The science behind best lights to affect sleep, mood, and learning

What makes good lighting? Scientists have decoded the answer.

A new study from UW Medicine suggests that the lighting that stimulates the cone photoreceptor inputs to specific neurons in the eye that regulate circadian rhythms- can be said as good lighting.

Scientists identified a cell in the retina known as an inhibitory interneuron or amacrine cell, which plays an essential role in signaling our brain centers that regulate circadian rhythms, boost alertness, help memory, and cognitive function, and elevate mood.

Melanopsin-expressing, intrinsically photosensitive retinal ganglion cells (ipRGCs) synchronize our biological clocks with the external light/dark cycle. Melanopsin is sensitive to blue light. But, scientists found that cone photoreceptors are a thousand times more sensitive to light as compared to melanopsin.

The cone photoreceptor inputs to the circadian circuity respond to short-wavelength blue light. Still, they also respond strongly to long-wavelength oranges and yellows and different light—the colors at sunrise and sunset.

Lead author Sara Patterson, a graduate student in neuroscience at the University of Washington School of Medicine, said how we set our internal clocks to the external light-dark cycle has been studied a lot. But how the changes in the color of light affect our brain has not.

“Color vision used for something other than color perception was the most exciting part for me.”

“So little is known about rare retinal circuitry that it was possible to find a new blue cone cell. She said there is a lot more to be discovered about how blue cone cells are projecting to other areas of the brain.”

Corresponding author Jay Neitz, professor of ophthalmology at the UW School of Medicine, a scientist at the UW Medicine Eye Institute, and a well-known color vision researcher said, “While sunrise light, blue light, and seasonal affective disorder (SAD) light have all tried to capture benefits of natural light, they haven’t been that effective because they are missing key science data. The science behind SAD light, for example, is to make light hundreds of times brighter than normal light to stimulate melanopsin.”

“This research all started because of our interest in the health benefits of having a natural light that occurs at the right time of day that helps regulate our circadian clock and our mood and alertness.”

The study is published in the journal Current Biology.

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