Institute of Psychological Sciences, Hangzhou Normal University, Hangzhou, China.
Zhejiang Key Laboratory for Research in Assessment of Cognitive Impairments, Hangzhou, China.
Brain Behav. 2020 Jul;10(7):e01670. doi: 10.1002/brb3.1670. Epub 2020 Jun 7.
Repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex (M1) can modulate brain activity both in the stimulated site and remote brain areas of the sensorimotor network. However, the modulatory effects of rTMS at different frequencies remain unclear. Here, we employed finger-tapping task-based fMRI to investigate alterations in activation of the sensorimotor network after the application of rTMS over the left M1 at different frequencies.
Forty-five right-handed healthy participants were randomly divided into three groups by rTMS frequency (HF, high-frequency, 3 Hz; LF, low-frequency, 1 Hz; and SHAM) and underwent two task-fMRI sessions (RH, finger-tapping with right index finger; LH, finger-tapping with left index finger) before and after applying rTMS over the left M1. We defined regions of interest (ROIs) in the sensorimotor network based on group-level activation maps (pre-rTMS) from RH and LH tasks and calculated the percentage signal change (PSC) for each ROI. We then assessed the differences of PSC within HF or LF groups and between groups.
Application of rTMS at different frequencies resulted in a change in activation of several areas of the sensorimotor network. We observed the increased PSC in M1 after high-frequency stimulation, while we detected the reduced PSC in the primary sensory cortex (S1), ventral premotor cortex (PMv), supplementary motor cortex (SMA), and putamen after low-frequency stimulation. Moreover, the PSC in the SMA, dorsal premotor cortex (PMd), and putamen in the HF group was higher than in the LF group after stimulation.
Our findings suggested that activation alterations within sensorimotor network are dependent on the frequency of rTMS. Therefore, our findings contribute to understanding the effects of rTMS on brain activation in healthy individuals and ultimately may further help to suggest mechanisms of how rTMS could be employed as a therapeutic tool.
经颅重复磁刺激（rTMS）作用于初级运动皮层（M1）可调节刺激部位及体感运动网络的远隔脑区的脑活动。然而，不同频率 rTMS 的调制效应尚不清楚。本研究采用基于手指敲击任务的 fMRI 技术，研究了左 M1 不同频率 rTMS 刺激后体感运动网络激活的变化。
45 名右利手健康参与者按 rTMS 频率（HF，高频，3Hz；LF，低频，1Hz；SHAM）随机分为三组，在左 M1 施加 rTMS 前后进行两次基于手指敲击任务的 fMRI 扫描（RH，用右食指敲击；LH，用左食指敲击）。我们基于 RH 和 LH 任务的组水平激活图（预 rTMS）定义了体感运动网络中的感兴趣区（ROI），并计算了每个 ROI 的信号变化百分比（PSC）。然后我们评估了 HF 或 LF 组内和组间的 PSC 差异。
不同频率的 rTMS 刺激导致体感运动网络中几个区域的激活发生变化。我们观察到高频刺激后 M1 的 PSC 增加，而低频刺激后初级感觉皮层（S1）、腹侧运动前皮层（PMv）、辅助运动皮层（SMA）和壳核的 PSC 减少。此外，刺激后 HF 组 SMA、背侧运动前皮层（PMd）和壳核的 PSC 高于 LF 组。
我们的研究结果表明，体感运动网络内的激活变化依赖于 rTMS 的频率。因此，我们的研究结果有助于理解 rTMS 对健康个体大脑激活的影响，最终可能有助于进一步提出 rTMS 如何作为一种治疗工具的机制。
