Let there be 'circadian' light

Researchers at UW Medicine have decoded what makes good lighting – lighting capable of stimulating the cone photoreceptor inputs to specific neurons in the eye that regulate circadian rhythms.

Their study, “A color vision circuit for non-image-forming vision in the primate retina,” published in Current Biology Feb. 20, identifies a cell in the retina, which plays an important role in signaling our brain centers that regulate circadian rhythms, boost alertness, help memory and cognitive function, and elevate mood.

These effects have been attributed to a pigment in the eye called melanopsin, which is sensitive to blue light, but researchers say cone photoreceptors are a thousand times more sensitive to light than melanopsin. The cone photoreceptor inputs to the circadian circuity respond to short wavelength blue light, but they also respond strongly to long wavelength oranges and yellows and contrasting light – the colors at sunrise and sunset.