Date of Award

Spring 2025

Document Type

Thesis

Publisher

Santa Clara : Santa Clara University, 2025

Degree Name

Master of Science (MS)

Department

Bioengineering

First Advisor

Julia Scott

Abstract

BACKGROUND: Transcranial photobiomodulation (tPBM) is an experimental treatment that potentially slows the progression of neurodegenerative diseases by affecting cerebral blood flow, inflammatory processes, and ATP production. Preliminary tPBM studies in humans show that tPBM stimulation can positively influence cognitive function. The objective of this study was to build a cohesive hardware and software system safe for human use, and use that system and another tPBM device to test the cognitive effects and EEG and HRV biomarkers of tPBM.

METHODS: A lab-built prototype device was designed based on the industry standard Neuronic LIGHT tPBM device. The prototype consists of 360 LEDs at 10 focused locations over the head. Both tPBM devices used 1070 nm LEDs and investigated candidate cognitive effects and biomarkers by testing the cognitive performance of healthy adults (N=22) before and after tPBM at 6 Hz with a 90% duty cycle compared to a sham procedure. Mechanisms associated with tPBM were measured by PPG and EEG. Heart rate variability (HRV) derived from PPG served as a biomarker for cerebrovascular effects. Theta power was used as a biomarker for change in neural activity associated with tPBM. Linear mixed effects models were used to evaluate the independent effect of tPBM on cognitive performance, theta power, and HRV.

RESULTS: The prototype device built had all the same basic functionalities of the Neuronic LIGHT device and had measured irradiance and fluence values of 105 mW/cm² and 56.7 J/cm², respectively. Initial results indicate within subject changes in working memory and processing speed were not associated with Neuronic or prototype protocols. Additionally, HRV and EEG PSD values were not associated with the tPBM protocols for either device.

DISCUSSION: Additional testing needs to be conducted at different stimulation parameters with larger sample sizes to determine the reliable effects of tPBM on cognition and physiological features. In the future, the relationship between features like EEG, HRV, and cognition should be investigated to determine if there is a direct relationship between physiological features and cognitive function.

Download

Share

COinS