Neuromodulatory effects of offline low-frequency repetitive transcranial magnetic stimulation of the motor cortex: A functional magnetic resonance imaging study.

Yu-Sun Min,Hui Joong Lee,Yongmin Chang,Kyung Eun Jang,Yang-Soo Lee,Seong Uk Jin,Jongmin Lee,Byung-Joo Lee,Tae-Du Jung,Jang Woo Park

doi:10.1038/srep36058

Abstract

Repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex (M1) can modulate cortical excitability and is thought to influence activity in other brain areas. In this study, we investigated the anatomical and functional effects of rTMS of M1 and the time course of after-effects from a 1-Hz subthreshold rTMS to M1. Using an “offline” functional magnetic resonance imaging (fMRI)-rTMS paradigm, neural activation was mapped during simple finger movements after 1-Hz rTMS over the left M1 in a within-subjects repeated measurement design, including rTMS and sham stimulation. A significant decrease in the blood oxygen level dependent (BOLD) signal due to right hand motor activity during a simple finger-tapping task was observed in areas remote to the stimulated motor cortex after rTMS stimulation. This decrease in BOLD signal suggests that low frequency subthreshold rTMS may be sufficiently strong to elicit inhibitory modulation of remote brain regions. In addition, the time course patterns of BOLD activity showed this inhibitory modulation was maximal approximately 20 minutes after rTMS stimulation.

Highlights

On stimulation frequency, intensity, duration, and experimental design[11,12,13], it remains uncertain how Repetitive transcranial magnetic stimulation (rTMS) after-effects affect neural activity across different brain regions over time
We used an “offline” functional magnetic resonance imaging-rTMS paradigm to investigate two questions: (1) whether the effect of rTMS on M1 is limited to brain structures within or beyond the motor network, and (2) whether the time course of the neural activity associated with motor task shows a different activation pattern before and after a low frequency rTMS over M1
We focused on two issues: (1) whether the effect of inhibitory rTMS on M1 is limited to brain structures within the motor network and (2) whether there is a change in the time course pattern of inhibitory rTMS after-effects during an active finger-tapping task

Summary

Introduction

On stimulation frequency, intensity, duration, and experimental design[11,12,13], it remains uncertain how rTMS after-effects affect neural activity across different brain regions over time. We used an “offline” functional magnetic resonance imaging (fMRI)-rTMS paradigm to investigate two questions: (1) whether the effect of rTMS on M1 is limited to brain structures within or beyond the motor network, and (2) whether the time course of the neural activity associated with motor task shows a different activation pattern before and after a low frequency rTMS over M1. We investigated the time course of after-effects from rTMS of M1 using a serial consecutive fMRI. For targeting of the M1 across subjects and stimulation sessions, we employed an MRI-guided rTMS method

Methods

Results

Conclusion