Wavelength-dependent modulation of brain responses to a working memory task by daytime light exposure

Area of Science:

• Neuroscience
• Vision Science
• Cognitive Science

Background:

• Light influences nonvisual brain responses affecting physiology and behavior.
• Melanopsin-expressing ganglion cells are sensitive to blue light (470-480 nm), distinct from the green-light-sensitive photopic system.
• Evidence for blue light modulating nonvisual brain activity in complex cognitive tasks is lacking.

Purpose of the Study:

• To investigate the effects of monochromatic blue and green light exposure on brain activity during an auditory working memory task.
• To determine if blue light can modulate nonvisual brain responses related to cognitive function.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to measure brain responses.
• Participants performed an auditory working memory task during a short (18 min) daytime exposure to monochromatic blue (470 nm) or green (550 nm) light.
• Light intensity was controlled at 3 x 10(13) photons/cm2/s.

Main Results:

• Blue light exposure enhanced brain responses in frontal and parietal cortices, areas crucial for working memory.
• Green light exposure did not enhance, and sometimes decreased, brain responses compared to blue light.
• Blue light also affected the thalamus, which modulates cognition through arousal.

Conclusions:

• Monochromatic light exposure can rapidly influence cognitive functions.
• These rapid effects on cognition are likely mediated by the melanopsin-based photoreceptor system.
• Blue light holds potential for modulating cognitive performance through nonvisual pathways.