High-Frequency rTMS of the Motor Cortex Modulates Cerebellar and Widespread Activity as Revealed by SVM.

Jue Wang,Yu-Feng Zang,Yun-Ying Wu,Hong-Xiao Wang,Ying Jing,Xiao-Long Li,Na Zhao,Zi-Jian Feng,Jian Zhang,Xin-Ping Deng

doi:10.3389/fnins.2020.00186

Abstract

Functional magnetic resonance imaging (fMRI) studies have shown that the effect of repetitive transcranial magnetic stimulation (rTMS) can induce changes in remote brain regions. In the stimulated regions, low-frequency (≤1 Hz) rTMS induces inhibitory effects, while high-frequency (≥5 Hz) stimulation induces excitatory effects. However, these stereotypical effects arising from low- and high-frequency stimulation are based on measurements of motor evoked potentials (MEPs) induced by pulsed stimulation. To test the effects of rTMS on remote brain regions, the current study recruited 31 young healthy adults who participated in three rTMS sessions (10 Hz high frequency, 1 Hz low frequency, and sham) on three separate days. The stimulation target was based on individual fMRI activation in the motor cortex evoked by a finger movement task. Pre- and post-rTMS resting-state fMRI (RS-fMRI) were acquired. Regional homogeneity (ReHo) and degree centrality (DC) were calculated to measure the local and global connectivity, respectively. Compared with the sham session, high-frequency (10 Hz) rTMS significantly increased ReHo and DC in the right cerebellum, while low-frequency (1 Hz) stimulation did not significantly alter ReHo or DC. Then, using a newly developed PAIR support vector machine (SVM) method, we achieved accuracy of 93.18–97.24% by split-half validation for pairwise comparisons between conditions for ReHo or DC. While the univariate analyses suggest that high-frequency rTMS of the left motor cortex could affect distant brain activity in the right cerebellum, the multivariate SVM results suggest that both high- and low-frequency rTMS significantly modulated widespread brain activity. The current findings are useful for increasing the understanding of the mechanisms of rTMS, as well as guiding precise individualized rTMS treatment of movement disorders.

Highlights

Repetitive transcranial magnetic stimulation is a safe and non-invasive technique for the treatment of brain diseases
ANOVAs showed significant effects between the three conditions (Low, High, and Sham) in the right cerebellum VIII extending to VIIb for both Regional homogeneity (ReHo) and degree centrality (DC) (Figure 2 and Table 2)
We found significant condition effects of repetitive transcranial magnetic stimulation (rTMS) on local connectivity (ReHo) and global connectivity (DC) in areas VIII/VIIb of the right cerebellum in healthy participants

Summary

Introduction

Repetitive transcranial magnetic stimulation (rTMS) is a safe and non-invasive technique for the treatment of brain diseases. Resting-state functional magnetic resonance imaging (RSfMRI) is increasingly being used to detect TMS-induced brain activity at the network level Many studies using this technique have found that rTMS modulates brain networks or functional connectivity (FC) (Eldaief et al, 2011; Chen et al, 2013; Halko et al, 2014; Nettekoven et al, 2014, 2015; Wang et al, 2014; Watanabe et al, 2014; Andoh et al, 2015; Cocchi et al, 2015, 2016; Ji et al, 2017). While RS-fMRI studies into FC have increased our understanding of the complex mechanisms of the modulatory effects of rTMS on brain activity, there are two limitations for analysis of FC or networks. This makes it difficult to compare the results between different studies using network or FC analysis

Methods

Results

Discussion

Conclusion