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

Abstract

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.

Blue light exposure increases functional connectivity between dorsolateral prefrontal cortex and multiple cortical regions

“…geometric center) of each significantly correlated atlas-based ROI. As reported in our prior publication [5], blue light was associated with significantly greater connectivity between the DLPFC and right amygdala. However, as evident in Fig.…”

“…Exposure to bright light, especially in the blue wavelengths, leads to immediate improvements in mood [4,5], simple alertness [6], working memory [7], and retention of long-term verbal memory [8]. We recently demonstrated that a single 30-min exposure to blue-wavelength light (versus amber placebo light) was associated with a significant increase in subsequent functional connectivity between the right amygdala and a region of the left dorsolateral prefrontal cortex (DLPFC), within the horizontal section of the intermediate frontal sulcus (imfs-h) [9], a finding that was associated with acute declines in negative mood state [5]. Importantly, the connectivity between these two regions was bidirectional, suggesting that information flow was significant in both directions.…”

Treatment with morning blue light increases left amygdala volume and sleep duration among individuals with posttraumatic stress disorder

“…Together, these findings suggest that BLT plays an important role in normalizing amygdala volume in PTSD, perhaps via enhanced sleep, circadian alignment, or direct stimulation that affects amygdala responses. Recent findings suggest that light exposure suppresses acute responses within the amygdala but may increase the functional connectivity between the amygdala and prefrontal cortex ( Alkozei et al, 2021 ; Mcglashan et al, 2021 ; Killgore et al, 2022 ). Thus, repeated exposures to BLT may lead to altered patterns of activity within the amygdala that facilitate volumetric increases.…”

Investigating the relationship between background luminance and self-reported valence of auditory stimuli

“…The colour blue is known to induce a strong response from the ipRGCs (Berson et al, 2002;Gooley et al, 2012;McDougal & Gamlin, 2008). Some studies have also indicated that the ipRGCs processing is projected to brain regions relevant for emotional processing (Alkozei et al, 2021;Killgore et al, 2020;Vandewalle et al, 2007). For example, Alkozei et al (2021) suggested that blue light might enhance emotional experience by strengthening the bidirectional information flow between amygdala and left dorsolateral prefrontal cortex.…”

“…Some studies have also indicated that the ipRGCs processing is projected to brain regions relevant for emotional processing (Alkozei et al, 2021;Killgore et al, 2020;Vandewalle et al, 2007). For example, Alkozei et al (2021) suggested that blue light might enhance emotional experience by strengthening the bidirectional information flow between amygdala and left dorsolateral prefrontal cortex. Killgore et al (2020) also proposed that blue light enhanced emotional experience through the increased neural efficiency, as seen in reduced activation in the neural network for attention-demanding tasks (i.e., Task Positive Network/TPN).…”