Department of Neurosurgery, School of Medicine, Oita University, Oita, Japan.
Faculty of Medicine, Hospital Informatic Center, Oita University, Oita, Japan.
PLoS One. 2022 Aug 15;17(8):e0272268. doi: 10.1371/journal.pone.0272268. eCollection 2022.
Continuous theta-burst stimulation (cTBS) is a noninvasive repetitive brain stimulation protocol that suppresses the excitability of the primary motor cortex. It induces cerebral cortical inhibition by increasing inhibitory interneuronal excitability that is associated with increases in gamma-aminobutyric acid (GABA) concentration in the stimulated cortices. cTBS has been applied in the rehabilitation of stroke patients to modulate interhemispheric imbalance. However, the precise mechanisms of cTBS in remote brain areas remain uncertain. We evaluated cTBS-induced GABA level changes in bilateral sensorimotor cortices using GABA-edited magnetic resonance spectroscopy, alternations of motor evoked potentials (MEPs), and resting-state networks (RSNs) using resting-state functional magnetic resonance imaging in 24 healthy right-handed adults (mean age: 34.4 ± 5.0 years). GABA levels in the stimulated left hemisphere significantly increased from baseline (p = 0.013), which was comparable with those of previous reports. GABA levels in the unstimulated right hemisphere showed a trend decrease. cTBS induced a significant decrease in right hand-MEP amplitudes (22.06% ± 43.50%) from baseline (p = 0.026) in accordance with GABA concentrations. However, multiple RSNs, including the default mode and primary motor networks, did not show any obvious differences between pre- and post-stimulus comparisons in the sensorimotor network using the dual regression approach. These results suggest that cTBS simultaneously increases ipsilateral GABA in the stimulated left hemisphere and decreases contralateral GABA in the unstimulated right hemisphere. Neuromodulation following cTBS may be associated with the interhemispheric inhibition because of alterations in GABA levels between the stimulated and unstimulated cortices.
经颅磁刺激（TMS）是一种非侵入性的重复大脑刺激方案，可抑制初级运动皮层的兴奋性。它通过增加抑制性中间神经元的兴奋性来诱导皮质抑制，从而与刺激皮质中γ-氨基丁酸（GABA）浓度的增加相关联。TMS 已应用于脑卒中患者的康复治疗中，以调节大脑半球间的不平衡。然而，TMS 在远程脑区的确切机制仍不确定。我们使用 GABA 编辑磁共振波谱（MRS）评估了 24 名健康右利手成年人（平均年龄：34.4±5.0 岁）双侧感觉运动皮层 TBS 诱导的 GABA 水平变化，使用静息状态功能磁共振成像（fMRI）评估运动诱发电位（MEP）和静息态网络（RSN）的交替。刺激左侧半球的 GABA 水平从基线显著增加（p=0.013），与以往报道一致。未刺激的右侧半球的 GABA 水平呈下降趋势。TBS 诱导右手上肢 MEP 振幅显著降低（22.06%±43.50%）（p=0.026），与 GABA 浓度一致。然而，使用双回归方法，在感觉运动网络中，多个 RSN，包括默认模式和初级运动网络，在刺激前后比较中没有显示出任何明显差异。这些结果表明，TBS 同时增加了刺激左侧半球的同侧 GABA，并降低了未刺激右侧半球的对侧 GABA。TBS 后的神经调节可能与 GABA 水平在刺激和未刺激皮质之间的变化有关，与大脑半球间抑制有关。
