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 colour 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 colour of light to set their body clock. The researchers investigated whether colour 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 colours 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 colour, in the way we see during sunrise and sunset. It turned out that when the artificial sky provided colour -- with the oranges and blues associated with sunset -- the mice behaved perfectly normally; without the colour, 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 colour 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]
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