Site-specific effects of 800- and 850-nm forehead transcranial photobiomodulation on prefrontal bilateral connectivity and unilateral coupling in young adults

Abstract

Transcranial photobiomodulation (tPBM) is a noninvasive neuromodulation method that facilitates the improvement of human cognition. However, limited information is available in the literature on the wavelength-and site-specific effects of prefrontal tPBM. Moreover, 2-channel broadband near-infrared spectroscopy (2-bbNIRS) is a new approach for quantifying infra-slow oscillations (ISO; 0.005 to 0.2 Hz) of neurophysiological networks in the resting human brain in vivo.Aim: We aim to prove the hypothesis that the hemodynamic and metabolic activities of the resting prefrontal cortex are significantly modulated by tPBM and that the modulation is wavelength-and site-specific in different ISO bands.Approach: Noninvasive 8-min tPBM with an 800-or 850-nm laser or sham was delivered to either side of the forehead of 26 healthy young adults. A 2-bbNIRS unit was used to record prefrontal ISO activity 7 min before and after tPBM/sham. The measured time series were analyzed in the frequency domain to determine the coherence of hemodynamic and metabolic activities at each of the three ISO frequency bands. Sham-controlled coherence values represent tPBM-induced effects on neurophysiological networks.Results: Prefrontal tPBM by either wavelength and on either lateral side of the forehead (1) increased ipsilateral metabolic-hemodynamic coupling in the endogenic band and (2) desynchronized bilateral activity of metabolism in the neurogenic band and vascular smooth-muscle hemodynamics in the myogenic band. Site-specific effects of laser tPBM were also observed with significant enhancement of bilateral hemodynamic and metabolic connectivity by the right prefrontal 800-nm tPBM.Conclusions: Prefrontal tPBM can significantly modulate neurophysiological networks bilaterally and coupling unilaterally in the human prefrontal cortex. Such modulation effects are site-and wavelength-specific for each ISO band.

Directed physiological networks in the human prefrontal cortex at rest and post transcranial photobiomodulation

“…Consequently, this signaling reaction boosts mitochondrial functions for human cognition in the normal brain and promotes energy supplementation in the disease-affected brain with prominent mitochondrial dysfunction 25 . Our group recently reported several noninvasive in vivo human studies to support the aforementioned mechanism of tPBM-induced excitation of mitochondrial CCO by showing signi cant increases in cerebral concentrations of redox state of cytochrome c oxidase (Δ[CCO]), oxygenated hemoglobin (Δ[HbO]), and total hemoglobin (Δ[HbT]) 10,[26][27][28] . However, studies on tPBM-stimulated electrophysiological responses in living human brains are limited, with only a few publications [29][30][31][32] .…”

“…Therefore, it is commonly used in clinical settings and research studies. EEG signals are often analyzed in ve frequency bands: delta (1-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), beta (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), and gamma (> 30 Hz). Different EEG frequency bands have shown distinct coupling with haemodynamic activity in NVC studies based on the brain regions of interest, tasks, and neurological diseases 4,5,[12][13][14][15] .…”

Unilateral Mitochondrial-Hemodynamic Coupling and Bilateral Connectivity in the Younger and Older Prefrontal Cortex of Healthy Adults

“…Cytochrome c oxidase (CCO) is a mitochondrial enzyme that consumes oxygen to produce adenosine triphosphate (ATP). The continuous and active synthesis of ATP by CCO provides intracellular energy to neurons and is essential for the normal operation of the human brain [10,11]. Thus, a close correlation or coherence must exist between local mitochondrial (or metabolic) and neurovascular (or hemodynamic) coupling, which is termed metabolic-hemodynamic coupling hereafter.…”

“…The four new neurophysiological metrics can be derived from noninvasive measurements of 2channel broadband near-infrared spectroscopy (bbNIRS) obtained from the forehead of human participants [8,10,19]. This portable device employs near-infrared light to non-invasively detect changes in chromophore concentrations, encompassing oxidized cytochrome c oxidase ([CCO]) and oxygenated hemoglobin ([HbO]) [29,30].…”

“…As shown in Figure 5(b) and Refs. [8,10], the bbNIRS system employed in this study was designed with two channels to collect data concurrently from each lateral forehead of the participant. The two light sources used were halogen lamps (OSL2IR, Thorlabs, Inc., NJ, USA) emitting broadband white light.…”