The effect of photobiomodulation on activity of the human brain

Abstract

The global aim of this thesis was to explore the effect of photobiomodulation (PBM) on the human brain, with the findings leading hopefully to further establish this treatment as a viable therapeutic option for patients, particularly those with neurodegenerative disease. The results are presented as peer reviewed publications, each with their own chapters (2-5). Chapter 1 contains the literature review, while chapter 6 contains a general discussion.

This thesis included functional magnetic resonance imaging (fMRI) research on the effect of PBM on healthy young brains (chapter 2 and 3), along with clinical case studies of patients with neurodegenerative disease (chapter 4) and a thorough systematic review of the effect of PBM on neurodegeneration-induced neuroinflammation (chapter 5). Together, all these components of the thesis offer a robust and diverse exploration of the effect of PBM on healthy and diseased brains.

In chapter 2, with the use of fMRI, the effect of PBM on human brain activity in young healthy individuals indicated a reduction in default mode network connectivity during the execution of a task (ie, finger tapping). It was suggested that PBM helped focus attention on the sensorimotor task being undertaken by the individuals. In chapter 3, again with the use of fMRI, the effect of PBM indicated no change in resting state brain connectivity in the brains of healthy individuals. From the results in chapter 2 and 3, it was concluded that in a healthy brain state, PBM had a measurable effect such as altering brain connectivity when the brain is in an evoked task state, for example when undergoing a sensorimotor task, but not during passive rest. In Chapter 4, the effect of PBM on the clinical motor signs and non-motor symptoms of elderly patients with neurodegenerative disease (ie Parkinson’s disease) was observed and recorded. Almost all the signs and symptoms of the patients showed improvement and none got worse. For example, improvement in motor signs