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
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.
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."
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
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