Department of Psychology and Neurosciences, Leibniz Research Centre for Working Environment and Human Factors, Dortmund, Germany; Institute of Biomedical Engineering and Informatics, Technische Universität Ilmenau, Ilmenau, Germany.
Department of Psychology and Neurosciences, Leibniz Research Centre for Working Environment and Human Factors, Dortmund, Germany; Institute of Psychology, Federal Armed Forces University Munich, Neubiberg, Germany.
Brain Stimul. 2023 Mar-Apr;16(2):515-539. doi: 10.1016/j.brs.2023.02.010. Epub 2023 Feb 23.
Neurophysiological effects of transcranial direct current stimulation (tDCS) have been extensively studied over the primary motor cortex (M1). Much less is however known about its effects over non-motor areas, such as the prefrontal cortex (PFC), which is the neuronal foundation for many high-level cognitive functions and involved in neuropsychiatric disorders. In this study, we, therefore, explored the transferability of cathodal tDCS effects over M1 to the PFC. Eighteen healthy human participants (11 males and 8 females) were involved in eight randomized sessions per participant, in which four cathodal tDCS dosages, low, medium, and high, as well as sham stimulation, were applied over the left M1 and left PFC. After-effects of tDCS were evaluated via transcranial magnetic stimulation (TMS)-electroencephalography (EEG), and TMS-elicited motor evoked potentials (MEP), for the outcome parameters TMS-evoked potentials (TEP), TMS-evoked oscillations, and MEP amplitude alterations. TEPs were studied both at the regional and global scalp levels. The results indicate a regional dosage-dependent nonlinear neurophysiological effect of M1 tDCS, which is not one-to-one transferable to PFC tDCS. Low and high dosages of M1 tDCS reduced early positive TEP peaks (P30, P60), and MEP amplitudes, while an enhancement was observed for medium dosage M1 tDCS (P30). In contrast, prefrontal low, medium and high dosage tDCS uniformly reduced the early positive TEP peak amplitudes. Furthermore, for both cortical areas, regional tDCS-induced modulatory effects were not observed for late TEP peaks, nor TMS-evoked oscillations. However, at the global scalp level, widespread effects of tDCS were observed for both, TMS-evoked potentials and oscillations. This study provides the first direct physiological comparison of tDCS effects applied over different brain areas and therefore delivers crucial information for future tDCS applications.
经颅直流电刺激（tDCS）对初级运动皮层（M1）的神经生理效应已得到广泛研究。然而，关于其对非运动区域（如前额叶皮层[PFC]）的影响却知之甚少，PFC 是许多高级认知功能的神经元基础，并与神经精神疾病有关。因此，在这项研究中，我们探索了将 M1 上的阴极 tDCS 效应转移到 PFC 的可能性。18 名健康的人类参与者（11 名男性和 8 名女性）每人参与了 8 次随机分组的实验，在这些实验中，将四种阴极 tDCS 剂量（低、中、高和假刺激）施加到左侧 M1 和左侧 PFC 上。通过经颅磁刺激（TMS）-脑电图（EEG）和 TMS 诱发的运动诱发电位（MEP）评估 tDCS 的后效，以 TMS 诱发的电位（TEP）、TMS 诱发的振荡和 MEP 振幅变化作为结果参数。在区域和全局头皮水平上研究了 TEPs。结果表明，M1 tDCS 的区域剂量依赖性非线性神经生理效应不是一对一地可转移到 PFC tDCS。M1 tDCS 的低和高剂量降低了早期正 TEP 峰值（P30、P60）和 MEP 振幅，而中剂量 M1 tDCS 则观察到增强（P30）。相比之下，前额叶皮层的低、中、高剂量 tDCS 均降低了早期正 TEP 峰值振幅。此外，对于两个皮质区域，区域 tDCS 诱导的调制效应在晚期 TEP 峰值和 TMS 诱发的振荡中均未观察到。然而，在全局头皮水平上，两种 TMS 诱发的电位和振荡都观察到了 tDCS 的广泛影响。本研究首次对不同脑区应用 tDCS 效应进行了直接的生理比较，因此为未来的 tDCS 应用提供了重要信息。
