Transcranial Photobiomodulation

Delayed neurocognitive recovery is a common neurocognitive complication in older patients after surgery, especially those with preoperative neurocognitive decline. Transcranial photobiomodulation therapy is a novel neuromodulation technique using transcranial low-power light to modulate brain biological functions. This technique has been used to treat various neurological or psychiatric conditions, including ischemic stroke, traumatic brain injury, and major depression. This study is designed to explore whether using transcranial photobiomodulation therapy during the perioperative period can reduce the incidence of delayed neurocognitive recovery in older patients with pre-existing neurocognitive impairment.

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.

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.