Cognitive Enhancement by Transcranial Photobiomodulation Is Associated With Cerebrovascular Oxygenation of the Prefrontal Cortex

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.

Transcranial laser stimulation: Mitochondrial and cerebrovascular effects in younger and older healthy adults

“…The reliability of our bbNIRS method was first shown by Wang et al, 2017 [8] and then by the replication study of Pruitt et al, 2020 [6] in young and elderly participants. We have also shown the hemodynamic increases in [HbO] after TILS during two cognitive tasks (psychomotor vigilance task and delayed match to sample task) in Holmes et al, 2019 [5]. Kolyva et al, 2012 [37] have also previously shown increase on D…”

“…Since neurons are critically dependent on oxygen metabolism, TILS actions on CCO and hemoglobin oxygenation lead to multiple beneficial effects [3,10]. These effects include more efficient oxygen consumption for bioenergetics [2,3], resulting in enhanced PFC-based cognitive functions such as attention and working memory [5,11,12], executive function [13], and rule-based category learning [14].…”

“…CCO plays key roles in mitochondrial respiration, by catalyzing the reduction of oxygen to water and enabling adenosine triphosphate (ATP) production [19], and in hemodynamics, by catalyzing the synthesis of the vasodilator nitric oxide (NO) under low oxygen conditions [20]. TILS of the PFC augments CCO affinity for oxygen, increasing cerebral oxygen consumption, ATP production, NO release and cerebrovascular oxygenation, which facilitate neurocognitive functions [5,10,16,19].…”

“…Photodetectors are used to measure the light that is scattered and returned to the surface of the head. Fewer photons detected from a particular spectrum of wavelengths indicate a greater concentration of the chromophore with an absorption spectrum at those wavelengths [5].…”

Caffeine Effect on Cognitive Function during a Stroop Task: fNIRS Study

“…fNIRS is an inexpensive, relatively portable, and tolerant of motion artifacts neuroimaging method compare with other measurements which is completely noninvasive and could be used in daily life [ 22 , 30 ]. The fNIRS is widely employed to investigate human cognition [ 31 – 33 ]. The frontal areas of the brain, specifically the prefrontal cortex (PFC), are associated with cognition [ 34 – 36 ].…”