Light-sensitive brain pathways and aging

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.

Melatonin suppression and sleepiness in children exposed to blue‐enriched white LED lighting at night

“…The results of those studies are closely related to the high photosensitivity of melatonin-containing retinal ganglion cells (mRGCs) to blue light. It is now well established that the retinohypothalamic inputs of photic signals from mRGCs into various brain areas (Daneault et al 2016) greatly contribute to non-image forming responses such as circadian photoentrainment and light-induced melatonin suppression. Coincidently, the age-related increase in lens absorbance becomes remarkable particularly for the short wavelength range, suggesting that the difference between melatonin sensitivity in children and that in adults is more apparent under a high color temperature lighting condition than under a low color temperature lighting condition.…”

Investigation of an Immediate Effect of Bright Light on Oxygen Consumption, Heart Rate, Cortisol, and α-Amylase in Seasonal Affective Disorder Subjects and Healthy Controls

“…As a comparator, red light was used (it does not trigger melanopsin photoreception, largely mediating the nonvisual physiological effects of light [reviewed in [17]]). It was hypothesized that metabolism (as characterized by oxygen consumption, heart rate, cortisol, and α-amylase values) will be increased rapidly following exposure to bright white light (vs. red light) in both the SAD and non-SAD, with the effect probably being more significant in the SAD group.…”

Color Glasses during Morning Drive for Commuting-Effects on Autonomic Functions, Alertness, and Nocturnal Sleep

“…Respiration frequency may be controlled by the inputs from both chemoreceptors and baroreceptors and by the psychological factors. Furthermore, the biological effects of blue light could be mediated by non-image forming visual functions which involves intrinsically photosensitive retinal ganglion cells [1], [3], [4], [13], [14]. Blue light is also known to enhance alertness at least immediately after exposure [6].…”