Nonphotic Clock Resetting in Mice

Abstract

The circadian clock regulates many aspects of body function including the daily rest/activity cycle and sleep/wake cycle. To stay in synchrony with the environmental light/dark cycle the clock must be reset periodically and environmental light itself is the main stimulus that achieves this resetting. However, other stimuli that are nonphotic (non-light) can reset the circadian clock. a recentstudy has shown that when hamster circadian rhythms are entrained to a daily cycle of bright light and dim light (as opposed to bright light and darkness), their rhythm shifts when they undergo a single abrupt transition to continuous darkness in the middle of the bright phase. We decided to test whether mice would show clock resetting under these conditions since apparently no sustained physical activity is required.