Night Light Color Could Be Attitude Adjuster
Scientific American, October 28, 2013
Nocturnal Light Exposure Impairs Affective Responses in a Wavelength-Dependent Manner
The Journal of Neuroscience, 7 August 2013, 33(32): 13081-13087
Tracy A. Bedrosian, et al.
Life on earth is entrained to a 24 h solar cycle that synchronizes circadian rhythms in physiology and behavior;
light is the most potent entraining cue.
In mammals, light is detected by (1) rods and cones, which mediate visual function, and
(2) intrinsically photosensitive retinal ganglion cells (ipRGCs), which primarily project to the suprachiasmatic nucleus (SCN) in the hypothalamus to regulate circadian rhythms.
ipRGCs also project to limbic brain regions, suggesting that, through this pathway, light may have a role in cognition and mood. Therefore, unnatural exposure to light may have negative consequences for mood or behavior.
Modern environmental lighting conditions have led to excessive exposure to light at night (LAN), and particularly to blue wavelength lights.
We hypothesized that nocturnal light exposure (i.e., dim LAN) would induce depressive responses and alter neuronal structure in hamsters (Phodopus sungorus).
If this effect is mediated by ipRGCs, which have reduced sensitivity to red wavelength light, then we predicted that red LAN would have limited effects on brain and behavior compared with shorter wavelengths.
Additionally, red LAN would not induce c-Fos activation in the SCN.
Our results demonstrate that exposure to LAN influences behavior and neuronal plasticity and that this effect is likely mediated by ipRGCs.
Modern sources of LAN that contain blue wavelengths may be particularly disruptive to the circadian system, potentially contributing to altered mood regulation.
What’s Keeping You Awake at Night?
Scitable. by Nature Education. June 07, 2013
effects of LED backlit screens and their emission of a certain blue-light wavelength on melatonin levels, an essential hormone that makes you drowsy and kicks in your sleep cycle.
Melatonin is released naturally at the onset of darkness, preparing your body for rest, and then continuously throughout the night as part of your natural circadian rhythm – your body’s daily biological clock.
However, melatonin can be partially curbed by exposure to light, and the abnormally bright glow of backlit computer screens seems to be especially disruptive to its release.
Suppression of melatonin then has the opposite effects, increasing alertness and arousal, and even altering REM sleep patterns when you finally do nod off.