使用经颅磁刺激(TMS)的研究表明,当靶向初级运动皮层(M1)时,施加电流的方向和强度的重要性。通过改变这些,有可能刺激不同的神经元素子集,如运动诱发电位(MEP)和运动行为的调制所示。后者也涉及运动前区域,其中,补充前运动区域(pre-SMA)最近在运动抑制研究中受到了广泛关注。有可能,与M1类似,不同的神经元群体可以通过改变TMS的方向和强度来激活;然而,没有直接的电生理结果限制了这项研究.可以通过结合TMS和脑电图(TMS-EEG)量化直接皮层反应来解决该问题。我们研究了可变线圈取向的影响(0°,90°,180°和270°)和刺激强度(100%,120%和140%的静息运动阈值)对局部平均场电位(LMFP),经颅诱发电位(TEP)峰值和来自SMA前刺激的TMS相关频谱扰动(TRSP)。因此,早期和晚期LMFP和峰值较大,线圈手柄指向后方(0°)和横向(90°)。对于β-γ范围内的TRSP也是如此,但是,令人惊讶的是,θ-αTRSP在线圈指向180°时较大。90°的方向激活了右侧M1,如MEPs激发所示,从而限制了刺激的空间特异性。这些结果表明,当刺激预SMA时,线圈取向和刺激强度是关键的。
Studies using transcranial magnetic stimulation (TMS) have demonstrated the importance of direction and intensity of the applied current when the primary motor cortex (M1) is targeted. By varying these, it is possible to stimulate different subsets of neural elements, as demonstrated by modulation of motor evoked potentials (MEPs) and motor behaviour. The latter involves premotor areas as well, and among them, the presupplementary motor area (pre-SMA) has recently received significant attention in the study of motor inhibition. It is possible that, similar to M1, different neuronal populations can be activated by varying the direction and intensity of TMS; however, the absence of a direct electrophysiological outcome has limited this investigation. The problem can be solved by quantifying direct cortical responses by means of combined TMS and electroencephalography (TMS-EEG). We investigated the effect of variable coil orientations (0°, 90°, 180° and 270°) and stimulation intensities (100%, 120% and 140% of resting motor threshold) on local mean field potential (LMFP), transcranial evoked potential (TEP) peaks and TMS-related spectral perturbation (TRSP) from pre-SMA stimulation. As a result, early and late LMFP and peaks were larger, with the coil handle pointing posteriorly (0°) and laterally (90°). This was true also for TRSP in the β-γ range, but, surprisingly, θ-α TRSP was larger with the coil pointing at 180°. A 90° orientation activated the right M1, as shown by MEPs elicitation, thus limiting the spatial specificity of the stimulation. These results suggest that coil orientation and stimulation intensity are critical when stimulating the pre-SMA.