Understanding the Mechanisms of Blue Light Exposure on Cognitive Performance
Abstract
Broad spectrum light, also known as ?white light? (e.g., light emitted from the sun or most artificial light devices) comprises many different wavelengths that can be decomposed into the various colors of the spectrum. Studies have shown that acute exposure to light within the blue wavelengths (~460 nm) can lead to increases in alertness, better performance on cognitive tasks, improved mood, and corresponding functional brain activation changes during the day and at night. When blue light enters the retina, its signals are being transported via retinal ganglion cells to an area in hypothalamus, the suprachiasmatic nucleus (SCN). The SCN will then send signals to the pineal gland, which will suppress the production of the hormone melatonin. One of the reasons for the alerting effects of blue light is the suppression of melatonin production. Melatonin release precedes sleep onset and is released in a circadian fashion with peaks at night and generally low levels during the day. Blue light exposure has been identified as a trigger that signals the suppression of melatonin production. This will lead to reduction in sleepiness and increases in alertness, especially at night when melatonin levels are high. However, studies have also shown that blue light leads to increases in alertness and better performance on more complex cognitive functioning tasks during the day, when melatonin levels are very low, and has also been used as a treatment for seasonal and non-seasonal depression. It is therefore likely that blue light not only leads to a suppression of melatonin, but that it works via a second pathway that can explain the beneficial effects of blue light on cognitive functioning during the day as well as its positive effects on mood. The aim of this study is to understand and identify this second pathway. We are proposing that blue light also activates a small area in the brainstem, the locus coeruleus (LC), which when activated releases norepinephrine throughout the brain, leading to a number of changes in cognitive processes. The hypothalamus also has projections to the LC, which makes it likely that it transmits the signals it receives from the retina to the LC, which in turn increases the production of norepinephrine. Increased norepinephrine has been associated with better cognitive functioning and improvements in mood. However, no study has directly tested whether blue light leads to an increase in norepinephrine and how this may be associated with melatonin suppression, performance on cognitive and emotional tasks, and changes in subjective alertness and mood. The proposed study aims to identify the answers to these questions. In the proposed study, participants will be exposed to blue wavelength light during functional magnetic resonance imaging while completing cognitive and emotional tasks. Participants? pupil dilation will be continuously measured, as this has been shown to be an index of norepinephrine release and LC activity. Participants will also provide saliva samples at regular intervals to be analyzed for melatonin concentration. Participants? mood and subjective alertness will also be measured at regular intervals before, during, and after the light exposure. While in the scanner, participants will complete cognitive and emotional processing tasks before and after blue light exposure. Changes in norepinephrine release, melatonin concentration, subjective measures of alertness and mood, as well as changes in functional brain activation changes will be monitored and analyzed. Participants will complete the same procedure 1 week later when exposed to non-blue (amber) light at the same intensity to ensure that the effects are the result of blue light in particular. The order of the light color will be counterbalanced across participants and visits. The results of this study will be used to inform the best applications of blue light exposure in a large number of settings. Once it is know
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 05, 2019
- Source ID
- W81XWH1910074
Entities
People
- Anna Alkozei
Organizations
- United States Army
- University of Arizona