Photoreception for human circadian and neurobehavioral regulation

Abstract

Two convergent developments are transforming architectural lighting: (1) the advance of solid state lighting technologies and (2) the confirmation that light regulates human circadian, neuroendocrine, and neurobehavioral physiology, thereby influencing health and well-being. Analytic action spectra studies have shown peak sensitivity in the short-wavelength portion of the visible spectrum from 447 to 484 nm for the biological and behavioral effects of light in humans and other mammalian species. These studies led to the discovery of intrinsically photosensitive retinal ganglion cells (ipRGCs) that contain a photopigment named melanopsin. The ipRGCs interconnect with the classical visual rod and cone photoreceptors. Together, all retinal photoreceptors provide input to the retinohypothalamic tract (RHT). The RHT transmits information about environ mental light to the central circadian pacemaker as well as many other nonvisual centers in the nervous system. This chapter reviews the fundamental neurophysiology, the clinical and nonclinical therapeutic uses of light, as well as selected examples of published data on the effects of solid state light on human biology and behavior. Both the basic and applied science related to these discov eries are in a nascent stage. As new lighting technologies and applications are developed with the intent to improve human health and well-being, empirical evidence is critically needed to ensure the safety and efficacy of these advances. Collaboration between scientists and engineers across the fields of physics, biomedicine, lighting, and architecture will guide the best use of light for the benefit of humanity.