Daytime light exposure dynamically enhances brain responses.
In humans, light enhances both alertness and performance during nighttime and daytime [1-4] and influences regional brain function [5]. These effects do not correspond to classical visual responses but involve a non-image forming (NIF) system, which elicits greater endocrine, physiological, neurophysiological, and behavioral responses to shorter light wavelengths than to wavelengths geared toward the visual system [6-11]. During daytime, the neural changes induced by light exposure, and their time courses, are largely unknown. With functional magnetic resonance imaging (fMRI), we characterized the neural correlates of the alerting effect of daytime light by assessing the responses to an auditory oddball task [12-15], before and after a short exposure to a bright white light. Light-induced improvement in subjective alertness was linearly related to responses in the posterior thalamus. In addition, light enhanced responses in a set of cortical areas supporting attentional oddball effects, and it prevented decreases of activity otherwise observed during continuous darkness. Responses to light were remarkably dynamic. They declined within minutes after the end of the light stimulus, following various region-specific time courses. These findings suggest that light can modulate activity of subcortical structures involved in alertness, thereby dynamically promoting cortical activity in networks involved in ongoing nonvisual cognitive processes.
Vandewalle
Gilles
G
Cyclotron Research Center, University of Liège, Liège B-4000, Belgium.
Balteau
Evelyne
E
Phillips
Christophe
C
Degueldre
Christian
C
Moreau
Vincent
V
Sterpenich
Virginie
V
Albouy
Geneviève
G
Darsaud
Annabelle
A
Desseilles
Martin
M
Dang-Vu
Thien Thanh
TT
Peigneux
Philippe
P
Luxen
André
A
Dijk
Derk-Jan
DJ
Maquet
Pierre
P
D000161:Acoustic Stimulation; D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology / Q000528:radiation effects*; D001921:Brain / Q000502:physiology*; D003071:Cognition / Q000502:physiology / Q000528:radiation effects*; D006801:Humans; D008279:Magnetic Resonance Imaging; D010775:Photic Stimulation; D013472:Sunlight; D013997:Time Factors