This study investigates the frequency-dependent neuromodulatory effects of transcranial photobiomodulation (tPBM) over the primary motor cortex (M1) on cortical excitability and fine motor performance in healthy young adults. Using a randomized, double-blind, sham-controlled, 5-arm crossover design, 20 healthy participants will undergo five experimental conditions separated by a mandatory 7-day washout period: Continuous Wave (CW), 10 Hz pulsed tPBM, 40 Hz pulsed tPBM, 100 Hz pulsed tPBM, and a Sham control. To isolate pulse frequency while holding peak intensity constant, all active interventions will utilize an identical peak irradiance, with pulsed modes operating at a 50% duty cycle (delivering 50% of the cumulative energy dose relative to CW). Primary outcomes include corticospinal excitability measured via single- and paired-pulse Transcranial Magnetic Stimulation (TMS), alongside fine motor speed and dexterity assessed via a computerized finger-tapping task.
Voluntary Participation: Participants who are clear of their cognitive faculties, capable of understanding all experimental procedures, and who provide written informed consent prior to enrollment.
Neurologically and Psychiatrically Healthy Status: Individuals with no current or prior history of neurological, neurodevelopmental, or psychiatric conditions;
Age Range: Young adult volunteers aged between 18 and 35 years.
Use of any continuous psychotropic medication within the past 12 months.
Any current psychiatric diagnosis based on the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5).
Diagnosis of any neurological disorder capable of altering cortical excitability (e.g., seizures/epilepsy, cerebrovascular accidents/stroke, brain tumors).
Any clinical, psychological, or social condition that, in the investigator's opinion, places the participant at an increased risk, compromises participant safety, or precludes full compliance and successful completion of the study protocol.
Hospital de Clinicas de Porto Alegre
Lead sponsor
Federal University of Rio Grande do Sul
Collaborator
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior.
Collaborator