…Although light with longer wavelengths penetrates into the brain more effectively, shorter wavelength light can also penetrate into deep brain structures and regulate, for example, the seasonal cycle of reproduction in birds..,. Penetration of light into the brain has also been demonstrated in larger animals, including sheep and dog…

…light penetrating into the substantia nigra could be the source of oxidative stress. Light could oxidise dopamine and, in turn, induce the formation of neuromelanin, and cause dopamine neuron degeneration...

….animals continuously exposed to bright light for 3 months showed a significant decrease in dopamine (33%) and DOPAC (44%) ….

….the effect of light on dopamine neuron is strictly dependent on the wavelength used and the time of exposure….

…whether the reduction in TH-positive neurons produced by continuous exposure to light was induced by a direct effect of light on the substantia nigra or whether it was indirectly produced by the stress caused by retina activation (i.e. the complete alteration of the circadian rhythm). Continuous bright light profoundly alters the circadian cycle of the animals and their hormonal homeostasis…

One would suspect that the amount of light that reaches the substantia nigra in the human brain—for the size of the head, the thickness of the skull and the deep brain localization of the substantia nigra—will be negligible. However, scientific data refutes that assumption…. a tiny amount of light can reach deep brain structures in human beings and this amount is proportional to the length of exposure and the brightness of the light source….

…these observations suggest that artificial light rather than sunlight could play a role in Parkinson's disease,….

the spectral characteristics of artificial light, especially fluorescent light, are completely different from sunlight, as the sunlight spectrum is continuous while fluorescent light spectrum is discontinuous and shows several peaks. Light frequencies of the sunlight spectrum could protect rather than damage the dopamine neurons…

…the concept of plurifocal illness in Parkinson's disease is absolutely questionable since it is linked to the diagnostic purity….

AND THE FINAL PAGE OF THE STUDY SAYS:
Competing financial interests
The authors declare no competing financial interests.
Corresponding author
Correspondence to:
• Roberto Maggio
This work is licensed under a Creative Commons Attribution-Non-Commercial-NoDerivs 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/3.0/