Blue-Light Therapy following Mild Traumatic Brain Injury: Effects on White Matter Water Diffusion in the Brain

Abstract

Mild traumatic brain injury (mTBI) is a common and often inconspicuous wound that is frequently associated with chronic low-grade symptoms and cognitive dysfunction. Previous evidence suggests that daily blue wavelength light therapy may be effective at reducing fatigue and improving sleep in patients recovering from mTBI. However, the effects of light therapy on recovering brain structure remain unexplored. In this study, we analyzed white matter diffusion properties, including generalized fractional anisotropy, and the quantity of water diffusion in isotropic (i.e., isotropic diffusion) and anisotropic fashion (i.e., quantitative anisotropy, QA) for fibers crossing 11 brain areas known to be significantly affected following mTBI. Specifically, we investigated how 6 weeks of daily morning blue light exposure therapy (compared to an amber-light placebo condition) impacted changes in white matter diffusion in individuals with mTBI. We observed a significant impact of the blue light treatment (relative to the placebo) on the amount of water diffusion (QA) for multiple brain areas, including the corpus callosum, anterior corona radiata, and thalamus. Moreover, many of these changes were associated with improvements in sleep latency and delayed memory. These findings suggest that blue wavelength light exposure may serve as one of the potential non-pharmacological treatments for facilitating structural and functional recovery following mTBI; they also support the use of QA as a reliable neuro-biomarker for mTBI therapies.

Daily Morning Blue Light Therapy for Post-mTBI Sleep Disruption: Effects on Brain Structure and Function

“…These studies took place in Boston, MA (study 1; n = 31) and Tucson, AZ (study 2; n = 31). Data on these two samples have been reported previously for individual samples ( 43 , 44 , 49 ), but the findings reported here are novel and have not been previously presented. Inclusion and exclusion criteria were the same across both studies and have been described elsewhere ( 43 , 44 , 50 ).…”

“…Across both trials, BLT was associated with reduced self-reported daytime sleepiness at the end of six of weeks of treatment ( 43 , 44 ); a circadian phase advance and increased midday sleep onset latency ( 43 ); and improved actigraphically-measured nighttime sleep quality ( 44 ). Neuroimaging evidence from the first trial indicated that BLT was associated with increases in bilateral thalamic volume, particularly in the pulvinar region ( 43 ); improved functional and structural connectivity between the thalamus and areas of the parietal cortex ( 43 ); and altered white matter diffusion characteristics in white matter tracts passing the through the thalamus, corpus callosum, and left anterior corona radiata ( 43 , 49 ). These neuroimaging findings suggest that altered brain structure and function in regions and circuits subserving alertness, attention, and cognitive control may be facilitated by improved nighttime sleep and reduced daytime sleepiness.…”

Prediction of Motor Recovery in Patients with Basal Ganglia Hemorrhage Using Diffusion Tensor Imaging

“…Essentially the main parameter that is measured in DTI is the degree of fractional anisotropy (FA) in a given voxel of the precessing proton and its Eigen vector in an ellipsoid domain [11]. Recently, new diffusion measures-quantitative anisotropy (QA)-have been introduced to the field of DTI for the analysis of diffusion properties of white matter [13,14]. QA represent how much water diffuses (i.e., density) in a specific/restricted direction and in an isotropic fashion (i.e., total isotropic component), respectively.…”

Development and Characterization of An Injury-free Model of Functional Pain in Rats by Exposure to Red Light

“…For example, blue light has been associated with sleep and metabolic regulations 10,15,48 ; light therapy has been used to control depression 20,26 , while bright light improved the mood of adolescents taking antidepressants compared to those without light therapy 57 . Kilgore and colleagues also reported that blue light modulated the activation of the anterior cingulate gyrus, may facilitate structural and functional recovery following mild traumatic brain injury, and may improve memory functions in humans 1,2,4 . Recently, a study comparing the treatment of actinic keratosis (AK) using red vs green light demonstrated that while both red and green light managed AK, green light exposure resulted in significantly less pain than red 61 .…”