Effects of blue light during and after exposure on auditory working memory.

Introduction: Exposure to short-wavelength light (i.e., blue light) has been shown to enhance cognitive function in humans. While most prior studies have focused on visuospatial working memory, the effects of blue light on auditory working memory, particularly tasks involving the phonological loop, remain underexplored. This study investigated both the during- and post-exposure effects of blue light on auditory memory performance.

Methods: Fifteen healthy university students (13 males, 2 females; 21.47 ± 1.06 years old) participated in a randomized crossover design. Each participant was exposed to three lighting conditions for approximately 20-min: blue (λ = 476 nm, illuminance = 21.84 lx, 13.8 log photons/s-1.cm-2, melanopic EDI = 169.68 lx), amber (λ = 580 nm, illuminance = 61.65 lx, 13.5 log photons/s-1.cm-2, melanopic EDI = 2.87 lx) and dim light (baseline; illuminance < 5.00 lx). Each session was separated by a one-week washout period. To mitigate order effects, the sequence of light conditions was randomized across participants. The modified version of the Sternberg working memory task was performed during light exposure and after a 10-min break (i.e., During- vs Post-exposure phase). The accuracy, reaction time, subject anxiety and subject sleepiness were measured.

Results: In the post-exposure phase, blue light significantly improved accuracy compared to amber (p < 0.01, d = 0.66) and dim light (p < 0.01, d = 0.67). No significant differences were observed during exposure or in reaction time across three light conditions. Anxiety levels were significantly higher during blue light exposure (vs. amber: p = 0.013, d = 0.96; vs. dim: p = 0.027, d = 0.83), while sleepiness remained unchanged.

Conclusions: Blue light exposure may enhance auditory working memory accuracy with a delayed effect, independent of vigilance or processing speed. While these findings are promising, the observed effects are preliminary and require validation in larger and more diverse populations.