Department 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 Psychology and Neurosciences, Leibniz Research Centre for Working Environment and Human Factors, Dortmund, Germany.
Brain Stimul. 2021 Mar-Apr;14(2):316-326. doi: 10.1016/j.brs.2021.01.016. Epub 2021 Jan 28.
Transcranial direct current stimulation (tDCS), a neuromodulatory non-invasive brain stimulation technique, has shown promising results in basic and clinical studies. The known interindividual variability of the effects, however, limits the efficacy of the technique. Recently we reported neurophysiological effects of tDCS applied over the primary motor cortex at the group level, based on data from twenty-nine participants who received 15min of either sham, 0.5, 1.0, 1.5 or 2.0 mA anodal, or cathodal tDCS. The neurophysiological effects were evaluated via changes in: 1) transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEP), and 2) cerebral blood flow (CBF) measured by functional magnetic resonance imaging (MRI) via arterial spin labeling (ASL). At the group level, dose-dependent effects of the intervention were obtained, which however displayed interindividual variability.
In the present study, we investigated the cause of the observed inter-individual variability. To this end, for each participant, a MRI-based realistic head model was designed to 1) calculate anatomical factors and 2) simulate the tDCS- and TMS-induced electrical fields (EFs). We first investigated at the regional level which individual anatomical factors explained the simulated EFs (magnitude and normal component). Then, we explored which specific anatomical and/or EF factors predicted the neurophysiological outcomes of tDCS.
The results highlight a significant negative correlation between regional electrode-to-cortex distance (rECD) as well as regional CSF (rCSF) thickness, and the individual EF characteristics. In addition, while both rCSF thickness and rECD anticorrelated with tDCS-induced physiological changes, EFs positively correlated with the effects.
These results provide novel insights into the dependency of the neuromodulatory effects of tDCS on individual physical factors.
经颅直流电刺激（tDCS）是一种神经调节的非侵入性脑刺激技术，在基础和临床研究中显示出了良好的效果。然而，其效果的个体间可变性限制了该技术的疗效。最近，我们根据 29 名参与者的数据，报告了在初级运动皮层上应用 tDCS 的神经生理学效应，这些参与者接受了 15 分钟的假刺激、0.5、1.0、1.5 或 2.0 mA 阳极、或阴极 tDCS。神经生理学效应通过以下变化进行评估：1）经颅磁刺激（TMS）诱导的运动诱发电位（MEP），以及 2）通过动脉自旋标记（ASL）功能磁共振成像（MRI）测量的脑血流（CBF）。在组水平上，获得了干预的剂量依赖性效应，但显示出个体间的可变性。
在本研究中，我们调查了观察到的个体间可变性的原因。为此，为每个参与者设计了一个基于 MRI 的逼真头部模型，以 1）计算解剖因素，以及 2）模拟 tDCS 和 TMS 诱导的电场（EFs）。我们首先在区域水平上调查了哪些个体解剖因素解释了模拟的 EFs（幅度和法向分量）。然后，我们探索了哪些特定的解剖和/或 EF 因素预测了 tDCS 的神经生理学结果。
结果突出显示了局部电极-皮层距离（rECD）以及局部脑脊液（rCSF）厚度与个体 EF 特征之间的显著负相关。此外，虽然 rCSF 厚度和 rECD 与 tDCS 诱导的生理变化呈负相关，但 EFs 与效应呈正相关。
这些结果为 tDCS 的神经调节效果对个体物理因素的依赖性提供了新的见解。
