Physiology & behavior
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Physiology & behavior · Aug 2000
Entrainment of the rat motor activity rhythm: effects of the light-dark cycle and physical exercise.
The circadian system is believed to be composed of a population of oscillators that couple together and generate a single rhythm. If this coupling is not strong enough, the circadian system can be dissociated into two or more groups of oscillators, and this is manifested in a dissociation of the overt rhythm into at least two circadian components. This study aims to examine the influence of factors, such as the difference in impact between T and tau, light intensity, and access to a running wheel, on the distribution of motor activity throughout the light-dark (LD) cycle and the dissociation of the rhythm. ⋯ Results show that the distribution of motor activity throughout the cycle and the after effects observed in the rhythm under DD depended on light intensity and access to the wheel. Moreover, under T23, some rats showed two simultaneous circadian components whose manifestation also depended on the experimental conditions. The results indicate that the strength of circadian entrainment to LD cycles in the rat depends on three factors: the period length of the LD cycle, light intensity used during the light phase, and access to a running wheel.