Exposure to Blue Light Increases Subsequent Functional Activation of the Prefrontal Cortex During Performance of a Working Memory Task

Abstract

This is the first study to suggest that a relatively brief, single exposure to blue light has a subsequent beneficial effect on working memory performance, even after cessation of exposure, and leads to temporarily persisting functional brain changes within prefrontal brain regions associated with executive functions. These findings may have broader implication for using blue-enriched light in a variety of work settings where alertness and quick decision-making are important.

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

“…The light exposure protocol is described in detail in Alkozei et al (2016) [ 10 ]. In brief, all participants began with a half-hour blue light Washout Period (described in more detail under Procedure) that involved sitting in a dark room while only exposed to two amber light devices (described below) mounted on a desk at a distance of approximately 80 cm from the participant’s nasion, with each light centered at a 45 degree angle from midline (see Fig 1A ).…”

“…Blue light exposure (or bright light more generally) at night leads to increases in subjectively and objectively measured alertness and vigilance, likely as a consequence of suppression of melatonin production [ 7 – 9 ]. However, studies have also shown that blue light (or blue-enriched white light) exposure during the day, a time when melatonin levels are naturally low, also leads to an increase in alertness and vigilance, as well as improvements in working memory performance [ 10 – 12 ]. For example, we have recently shown that 30 minutes of exposure to blue versus amber (placebo) wavelength light during the day led to subsequently faster performance on a working memory task (i.e., 45 minutes after light exposure) and increased functional brain responses in regions that are important for working memory processes, such as the dorsolateral and ventrolateral prefrontal cortex (DLPFC and VLPFC) [ 10 ].…”

“…However, studies have also shown that blue light (or blue-enriched white light) exposure during the day, a time when melatonin levels are naturally low, also leads to an increase in alertness and vigilance, as well as improvements in working memory performance [ 10 – 12 ]. For example, we have recently shown that 30 minutes of exposure to blue versus amber (placebo) wavelength light during the day led to subsequently faster performance on a working memory task (i.e., 45 minutes after light exposure) and increased functional brain responses in regions that are important for working memory processes, such as the dorsolateral and ventrolateral prefrontal cortex (DLPFC and VLPFC) [ 10 ]. This alerting effect has even been demonstrated in visually blind individuals, further suggesting that it is produced by activation of the non-image forming ipRGCs [ 13 ].…”

“…This alerting effect has even been demonstrated in visually blind individuals, further suggesting that it is produced by activation of the non-image forming ipRGCs [ 13 ]. The mechanisms underlying this alerting effect remain to be fully elucidated but one potential explanation that has been proposed as a result of these findings involves the potential stimulating effect of blue light on the LC, leading to increased noradrenergic activation within other areas of the brain (i.e., the PFC), resulting in increased alertness and speed of responding [ 4 , 10 ].…”

Long-term reduction of short wavelength light affects sustained attention and visuospatial working memory

“…The modulations were detected also in the cortex, in areas involved in bottom-up reorientation of attention and in the regions linked with top-down regulation of attention. At the behavioral level, blue enriched light was shown to enhance subjective alertness and led to significantly faster reaction times in tasks associated with sustained attention and working memory (Alkozei et al, 2016;Chellappa et al, 2011a). Our experimental condition is opposite, as we reduce blue light exposure and so are our results as we observe increasing reaction times and decreasing accuracy.…”