The changing brightness of sunlight during dawn and dusk is known to adjust circadian rhythms, but researchers now show that the shifting colour of the light does the same thing in mice.
Timothy Brown, Robert Lucas and their co-workers at the University of Manchester, UK, studied mice that were genetically engineered so researchers could stimulate the two colour-detecting pigments in the mouse retina one at a time. When they recorded the firing of neurons in the brain's clock centre, they found that this activity was in sync with changes in the colour of light between blue and yellow.
Mice exposed to lighting conditions that mimic twilight, including colour changes, showed differences in the timing of their daily body-temperature fluctuations, compared with animals exposed to light that shifted only in brightness. The authors suggest that the mammalian circadian clock uses colour to gauge the Sun's position during twilight.
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Colour tunes the body clock. Nature 520, 589 (2015). https://doi.org/10.1038/520589c
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DOI: https://doi.org/10.1038/520589c
