Abstract
Transcranial infrared laser stimulation (TILS) is a novel, safe, non-invasive method of brain photobiomodulation. Laser stimulation of the human prefrontal cortex causes cognitive enhancement. To investigate the hemodynamic effects in prefrontal cortex by which this cognitive enhancement occurs, we used functional near-infrared spectroscopy (fNIRS), which is a safe, non-invasive method of monitoring hemodynamics. We measured concentration changes in oxygenated and deoxygenated hemoglobin, total hemoglobin and differential effects in 18 healthy adults during sustained attention and working memory performance, before and after laser of the right prefrontal cortex. We also measured 16 sham controls without photobiomodulation. fNIRS revealed large effects on prefrontal oxygenation during cognitive enhancement post-laser and provided the first demonstration that cognitive enhancement by transcranial photobiomodulation is associated with cerebrovascular oxygenation of the prefrontal cortex. Sham control data served to rule out that the laser effects were due to pre-post task repetition or other non-specific effects. A laser-fNIRS combination may be useful to stimulate and monitor cerebrovascular oxygenation associated with neurocognitive enhancement in healthy individuals and in those with prefrontal hypometabolism, such as in cognitive aging, dementia and many neuropsychiatric disorders.
Highlights
Photobiomodulation techniques using lasers or LEDs in the far-red to near-infrared spectrum, called low-level light/laser therapy, have been widely used for wound healing, musculoskeletal pain, arthritis, and other conditions (Brosseau et al, 2004; Hopkins et al, 2004; Cotler et al, 2015)
This experiment attempted to elucidate the hemodynamic effects of transcranial infrared laser stimulation (TILS) of the human prefrontal cortex at the wavelength, energy and power density used in previous cognitive augmentation studies
Average performance in the delayed matchto-sample task (DMS) improved after TILS, with significant improvements in both number of correct answers and memory retrieval time as assessed by paired t-tests
Summary
Photobiomodulation techniques using lasers or LEDs in the far-red to near-infrared spectrum, called low-level light/laser therapy, have been widely used for wound healing, musculoskeletal pain, arthritis, and other conditions (Brosseau et al, 2004; Hopkins et al, 2004; Cotler et al, 2015). Transcranial infrared laser stimulation (TILS) by 1064-nm laser has Transcranial Photobiomodulation Augments Cerebrovascular Oxygenation been introduced as a possible means of human cognitive enhancement (Barrett and Gonzalez-Lima, 2013; Gonzalez-Lima and Barrett, 2014; Hwang et al, 2016; Blanco et al, 2017a,b). This experiment attempted to elucidate the hemodynamic effects of TILS of the human prefrontal cortex at the wavelength, energy and power density used in previous cognitive augmentation studies. A better understanding of the hemodynamic effects of this new method for cognitive enhancement may allow progress toward its use as a clinical treatment
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