, with the time lags of the time series between each experimental group and control group being negative in aged and positive in young adult animals (t-test, p < 0.05). The index of stability of the CAR showed no differences according to age, while the intradaily variability of the CAR was higher in the aged animals during LD-resynchronization, who took additional days to resynchronize. Thus, the social modulation on CAR may vary with age in marmosets. In the aged group, there was a lower effect of social synchronization, which may be associated with aging-related changes in the synchronization and generation of the CAR as well as in system outputs.

KEYWORDS:

• Circadian activity rhythm
• aging
• social entrainment
• nonphotic cues
• behavioral rhythms
• marmosets

Acknowledgements

This article is dedicated to Prof. Dr. Alexandre Menezes for the valuable contribution to the chronobiological studies in marmosets. We would like to thank Antônio Barbosa, Luís do Nascimento, Geniberto dos Santos, José Rubens de Souza and Edinólia Rodrigues for technical support at the Primatology Colony of UFRN. We also thank the support on the care of animals to our esteemed colleagues Galileu Borges, Maria Luiza Cruz, Rosane Lampert e Sabinne Galina. Our thanks extend to the Postgraduate Program in Psychobiology at UFRN.

Declaration of interest statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

This work was supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Universidade Federal do Rio Grande do Norte (UFRN).