Jarczok Tomasz A, Roebruck Friederike, Pokorny Lena, Biermann Lea, Roessner Veit, Klein Christoph, Bender Stephan
Department of Child and Adolescent Psychiatry, Psychosomatics, and Psychotherapy, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany.
Department of Child and Adolescent Psychiatry, Faculty of Medicine, TU Dresden, Dresden, Germany.
Front Neurosci. 2021 Mar 12;15:616667. doi: 10.3389/fnins.2021.616667. eCollection 2021.
Transcranial magnetic stimulation (TMS)-evoked potentials (TEPs) allow for probing cortical functions in health and pathology. However, there is uncertainty whether long-latency TMS-evoked potentials reflect functioning of the targeted cortical area. It has been suggested that components such as the TMS-evoked N100 are stereotypical and related to nonspecific sensory processes rather than transcranial effects of the changing magnetic field. In contrast, TEPs that vary according to the targeted brain region and are systematically lateralized toward the stimulated hemisphere can be considered to reflect activity in the stimulated brain region resulting from transcranial electromagnetic induction.
TMS with concurrent 64-channel electroencephalography (EEG) was sequentially performed in homologous areas of both hemispheres. One sample of healthy adults received TMS to the dorsolateral prefrontal cortex; another sample received TMS to the temporo-occipital cortex. We analyzed late negative TEP deflections corresponding to the N100 component in motor cortex stimulation.
TEP topography varied according to the stimulation target site. Long-latency negative TEP deflections were systematically lateralized (higher in ipsilateral compared to contralateral electrodes) in electrodes over the stimulated brain region. A calculation that removes evoked components that are not systematically lateralized relative to the stimulated hemisphere revealed negative maxima located around the respective target sites.
TEPs contain long-latency negative components that are lateralized toward the stimulated hemisphere and have their topographic maxima at the respective stimulation sites. They can be differentiated from co-occurring components that are invariable across different stimulation sites (probably reflecting coactivation of peripheral sensory afferences) according to their spatiotemporal patterns. Lateralized long-latency TEP components located at the stimulation site likely reflect activity evoked in the targeted cortex region by direct transcranial effects and are therefore suitable for assessing cortical functions.
经颅磁刺激（TMS）诱发电位（TEP）可用于探究健康和病理状态下的皮质功能。然而，长潜伏期TMS诱发电位是否反映目标皮质区域的功能仍存在不确定性。有人认为，诸如TMS诱发的N100等成分具有刻板性，与非特异性感觉过程有关，而非变化磁场的经颅效应。相比之下，根据目标脑区而变化且系统地偏向受刺激半球的TEP可被认为反映了经颅电磁感应在受刺激脑区产生的活动。
在两个半球的同源区域依次进行TMS并同步记录64导脑电图（EEG）。一组健康成年人接受对背外侧前额叶皮质的TMS；另一组接受对颞枕叶皮质的TMS。我们分析了运动皮质刺激中与N100成分相对应的晚期负向TEP偏转。
TEP地形图根据刺激靶点部位而变化。在受刺激脑区上方的电极中，长潜伏期负向TEP偏转系统地偏向一侧（同侧电极比 contralateral电极更高）。一种去除相对于受刺激半球未系统地偏向一侧的诱发成分的计算方法显示，负向最大值位于各自的靶点部位周围。
TEP包含向受刺激半球偏向一侧的长潜伏期负向成分，其地形图最大值位于各自的刺激部位。根据其时空模式，它们可与在不同刺激部位不变的同时出现的成分（可能反映外周感觉传入的共同激活）区分开来。位于刺激部位的偏向一侧的长潜伏期TEP成分可能反映了经颅直接效应在目标皮质区域诱发的活动，因此适合用于评估皮质功能。
