Circadian rhythms and adequate sleep are essential to cognitive functioning. Pulses of blue light administered in the morning can re-entrain circadian rhythms and improve sleep difficulties. In a recent double-blind, placebo-controlled study of 32 adult patients (aged 18-48 years) with mild traumatic brain injury (mTBI), blue light was tested as a therapeutic approach to improving neurological recovery, brain connectivity, and cognitive performance. The effects of six weeks of daily 30-min pulses of blue light (peak ? = 469 nm) each morning versus amber placebo light (peak ? = 578 nm) were compared on neurocognitive and neuroimaging outcomes. These measures included gray matter volume (GMV), resting-state functional connectivity, directed connectivity using Granger causality, and white matter integrity using diffusion tensor imaging (DTI). Results suggest that blue light improved sleep timing, daytime sleepiness, and executive functioning. Relative to placebo, blue light was associated with increased volume of the posterior thalamus (i.e. pulvinar), greater thalamo-cortical functional connectivity, and increased axonal integrity of these pathways. The findings suggest that circadian rhythm and sleep mechanisms may play an important role in brain recovery after injury. Future research is needed, however these results suggest that the retinohypothalamic system may be a key target in facilitating brain injury recovery.
Killgore W et al. Neurobiol Dis. 2020;134:104679. Abstract
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