Color—Not Just Light—May Affect Our Body Clock

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It’s well-known that our body responds to light and dark to help set its circadian rhythms. But new research suggests that our bodies may also respond to color in order to keep internal time.

A new study by researchers from the University of California, Santa Cruz,demonstrates that mice, at least, use the color of light to set their body clock. The researchers investigated whether color signals from the eyes wound up in the suprachiasmatic nucleus—the part of the brain in vertebrates that keeps time using electrical and chemical signals.


The team measured nerve signals in the suprachiasmatic as they exposed mice to different colors and intensities of light. They did that using a artificial sky that could create day or night by turning on or off—but could also be set up to change color, in the way we see during sunrise and sunset. It turned out that when the artificial sky provided color—with the oranges and blues associated with sunset—the mice behaved perfectly normally; without the color, their bodies became slightly confused and physiology, such as body temperature, lagged behind the usual way of things by around 30 minutes.

Interestingly, even in excised brain tissue the neurons in this part of the brain continue to fire. Subsequent analysis of the brain tissue in these mice confirmed that the neurons in the suprachiasmatic region of the brain were firing with a time lag, too. The results are published in PLOS Biology.


While the finding doesn’t translate directly to humans, the commonality between the suprachiasmatic region is strong between mammals. The researchers reckon that the knowledge that color influences the body clock could help make indoor lighting that better helps us transition between wake and sleep, say, or overcome jet-lag and seasonal affective disorder. [PLOS Biology via Science]

Image by Bill Gracey under Creative Commons license