Illuminating Neural Pathways: Modulating Motor Cortex and Related Pathways with Photobiomodulation
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Date
2024-05
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The Ohio State University
Abstract
Parkinson’s Disease (PD) and Major Depressive Disorder (MDD) are prevalent disorders of the brain which may benefit from treatment via nonpharmacological neuromodulation. Current approaches include transcranial magnetic stimulation (TMS) which has been shown to noninvasively stimulate the brain with transient effects. However, the effects of TMS are limited to superficial regions. A newer noninvasive method that can reach subcortical structures is transcranial photobiomodulation (tPBM), which uses visible to near-infrared light to stimulate neurons. In this work, we have built a multi-wavelength tPBM system to assess the effects of light of 1064 nm wavelength on brain activity and connectivity. Given that motor skills are affected by MDD and PD, we focused on stimulating the primary motor cortex (M1).
Healthy adult volunteers (N=10) underwent four sessions of stimulation consisting of active tPBM and TMS along with respective sham sessions. Structural and task fMRI were taken before and after stimulation. Participants performed a motor task to explore the effect of stimulation within each individual’s motor cortices.
Here we report that tPBM successfully stimulated M1 to a similar amount of activation as TMS in a safe and short-term manner. The effects of tPBM and TMS stimulation on motor activation was not significantly different within participants, suggesting that the two types of stimulation induce similar effects on the somatomotor cortex. We also observed significant changes in functional and structural connectivity between the motor cortex and thalamus after PBM stimulation. These results are in line with previous literature. Interestingly, TMS stimulation did not seem to affect structural and functional connectivity.
Our preliminary results reveal that tPBM can cause changes in activation and connectivity of the somatomotor cortex with short-term effects that are comparable to the gold standard of neuromodulation, TMS. tPBM is still a relatively novel technique with more to be explored. PBM harnesses the neuroprotective properties of brain cells and may be useful when pharmacological options are unsuccessful or cannot be tolerated. Compared to other stimulation methods, PBM can penetrate further into the brain, providing more options for treatments of mental illnesses.
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Keywords
Photobiomodulation, Cognitive Neuroscience, Lasers, Brain, Neuromodulation