Effects of light exposure at night during development

- Aspects of the mammalian circadian system are functional from birth.
- The circadian system matures throughout the early postnatal period.
- Early lighting environment affects the maturation of the SCN and its outputs.
- Developmental light exposure alters SCN firing, clock genes, and DNA methylation.
- These changes shape adult circadian rhythms impacting physiology and behavior.

Disruption of the circadian system is increasingly prevalent in modern society. The mammalian circadian architecture is functional from birth and continues to develop throughout the early postnatal period. Importantly, light is the most salient entraining signal for the circadian system. Early life experiences can profoundly affect the developing brain, influencing adult behavior, health, and disease; thus, the immature circadian system may be particularly sensitive to circadian disruption. Indeed, early lighting environment impacts the maturation of the circadian system. The consequences of early light experience persist into adulthood influencing physiological and behavioral functions that are regulated by the circadian system. This review will discuss the development of the mammalian circadian system and implications of disruptive light exposure during early critical periods.