Time-Dependent Regulation of Sleep-Wakefulness and Electroencephalographic Characteristics by Spontaneous Running in Male Mice.

The relationship between physical activity and sleep quality is a critical area of investigation, given the importance of both behaviours for health and disease. Despite the common use of running wheels to assess circadian rhythms and exercise, their impact on sleep has not been thoroughly explored. Here, we present a detailed analysis of how voluntary running affected sleep/wakefulness duration, architecture and electrophysiological characteristics in mice. Sequential electroencephalogram (EEG) assessments revealed that voluntary running elicits a progressive alteration in sleep/wake configurations, including a reduction in overall daily sleep time and an enhancement in sleep/wakefulness consolidation. These modifications exhibited a temporal association with the intensity of running activities. The observed changes in sleep/wakefulness duration and architecture partially persist even after the discontinuation of running. Spontaneous running also gradually changed the amplitude and/or frequency of EEG theta power not only during the running phase but also in rapid eye movement sleep (REMS). In vivo endoscopic calcium imaging in freely behaving mice revealed that running and REMS were accompanied by the activation of largely shared yet distinctive neuronal cohorts within the hippocampal CA1 region, concomitant with EEG theta oscillations during both behaviours. These findings highlight the dynamic nature of sleep/wakefulness regulation in response to voluntary exercise and suggest that physical activity played a pivotal role in modulating sleep need and the daily balance between sleep and wakefulness.