Bright light stimulation was found to increase activity in brain areas related to processing of visual sensory information and tactile stimuli. The findings constitute the first ever published scientific article about functional modulation of the brain with bright light delivered to the brain through the ears.
"The research results confirm that it is possible to influence brain functions with bright light delivered directly to the brain through the ear," says researcher TuomoStarck from the Oulu University Hospital. "The group that received bright light demonstrated in the analysis significant increase in neural network activity especially in brain areas connected with visual perception."
The study was conducted with 51 healthy test subjects, utilizing functional magnetic resonance imaging (fMRI). Some of the test subjects were given bright light into the ear canals with an optical fibre, and for others the light source was switched off. The eyes of the test subjects were covered during the study so that they were unable to determine which group they belonged to. Optical fiber did not warm up from the influence of light.
The study setting was typical for brain imaging, and corresponds with a placebo controlled setting. Real time functions of the brain's resting state neural networks were measured in the study with fMRI, making it possible to locate the regions of the brain where the amount of blood and its oxygen saturation change as a result of intervention; in this case as a result of bright light.
"There is earlier proof of the existence of photosensitive proteins, such as opsins, in the brain. This study confirms light-responsiveness of the brain itself, and that bright light given through the ear canal is a very viable method for influencing mood," said Professor and Leading Senior Physician Timo Takala from Oulu Deaconess Institute.
According to a second, closely related research result by Oulu University researchers, presented in March at the European Congress of Psychiatry, the human brain contains large amounts of photosensitive OPN4 (melanopsin) receptor protein. The clinical efficacy of bright light therapy for mood disorders when administered through the eye is believed to be based on the photosensitive OPN4-protein that has earlier been found only on the retina.
"Discovery of the photosensitive OPN4-protein in several parts of the human brain adds to the body of evidence that bright light channeled to the brain directly - and not only through the eyes - increases the activity of brain functions," comments Chief Science Officer Juuso Nissila from the Finnish company Valkee Oy.
Bright light is widely recognized as an effective therapy for treating seasonal affective disorder. The Valkee bright light headset is based on the latest research findings regarding photosensitivity of the brain: bright light is channeled through the ear canal directly to those brain areas that are known to be central in depression, and that have been discovered in studies at the Oulu University to contain photosensitive proteins.
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