Effects of square-wave and simulated natural light-dark cycles on hamster circadian rhythms

Transitions between light and dark affect the circadian rhythms in hamsters. This was gleaned from an experiment in which circadian rhythms of activity and body temperature were analyzed in male Syrian hamsters under square-wave and simulated natural light-dark cycles. Results show that the hamsters exhibited different circadian entrainment behavior under square-wave and simulated natural light-dark cycles, indicating that gradual and abrupt transitions between light and dark may generate different temporal cues.