Transcranial Near-Infrared Light: Dose-Dependent Effects on EEG Oscillations but not Cerebral Blood Flow

ABSTRACT Objective Our objective was to assess whether transcranial photobiomodulation (tPBM) with near-infrared light (NIR) shows modulatory effects on cerebral electrical activity through electroencephalogram (EEG) and cerebral blood flow (CBF). Background tPBM has emerged as a novel intervention for several neuropsychiatric conditions due to its neuroprotective and neuroenhancement effects. Methods We conducted a single-blind, sham-controlled pilot study to test the effect of continuous (c-tPBM), pulse (p-tPBM) and sham (s-tPBM) transcranial photobiomodulation on EEG oscillations and CBT using diffuse correlation spectroscopy (DCS) in a sample of ten healthy subjects [6 F/ 4 M; mean age 28.6 ± 12.9 (SD) years]. c-tPBM NIR (830 nm; 54.8 mW/cm²; 65.8 J/cm²; 2.3 kJ) and p-tPBM (830 nm; 10Hz; 54.8 mW/cm²; 33%; 21.7 J/cm²; 0.8 kJ) were delivered concurrently to the frontal areas (F4, Fp2, Fp1, F3 - total surface 35.8 cm²) by four LED clusters (TPBM-1000 Litecure). EEG and DCS recordings were performed weekly before, during, and after each tPBM session (in sequence: c-tPBM, s-tPBM and p-tPBM). Results Only c-tPBM significantly boosted gamma (t = 3.02, df = 7, p < .02) and beta (t = 2.91, df = 7, p < .03) EEG spectral powers in eyes-open recordings and gamma power (t = 3.61, df = 6, p < .015) in eyes-closed recordings, with the largest effects in the posterior regions. There was no significant effect of NIR-tPBM on CBF compared to sham. Conclusions Our data suggest a dose-dependent effect of tPBM with NIR (c-tPBM) on cerebral gamma and beta neuronal activity. Altogether, our findings support the neuromodulatory effect of transcranial NIR.