Out of the dark, how daytime light influences sleep and supports circadian rhythms

Daytime light makes the four-striped grass mouse *Rhabdomys pumilio* sleep better and strengthens its internal body clock—and researchers are now using this unusual rodent to uncover why bright days benefit human health. Most people experience disrupted sleep or circadian rhythms at some point, which can harm mental and physical health. Light is the main controller of these systems, and bright days help keep our internal clocks robust and less vulnerable to disruptive light at night. But the underlying mechanisms remain unclear because standard lab mice are nocturnal and avoid light, making them poor models for humans. This project fills that gap by studying *Rhabdomys*, a day-active rodent that naturally seeks light and shows the same therapeutic benefits from bright days that humans do. If successful, this fundamental research will reveal how daytime light alters sleep and circadian rhythms from the molecular to the behavioural level, and identify the specific cells and circuits involved. The findings could inform new treatments for attention disorders, sleep problems, and circadian disruption, as well as guide architectural design of lighting in homes, hospitals, and workplaces. Because this is curiosity-driven fundamental science, immediate applications are not guaranteed—but similar work on circadian biology has already transformed understanding of shift work, jet lag, and seasonal affective disorder, pointing to future practical uses from a deeper grasp of how light shapes our daily biology.