A team of researchers from the University of Oxford (UK) has shown how different colors of light can affect our ability to sleep. To do this, the experts, led by Stuart Peirson, a scientist at the Oxford Neuroscientific Institute of Sleep, conducted various experiments with mice with light as the protagonist.
“When we exposed the mice to light overnight, they fell asleep. However, at the same time, their levels of corticosterone increased, a stress hormone produced by the adrenal gland that regulates the stress response and triggers arousal during wakefulness. We wanted to understand how these two effects were related and how they were linked to a blue light-sensitive pigment called melanopsin , which we know plays a key role in setting our biological clock, ”Peirson clarifies.
Light experiments
The team exposed the mice to three different colors of light: purple, blue and green . Experts expected the blue light to induce sleep faster; however, it was the green light that caused a rapid onset of sleep, between 1 and 3 minutes. The colors blue and light purple delayed sleep, with the following data: the onset of sleep occurred between 16 and 19 minutes for blue and between 5 and 10 minutes for purple.
“ The results show that mice exposed to blue light were less sleepy than those exposed to violet and green light . The effect was confirmed in mice using green and blue light at a time when they would generally be less active, ”says Peirson.
To investigate the role of melanopsin, the researchers carried out the same test in mice that lacked this protein. For these mice, surprisingly, the colors had opposite effects: blue caused a rapid onset of sleep, while green and violet significantly delayed sleep, showing that melanopsin is necessary for the wavelength effects of sleep. light on sleep.
“ This study shows that there are different pathways from the eye to the brain and melanopsin has a more complex role than previously thought, affecting both pathways. This is the first time that they have been shown to regulate adrenal stress responses, ”says Peirson.
The results of the work show how the colors of light have different effects on sleep or wakefulness, which helps us understand how the color of artificial light can affect our alertness and the stage of sleep.
The study has been published in the journal PloS Biology.
