Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, University College London, WC1N 3BG, London, United Kingdom.
Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, University College London, WC1N 3BG, London, United Kingdom; Neurology, Neurophysiology and Neurobiology Unit, Department of Medicine, Università Campus Bio-Medico di Roma, Rome, Italy.
Brain Stimul. 2021 Jan-Feb;14(1):4-18. doi: 10.1016/j.brs.2020.10.011. Epub 2020 Oct 28.
BACKGROUND: the use of combined transcranial magnetic stimulation (TMS) and electroencephalography (EEG) for the functional evaluation of the cerebral cortex in health and disease is becoming increasingly common. However, there is still some ambiguity regarding the extent to which brain responses to auditory and somatosensory stimulation contribute to the TMS-evoked potential (TEP). OBJECTIVE/HYPOTHESIS: to measure separately the contribution of auditory and somatosensory stimulation caused by TMS, and to assess their contribution to the TEP waveform, when stimulating the motor cortex (M1). METHODS: 19 healthy volunteers underwent 7 blocks of EEG recording. To assess the impact of auditory stimulation on the TEP waveform, we used a standard figure of eight coil, with or without masking with a continuous noise reproducing the specific time-varying frequencies of the TMS click, stimulating at 90% of resting motor threshold. To further characterise auditory responses due to the TMS click, we used either a standard or a sham figure of eight coil placed on a pasteboard cylinder that rested on the scalp, with or without masking. Lastly, we used electrical stimulation of the scalp to investigate the possible contribution of somatosensory activation. RESULTS: auditory stimulation induced a known pattern of responses in electrodes located around the vertex, which could be suppressed by appropriate noise masking. Electrical stimulation of the scalp alone only induced similar, non-specific scalp responses in the in the central electrodes. TMS, coupled with appropriate masking of sensory input, resulted in specific, lateralized responses at the stimulation site, lasting around 300 ms. CONCLUSIONS: if careful control of confounding sources is applied, TMS over M1 can generate genuine, lateralized EEG activity. By contrast, sensory evoked responses, if present, are represented by non-specific, late (100-200 ms) components, located at the vertex, possibly due to saliency of the stimuli. Notably, the latter can confound the TEP if masking procedures are not properly used.
背景：联合经颅磁刺激（TMS）和脑电图（EEG）用于评估健康和疾病状态下大脑皮层的功能正变得越来越普遍。然而，对于听觉和体感刺激对 TMS 诱发电位（TEP）的贡献程度仍存在一些模糊性。
目的/假设：当刺激运动皮层（M1）时，分别测量 TMS 引起的听觉和体感刺激的贡献，并评估它们对 TEP 波形的贡献。
方法：19 名健康志愿者接受了 7 轮 EEG 记录。为了评估听觉刺激对 TEP 波形的影响，我们使用了标准的 8 字形线圈，有或没有用连续噪声掩蔽，该噪声再现 TMS 点击的特定时变频率，刺激强度为静息运动阈值的 90%。为了进一步描述 TMS 点击引起的听觉反应，我们使用了标准或假的 8 字形线圈，放置在一个放在头皮上的糊纸盒上，有或没有掩蔽。最后，我们使用头皮电刺激来研究体感激活的可能贡献。
结果：听觉刺激在电极周围的顶点引起了已知的反应模式，这些反应可以通过适当的噪声掩蔽来抑制。单独刺激头皮只会在中央电极引起类似的非特异性头皮反应。TMS 与适当的感觉输入掩蔽相结合，会在刺激部位产生特定的、偏侧化的反应，持续约 300 毫秒。
结论：如果对混杂来源进行仔细控制，TMS 刺激 M1 可以产生真实的、偏侧化的 EEG 活动。相比之下，如果存在感觉诱发反应，则表现为非特异性的、晚期（100-200 毫秒）的成分，位于顶点，可能是由于刺激的显著性。值得注意的是，如果没有正确使用掩蔽程序，后者可能会混淆 TEP。
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