Exposure to Blue Wavelength Light Is Associated With Increases in Bidirectional Amygdala-DLPFC Connectivity at Rest

Blue wavelength light has been used successfully as a treatment method for certain mood disorders, but, the underlying mechanisms behind the mood enhancing effects of light remain poorly understood. We investigated the effects of a single dose of 30 min of blue wavelength light (n = 17) vs. amber wavelength light (n = 12) exposure in a sample of healthy adults on subsequent resting-state functional and directed connectivity, and associations with changes in state affect. Individuals who received blue vs. amber wavelength light showed greater positive connectivity between the right amygdala and a region within the left dorsolateral prefrontal cortex (DLPFC). In addition, using granger causality, the findings showed that individuals who received blue wavelength light displayed greater bidirectional information flow between these two regions relative to amber light. Furthermore, the strength of amygdala-DLPFC functional connectivity was associated with greater decreases in negative mood for the blue, but not the amber light condition. Blue light exposure may positively influence mood by modulating greater information flow between the amygdala and the DLPFC, which may result in greater engagement of cognitive control strategies that are needed to perceive and regulate arousal and mood. © Copyright © 2021 Alkozei, Dailey, Bajaj, Vanuk, Raikes and Killgore.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Acute exposure to blue wavelength light during memory consolidation improves verbal memory performance

Acute exposure to light within the blue wavelengths has been shown to enhance alertness and vigilance, and lead to improved speed on reaction time tasks, possibly due to activation of the noradrenergic system. It remains unclear, however, whether the effects of blue light extend beyond simple alertness processes to also enhance other aspects of cognition, such as memory performance. The aim of this study was to investigate the effects of a thirty minute pulse of blue light versus placebo (amber light) exposure in healthy normally rested individuals in the morning during verbal memory consolidation (i.e., 1.5 hours after memory acquisition) using an abbreviated version of the California Verbal Learning Test (CVLT-II). At delayed recall, individuals who received blue light (n = 12) during the consolidation period showed significantly better long-delay verbal recall than individuals who received amber light exposure (n = 18), while controlling for the effects of general intelligence, depressive symptoms and habitual wake time. These findings extend previous work demonstrating the effect of blue light on brain activation and alertness to further demonstrate its effectiveness at facilitating better memory consolidation and subsequent retention of verbal material. Although preliminary, these findings point to a potential application of blue wavelength light to optimize memory performance in healthy populations. It remains to be determined whether blue light exposure may also enhance performance in clinical populations with memory deficits

Development and Characterization of An Injury-free Model of Functional Pain in Rats by Exposure to Red Light

We report the development and characterization of a novel, injury-free rat model in which nociceptive sensitization after red light is observed in multiple body areas reminiscent of widespread pain in functional pain syndromes. Rats were exposed to red light-emitting diodes (RLED) (LEDs, 660 nm) at an intensity of 50 Lux for 8 hours daily for 5 days resulting in time- and dose-dependent thermal hyperalgesia and mechanical allodynia in both male and female rats. Females showed an earlier onset of mechanical allodynia than males. The pronociceptive effects of RLED were mediated through the visual system. RLED-induced thermal hyperalgesia and mechanical allodynia were reversed with medications commonly used for widespread pain, including gabapentin, tricyclic antidepressants, serotonin/norepinephrine reuptake inhibitors, and nonsteroidal anti-inflammatory drugs. Acetaminophen failed to reverse the RLED induced hypersensitivity. The hyperalgesic effects of RLED were blocked when bicuculline, a gamma-aminobutyric acid-A receptor antagonist, was administered into the rostra! ventromedial medulla, suggesting a role for increased descending facilitation in the pain pathway. Key experiments were subjected to a replication study with randomization, investigator blinding, inclusion of all data, and high levels of statistical rigor. RLED-induced thermal hyperalgesia and mechanical allodynia without injury offers a novel injury-free rodent model useful for the study of functional pain syndromes with widespread pain. RLED exposure also emphasizes the different biological effects of different colors of light exposure. Perspective: This study demonstrates the effect of light exposure on nociceptive thresholds. These biological effects of red LED add evidence to the emerging understanding of the biological effects of light of different colors in animals and humans. Understanding the underlying biology of red light-induced widespread pain may offer insights into functional pain states. (C) 2019 by the American Pain SocietyNational Center for Complementary and Alternative Health [R01AT009716]; National Institute for Neurological Disorders and StrokeUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Neurological Disorders & Stroke (NINDS) [1R01N5098772]; NINDSUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Neurological Disorders & Stroke (NINDS); Children's Tumor Foundation; University of Arizona12 month embargo; published online: 2 May 2019This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]