Time, sleep and memory: How light affects our physiology and behaviour

Light exerts profound effects on our physiology and behaviour. This includes synchronising our internal biological clock to the external light/dark cycle, regulating sleep and arousal and even modulating our cognitive performance. In mammals, these effects are mediated via retinal photoreceptors. Work on the entrainment of circadian rhythms by light has led to the identification of a novel retinal photoreceptor system, consisting of a subset of photosensitive retinal ganglion cells (pRGCs) expressing the photopigment melanopsin. These cells project to a diverse range of central brain targets, mediating different non-visual responses to light. These cells are most sensitive to blue light, which has led to an increasing concern about the use of artificial light on a night, particularly from LED-based devices such as tablets and smartphones. Despite the remarkable public interest in this topic, the complexity of the melanopsin system is widely unappreciated. In this talk I will describe the discovery and physiology of this photoreceptor system, and our work on its involvement in the regulation of circadian rhythms, sleep and cognitive performance. I will end by discussing how we can avoid or take advantage of the non-visual effects of light in our daily lives.

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