French scientists have found that orange lighting can be a stimulant of brain activity, which is associated with wakefulness and concentration. The work of scientists is published in the journal Proceedings of the National Academy of Sciences, and New Scientist writes briefly about it.

As part of a study of 16 participants, a memory test was performed by ear while their brain function was monitored using magnetic resonance imaging. Before testing, each of the volunteers was stimulated with the help of light from one of three wavelengths: green, blue and orange. After that, the volunteers were in complete darkness for 70 minutes, and then a test followed, during which the eyes of the subjects were irradiated with green light.

It turns out that preliminary stimulation with long-wavelength light can enhance brain activity in areas of the prefrontal cortex associated with concentration. The blue color suppressed such activity, and the green one had almost no effect on anything. The effect, called by scientists “light memory”, lasted much longer than necessary to restore pigment in rods and cones of the retina.

According to the authors, the revealed effect can be explained by the activity of photosensitive retinal ganglion cells (ipRGCs), discovered back in the early 90s of the twentieth century. These nerve cells are not interconnected with vision, but with the control of the biological rhythms of animals and humans. They contain the pigment melanopsin, which has two conformations: with a long-wavelength and a short-wavelength absorption maximum. The authors note, in general terms, the activity of orange light is that it regenerates melanopsin, which is responsible for biorhythms, and makes the retina much more sensitive to green light. However, the molecular mechanisms of this process are still not clear.