Entrainment range affected by the heterogeneity in the amplitude relaxation rate of suprachiasmatic nucleus neurons**Project supported by the National Natural Science Foundation of China (Grant Nos. 11875042, 11505114, and 10975099) and the Program for Professor of Special Appointment (Orientational Scholar) at Shanghai Institutions of Higher Learning, China (Grant Nos. QD2015016 and D-USST02).

Abstract

Adaption of circadian rhythms in behavioral and physiological activities to the external light–dark cycle is achieved through the main clock, i.e., the suprachiasmatic nucleus (SCN) of the brain in mammals. It has been found that the SCN neurons differ in the amplitude relaxation rate, which represents the rigidity of the neurons to the external amplitude disturbance. Thus far, the appearance of that difference has not been explained. In the present study, an alternative explanation based on the Poincaré model is given which takes into account the effect of the difference in the entrainment range of the SCN. Both our simulation results and theoretical analyses show that the largest entrainment range is obtained with suitable difference in the case that only a part of SCN neurons are sensitive to the light information. Our findings may give an alternative explanation for the appearance of that difference (heterogeneity) and shed light on the effects of the heterogeneity in the neuronal properties on the collective behaviors of the SCN neurons.