Diagnostic imaging, neurology

MR brain imaging discovers blue light affects memory and alertness

12 December 2007

Researchers at the University of Liege, Belgium, and the University of Surrey, UK, have used functional magnetic resonance imaging (fMRI) to discover a previously unknown affect of light on the brain. They have shown that blue light can affect basic functions of the human brain such as alertness, memory, emotion and cognitive tasks.

Which colours of light are most effective and where in the brain these non-visual effects can be seen was previously not known. Now researchers at the Cyclotron Research Centre at the University of Liege and the Surrey Sleep Research Centre at the University of Surrey have ‘shed some novel light’ on these issues by using fMRI brain imaging while the participants were engaged on a working memory task.

In a research paper published in PLoS ONE (1) it is reported that the most effective light is blue light with a wavelength of 480 nm. This is in accordance with the hypothesis that such non-visual effects are mediated by a recently discovered ancient photoreceptor which is particularly sensitive to blue light.

More importantly maybe, by using very short exposures to light (< 1 minutes), in combination with brain imaging techniques, the researchers could identify the brain areas that are involved in the initial responses to this light. These included the brain stem and the thalamus. These areas are involved in the regulation of very basic aspects of brain function, such as the regulation of alertness and sleepiness.

Other areas that responded to light included the hippocampus and amygdala. These areas are well known to be involved in the regulation of higher functions such as memory and emotion.

In summary, the data establishes a brain basis for the wide ranging effects of light on how humans perform and feel. It has implications for the development of better artificial light environments and a better understanding of the effects of light on the human brain in general.

Dr Gilles Vandewalle, lead author, said, "It was impressive to see how only a minor difference in wavelength could have such a dramatically different effect on our fMRI results".

Dr Pierre Maquet co-senior author, commented, "As a neurologist I am impressed by the wide ranging effects of light on brain function and the range of brain areas that are affected. This is an area that certainly warrants further investigation."

Dr Derk-Jan Dijk, co-senior author said, "Humans are day-active animals, and maybe it is after all not so surprising to a biologist that blue light has these profound effects on our brain. After all, natural daylight contains quite a bit of blue light. We had simply forgotten about it because we are so preoccupied by the ‘visual’ effects of light, which are not particularly dependent on blue light. We now know that other aspects of brain function are."


1. Vandewalle G, Schmidt C, Albouy G, Sterpenich V, Darsaud A,  Rauchs G, Berken P-Y, Balteau E, Degueldre C, Luxen A, Maquet P, Dijk DJ. Brain Responses to Violet, Blue, and Green Monochromatic Light Exposures in Humans: Prominent Role of Blue Light and the Brainstem. PLoS ONE, issue 11/28 2007. The article is available at www.plosone.org

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