Modulating cerebrospinal fluid dynamics using pulsed photobiomodulation: the dose and skin-colour dependence

Motivation: The use of photobiomodulation (PBM) to enhance glymphatic drainage and thus neurotoxic waste clearance, makes it a promising therapeutic tool against neurodegenerative diseases like Alzheimer's. Goal(s): This study investigates whether PBM can modulate cerebrospinal fluid (CSF) flow in healthy young adults. Approach: Adjusting key parameters like wavelength, frequency, and power will determine the most effective PBM protocol. Results: Our data demonstrates 4 min of PBM-induced increases in CSF flow, greater for higher power density, lower wavelength and pulsation frequency. Intranasal PBM achieved similar performance as transcranial PBM, albeit with 1/20 the power. Participant melanin levels also impact PBM's effect on CSF flow. Impact: Photobiomodulation (PBM) has shown to enhance glymphatic drainage by modulating CSF flow, but in a delivery and dose-dependent manner. The significant wavelength-frequency interactions and melanin effects demonstrate the need to optimize PBM delivery in different settings.