Vandewalle (2013): blue light affects visually blind

PDF: Vandewalle_JCN_xx_1-14_2013_blind-blue-light.pdf

Light regulates multiple non-image-forming (or nonvisual)
circadian, neuroendocrine, and neurobehavioral functions, via
outputs from intrinsically photosensitive retinal ganglion cells
(ipRGCs). Exposure to light directly enhances alertness and performance,
so light is an important regulator of wakefulness and
cognition. The roles of rods, cones, and ipRGCs in the impact of
light on cognitive brain functions remain unclear, however. A
small percentage of blind individuals retain non-image-forming
photoreception and offer a unique opportunity to investigate
light impacts in the absence of conscious vision, presumably
through ipRGCs. Here, we show that three such patients were
able to choose nonrandomly about the presence of light despite
their complete lack of sight. Furthermore, 2 sec of blue
light modified EEG activity when administered simultaneously
to auditory stimulations. fMRI further showed that, during an
auditory working memory task, less than a minute of blue light
triggered the recruitment of supplemental prefrontal and thalamic
brain regions involved in alertness and cognition regulation
as well as key areas of the default mode network. These
results, which have to be considered as a proof of concept, show
that non-image-forming photoreception triggers some awareness
for light and can have a more rapid impact on human cognition
than previously understood, if brain processing is actively
engaged. Furthermore, light stimulates higher cognitive brain
activity, independently of vision, and engages supplemental
brain areas to perform an ongoing cognitive process. To our
knowledge, our results constitute the first indication that ipRGC
signaling may rapidly affect fundamental cerebral organization,
so that it could potentially participate to the regulation of numerous
aspects of human brain function.

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