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J Physiol Anthropol. 2016 Mar 15;35:9. doi: 10.1186/s40101-016-0091-9.

Light-sensitive brain pathways and aging.

Author information

1
Functional Neuroimaging Unit, University of Montreal Geriatric Institute, Montreal, QC, Canada. veronique.daneault@gmail.com.
2
Center for Advanced Research in Sleep Medicine, Hôpital du Sacré-Cœur de Montréal, Montreal, QC, Canada. veronique.daneault@gmail.com.
3
Department of Psychology, University of Montreal, Montreal, QC, Canada. veronique.daneault@gmail.com.
4
Center for Advanced Research in Sleep Medicine, Hôpital du Sacré-Cœur de Montréal, Montreal, QC, Canada.
5
Functional Neuroimaging Unit, University of Montreal Geriatric Institute, Montreal, QC, Canada.
6
Department of Psychology, University of Montreal, Montreal, QC, Canada.
7
Cyclotron Research Centre, University of Liège, Liège, Belgium.

Abstract

Notwithstanding its effects on the classical visual system allowing image formation, light acts upon several non-image-forming (NIF) functions including body temperature, hormonal secretions, sleep-wake cycle, alertness, and cognitive performance. Studies have shown that NIF functions are maximally sensitive to blue wavelengths (460-480 nm), in comparison to longer light wavelengths. Higher blue light sensitivity has been reported for melatonin suppression, pupillary constriction, vigilance, and performance improvement but also for modulation of cognitive brain functions. Studies investigating acute stimulating effects of light on brain activity during the execution of cognitive tasks have suggested that brain activations progress from subcortical regions involved in alertness, such as the thalamus, the hypothalamus, and the brainstem, before reaching cortical regions associated with the ongoing task. In the course of aging, lower blue light sensitivity of some NIF functions has been reported. Here, we first describe neural pathways underlying effects of light on NIF functions and we discuss eye and cerebral mechanisms associated with aging which may affect NIF light sensitivity. Thereafter, we report results of investigations on pupillary constriction and cognitive brain sensitivity to light in the course of aging. Whereas the impact of light on cognitive brain responses appears to decrease substantially, pupillary constriction seems to remain more intact over the lifespan. Altogether, these results demonstrate that aging research should take into account the diversity of the pathways underlying the effects of light on specific NIF functions which may explain their differences in light sensitivity.

KEYWORDS:

Aging; Brain; Light; Non-image-forming (NIF) functions

PMID:
26980095
PMCID:
PMC4791759
DOI:
10.1186/s40101-016-0091-9
[Indexed for MEDLINE]
Free PMC Article

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