There is some divergence of opinion here. The Valkee people use blue / white light because they’re following a “sunlight substitution” model. The Vielight crowd, with their nasal torch and parietal-lobe headset, prefer near-infrared light.
The reasoning for infra-red cerebral stimulation is roughly as follows: Evolution has found it convenient to use heme groups (and more generally, porphyrin rings complexed around a metal atom) in many components of cell biology, because they are a convenient way to hold a spare electron until it’s needed in Redox chemistry. Hence the Cytochromes, and cytochrome oxidase, as well as hemoglobin and myoglobin. But that whole ‘conjugated ring, delocalised electron’ feature of porphyrins means that they also absorb near-IR wavelengths. Therefore (and here I am skipping some steps in the argument), cytochromes and COX need near-IR stimulation to function properly, and your brain will work better under bright illumination. Which is why Evolution gave me a bald spot.
No-one has followed the obvious corollary of treating heart attacks by threading a light-fibre catheter up through the veins into the heart and flooding the cardiac interior with bright lights.
