Brain Responses Dynamically Enhanced By Daytime Light Exposu

Exposure to light is known to enhance both alertness and performance in humans, but little is understood regarding the neurological basis for these effects, especially those associated with daytime light exposure. Now, by exposing subjects to light and imaging their brains while they subsequently perform a cognitive test, researchers have begun to identify brain regions involved in the effects on brain function of daytime light exposure. The findings are reported by Gilles Vandewalle and Pierre Maquet of the University of Liege, Derk-Jan Dijk of the University of Surrey, and additional colleagues and appear in the August issue of the journal Current Biology, published by Cell Press.

Our brain does not use light only to form images of the world. Ambient light levels are detected by our nervous system and, without forming any image, profoundly influence our brain function and various aspects of our physiology, including circadian rhythms, hormone release, and heart rate. These responses are induced by a special non-image-forming (NIF) brain system, which researchers have begun to characterize in animal models. In human studies, much work has focused on the effects of nighttime light exposure, but little is known about daytime responses to light. Especially mysterious are the neural correlates of these responses, and their temporal dynamics. Such issues are of significant interest given that daytime sleepiness is a major source of complaint in modern society and has considerable socio-economic implications.

In the present study, the researchers showed that a brief (21-minute) morning exposure to a bright white light increases alertness and significantly boosts the brain's responses to an experimental test that requires attention only to sound. In a parallel neuroimaging analysis, this boost in alertness was found to correlate with responses in various areas of the brain, including regions of the cortex known to support performance on the auditory test. The regional brain changes were found to be highly dynamic, dissipating within a few minutes. These new findings therefore show that light exposure, even during the day, can quickly modulate regional brain function in areas involved in alertness and non-visual cognitive processes.

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The researchers include Gilles Vandewalle, Evelyne Balteau, Christophe Phillips, Christian Degueldre, Vincent Moreau, Virginie Sterpenich, Genevieve Albouy, Annabelle Darsaud, Philippe Peigneux, and Andre Luxen of University of Liege in Liege, Belgium; Martin Desseilles, Thien Thanh Dang-Vu, and Pierre Maquet of University of Liege in Liege, Belgium and Centre Hospitalier Universitaire in Liege, Belgium; Derk-Jan Dijk of University of Surrey in Guildford, UK.

The study was supported by the Belgian Fonds National de la Recherche Scientifique (FNRS), Fondation Medicale Reine Elisabeth (FMRE), University of Liege, PAI/IAP Interuniversity Pole of Attraction P5/04, and Wellcome Trust-GR069714MA (D.J.D). G.V., E.B., V.S., M.D., T.D.-V., and P.M. are supported by FNRS.

Vandewalle et al.: "Daytime Light Exposure Dynamically Enhances Brain Responses." Publishing in Current Biology 16, 1616 -1621, August 22, 2006 DOI 10.1016/j.cub.2006.06.031. http://www.current-biology.com/
Contact: Heidi Hardman
Cell Press
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Brain Responses Dynamically Enhanced By Daytime Light Exposu