Wiethoff Sarah, Hamada Masashi, Rothwell John C
Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK.
Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK; Department of Neurology, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
Brain Stimul. 2014 May-Jun;7(3):468-75. doi: 10.1016/j.brs.2014.02.003. Epub 2014 Feb 15.
Responses to a number of different plasticity-inducing brain stimulation protocols are highly variable. However there is little data available on the variability of response to transcranial direct current stimulation (TDCS).
We tested the effects of TDCS over the motor cortex on corticospinal excitability. We also examined whether an individual's response could be predicted from measurements of onset latency of motor evoked potential (MEP) following stimulation with different orientations of monophasic transcranial magnetic stimulation (TMS).
Fifty-three healthy subjects participated in a crossover-design. Baseline latency measurements with different coil orientations and MEPs were recorded from the first dorsal interosseous muscle prior to the application of 10 min of 2 mA TDCS (0.057 mA/cm2). Thirty MEPs were measured every 5 min for up to half an hour after the intervention to assess after-effects on corticospinal excitability.
Anodal TDCS at 2 mA facilitated MEPs whereas there was no significant effect of 2 mA cathodal TDCS. A two-step cluster analysis suggested that approximately 50% individuals had only a minor, or no response to TDCS whereas the remainder had a facilitatory effect to both forms of stimulation. There was a significant correlation between the latency difference of MEPs (anterior-posterior stimulation minus latero-medial stimulation) and the response to anodal, but not cathodal TDCS.
The large variability in response to these TDCS protocols is in line with similar studies using other forms of non-invasive brain stimulation. The effects highlight the need to develop more robust protocols, and understand the individual factors that determine responsiveness.
对多种不同的可塑性诱导脑刺激方案的反应高度可变。然而，关于经颅直流电刺激（TDCS）反应变异性的数据很少。
我们测试了运动皮质上TDCS对皮质脊髓兴奋性的影响。我们还研究了是否可以通过测量单相经颅磁刺激（TMS）不同方向刺激后运动诱发电位（MEP）的起始潜伏期来预测个体的反应。
53名健康受试者参与了交叉设计。在施加10分钟2 mA TDCS（0.057 mA/cm2）之前，从第一背侧骨间肌记录不同线圈方向的基线潜伏期测量值和MEP。干预后每5分钟测量30次MEP，持续半小时，以评估对皮质脊髓兴奋性的后效应。
2 mA的阳极TDCS促进了MEP，而2 mA的阴极TDCS没有显著影响。两步聚类分析表明，约50%的个体对TDCS只有轻微或无反应，而其余个体对两种刺激形式均有促进作用。MEP潜伏期差异（前后刺激减去内外侧刺激）与阳极TDCS的反应之间存在显著相关性，但与阴极TDCS无关。
对这些TDCS方案反应的巨大变异性与使用其他形式非侵入性脑刺激的类似研究一致。这些效应凸显了制定更稳健方案以及了解决定反应性的个体因素的必要性。
