A Single Session of rTMS Enhances Small-Worldness in Writer's Cramp: Evidence from Simultaneous EEG-fMRI Multi-Modal...

Area of Science:

• Neuroscience
• Brain Connectivity
• Graph Theory

Background:

• Repetitive transcranial magnetic stimulation (rTMS) is known to induce widespread brain connectivity changes.
• The specific network topology alterations following a single rTMS session remain less understood.

Purpose of the Study:

• To investigate if a single rTMS session induces small-world network morphology.
• To analyze network alterations using multi-modal graph theory analysis of simultaneous EEG-fMRI.

Main Methods:

• Simultaneous EEG-fMRI was acquired from 14 writer's cramp patients before and after a single rTMS session.
• Graph theory measures, including clustering coefficient, path length, and small-world index, were calculated for EEG and resting-state fMRI (rsfMRI).
• Multi-modal graph theory analysis correlated EEG and fMRI clustering coefficients.

Main Results:

• A single rTMS session significantly increased clustering coefficient and small-worldness in both EEG and fMRI (p < 0.05).
• Multi-modal analysis showed significant modulations in fronto-parietal regions immediately post-rTMS.
• rsfMRI revealed additional modulations in deep brain regions like the cerebellum, insula, and medial frontal lobe.

Conclusions:

• Multi-modal graph theory analysis of simultaneous EEG-fMRI aids in understanding rTMS neurobiology in vivo.
• Coinciding EEG and rsfMRI evidence supports small-world morphology in the acute phase of network hyper-connectivity.
• Acute changes from low-frequency rTMS are likely not random noise but represent genuine network alterations.