0070 The Effects of Acute Blue Wavelength Light Exposure on Functional Brain Connectivity and Mood

Abstract

Introduction: Blue wavelength light is an effective treatment for delayed sleep phase syndrome, seasonal affective disorder and bipolar depression. The role of blue light in regulating melatonin production has been extensively studied, but other potential neurophysiological effects remain poorly understood. Some studies have suggested that daily blue light exposure may modulate functional brain responses within the amygdala and prefrontal cortex (PFC), potentially explaining blue light's antidepressant effect. In this study we investigated the effects of a single 30‐minute session of blue light exposure on functional resting state connectivity between the amygdala and PFC. Methods: Twenty‐nine healthy 18‐32 year olds were randomly assigned to either receive 30 minutes of blue (n=17) or non‐blue (amber) light (n=12) exposure followed by a 7‐minute resting state scan. Pre‐ and post light exposure, participants completed the Positive and Negative Affect Scale, as a measure of state affect. Results: Individuals who received blue versus amber light showed greater positive connectivity between the right amygdala and the left dorsolateral prefrontal cortex (DLPFC) (x=‐24, y=46, z=18, k=90, volume p‐FDR corrected, p<0.001). Increased amygdala‐ DLFC connectivity correlated with greater decreases in negative mood for the blue (ρ=‐.55, p=0.03), but not the amber group. Using Granger Causality, we found that the directionality of information flow between these two areas was bidirectional (p<0.0025). Conclusion: Blue light exposure appears to facilitate greater information flow between the amygdala and the DLPFC at rest, potentially enhancing cognitive processes that regulate arousal and mood. As blue light exposure has been shown to enhance attention and learning, using blue light exposure during practice of emotional regulation strategies, such as reappraisal, may further increase the beneficial effects of blue light on mood. In order to use blue light exposure in a more targeted manner for sleep and mood disorders, further research into the underlying neurophysiological mechanisms is needed.