Frequency-Dependent Effects of Transcranial Photobiomodulation on Cortical Excitability

This study aims to investigate the frequency-dependent effects of near-infrared (NIR) transcranial photobiomodulation (tPBM) on human cortical excitability and fine motor performance. A cohort of 20 healthy adult volunteers (aged 18-35 years) will participate in a randomized, double-blind, sham-controlled, single-center study utilizing a within-subject, five-arm crossover design. Each participant will undergo five distinct experimental conditions separated by a strict washout period: active Continuous Wave (CW) tPBM, active pulsed tPBM at three neural oscillation frequencies (10 Hz, 40 Hz, and 100 Hz), and an inactive Sham comparator. All interventions will be delivered using a clinical-grade near-infrared device. To isolate the specific effects of pulse frequency from overall energy delivery, the total energy dose (cumulative Joules) and total exposure time will be held perfectly constant across all active arms. The pulsed conditions will keeps the average irradiance and cumulative fluence identical to the continuous wave mode. Cortical excitability will be assessed via single- and paired-pulse Transcranial Magnetic Stimulation (TMS) protocols over the primary motor cortex (M1). Fine motor performance will be quantified using a smartphone-based Finger Tapping Test (FTT). Safety and systemic parameters will be tracked using the Systematic Assessment for Treatment Emergent Events - Systematic Inquiry (SAFTEE-SI) and vital signs. The central hypothesis is that distinct modulation frequencies will differentially influence corticospinal excitability and motor execution, independent of the total energy delivered.

NCT Number	NCT07707284
Lead Sponsor	Hospital de Clinicas de Porto Alegre Collaborators: Federal University of Rio Grande do Sul, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior.
Conditions	Healthy Volunteers (HV), Transcranial Photobiomodulation, Cortical Excitability
Enrollment	20 participants
Start Date	2027-05
Primary Completion	2028-05 (estimated)
Study Completion	2028-07 (estimated)
Updated on ClinicalTrials.gov	2026-07-28