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. 2025 Mar 13:19:1514087.
doi: 10.3389/fnhum.2025.1514087. eCollection 2025.

Pilot study comparing effects of infrared neuromodulation and transcranial magnetic stimulation using magnetic resonance imaging

Sophia A Bibb  1   2 , Emily J Yu  3 , M Fiona Molloy  1   4 , John LaRocco  2 , Patricia Resnick  5 , Kevin Reeves  2 , K Luan Phan  2 , Sanjay Krishna  6 , Zeynep M Saygin  1
Affiliations

Pilot study comparing effects of infrared neuromodulation and transcranial magnetic stimulation using magnetic resonance imaging

Sophia A Bibb et al. Front Hum Neurosci. .

Abstract

No prior work has directly compared the impacts of transcranial photobiomodulation (tPBM) and transcranial magnetic stimulation (TMS) on the human brain. This within-subjects pilot study compares the effects of tPBM and TMS of human somatomotor cortex on brain structural and functional connectivity. Eight healthy participants underwent four lab visits each, each visit consisting of a pre-stimulation MRI, stimulation or sham, and a post-stimulation MRI, respectively. Stimulation and sham sessions were counterbalanced across subjects. Collected measures included structural MRI data, functional MRI data from a finger-tapping task, resting state functional connectivity, and structural connectivity. Analyses indicated increased activation of the left somatomotor region during a right-hand finger-tapping task following both tPBM and TMS. Additionally, trending increases in left-lateralized functional and structural connectivity from M1 to thalamus were observed after tPBM, but not TMS. Thus, tPBM may be superior to TMS at inducing changes in connected nodes in the somatomotor cortex, although further research is warranted to explore the potential therapeutic benefits and clinical utility of tPBM.

Keywords: fractional anisotropy; functional magnetic resonance imaging; photobiomodulation; resting-state connectivity; transcranial magnetic stimulation.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Transcranial photobiomodulation (tPBM) system and setup. (Left) Laser system control console. (Right) Participant with headset, with laser situated over the vertex of the head (Cz).
FIGURE 2
FIGURE 2
Effects of stimulation on fMRI activation. (A) Probabilistic map across subjects of changes in somatomotor activation after stimulation, thresholded to show effects in over 4/8 subjects. Black outline indicates somatomotor region of interest (ROI). (B) Individual subject changes in activation (percent signal change; PSC) of subject-specific somatomotor ROIs after stimulation, normalized by sham changes. Individual-subject data points indicated via open circles, with standard error in black lines.
FIGURE 3
FIGURE 3
Effects of stimulation on structural and functional connectivity. (A) Changes in white matter FA after transcranial photobiomodulation (tPBM) stimulation, normalized by changes during sham session; cluster corrected group map at p < 0.07. (B) Changes in probabilistic tractography performed per subject to map motor to thalamic white matter connections [illustrated on representative subject in inset, with arrows indicating motor and thalamic region of interest (ROIs)]. Bar plots show changes after tPBM and transcranial magnetic stimulation (TMS) on left hemisphere (LH) motor-thalamic structural connectivity. (C) Changes in stimulation on LH motor-thalamic functional connectivity. Individual-subject data points indicated via open circles, with standard error in black lines.
See this image and copyright information in PMC

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