SEX-DEPENDENT MODULATION OF WHOLE BRAIN cFOS EXPRESSION BY LIGHT AND MELANOPSIN IN THE MOUSE.

Light is a fundamental feature of an animal's environment, signaling time of day, weather changes, approaching predators, and other survival cues. The extensive projections from the retina to the brain provide an anatomical substrate for light to adaptively tune circuit function based on changing environmental light. Yet we understand little about the scope and functional impact of light outside of visual and circadian circuits. To address this, we created a whole-brain atlas of light-induced cFos expression in the mouse brain. This approach yielded a strikingly broad pattern of light-driven cFos activation throughout the brain that extended beyond canonical visual circuits, with unexpectedly strong modulation of neuromodulatory centers. These patterns differed starkly in males and females, and were dependent primarily on melanopsin-expressing, intrinsically photosensitive retinal ganglion cells. These findings uncover surprising brainwide patterns of light modulation and are shared as an interactive resource so that they can inspire new, future studies.