Department of Neurology & Stroke, and Hertie Institute for Clinical Brain Research, University of Tübingen, Germany.
Center for Biomedical Imaging and Neuromodulation, Nathan Kline Institute for Psychiatric Research Orangeburg, NY, USA; Center for the Developing Brain, Child Mind Institute New York, NY, USA.
Brain Stimul. 2017 Nov-Dec;10(6):1061-1069. doi: 10.1016/j.brs.2017.07.010. Epub 2017 Jul 27.
Transcranial direct current stimulation (tDCS) can polarize the cortex of the human brain.
OBJECTIVE/HYPOTHESIS: We sought to verify the hypothesis that posterior-anterior (PA) but not anterior-posterior (AP) tDCS of primary motor cortex (M1) produces cooperative effects with corticospinal plasticity induced by paired associative stimulation of the supplementary motor area (SMA) to M1 projection (PAS) in a highly controlled experimental design.
Three experimental conditions were tested in a double-blinded, randomized crossover design in 15 healthy adults: Navigated PAS during PA-tDCS (35 cm electrodes, anode 3 cm posterior to M1 hand area, cathode over contralateral frontopolar cortex, 1 mA, 2 × 5 min) or AP-tDCS (reversed polarity), or sham-tDCS. Effects were analyzed over 120 min post-intervention by changes of motor evoked potential (MEP) amplitude in a hand muscle.
There was no significant effect of tDCS on PAS induced plasticity in the repeated-measures ANOVA. However, post-hoc within-subject contrasts revealed a significant tDCS with PAS interaction. This was explained by PA-tDCS and AP-tDCS modifying the PAS effect into the same direction in 13/15 subjects (87%, p = 0.004 for deviation from equality). Sizes of the PA-tDCS and AP-tDCS effects were correlated (r = 0.53, p = 0.044). A control experiment demonstrated that PA-tDCS and AP-tDCS alone (without PAS) had no effect on MEP amplitude.
Data point to unidirectional tDCS effects on PAS induced plasticity irrespective of tDCS polarity, in contrast to our hypothesis. We propose that radial symmetry of cortical columns, gyral geometry of motor cortex, and cooperativity of plasticity induction can explain the findings.
经颅直流电刺激（tDCS）可以使人类大脑皮层产生极化。
目的/假设：我们试图验证这样一个假设，即在后前（PA）而不是前后（AP）刺激初级运动皮层（M1）时，tDCS 与由补充运动区（SMA）到 M1 投射（PAS）的配对关联刺激诱导的皮质脊髓可塑性产生协同效应，这是在高度控制的实验设计中进行的。
在 15 名健康成年人的双盲、随机交叉设计中，测试了三种实验条件：在导航 PAS 期间进行 PA-tDCS（35cm 电极，阳极位于 M1 手区后 3cm，阴极位于对侧额极皮质，1mA，2×5min）或 AP-tDCS（反转极性）或假 tDCS。通过手部肌肉运动诱发电位（MEP）幅度的变化，在干预后 120min 分析效果。
在重复测量方差分析中，tDCS 对 PAS 诱导的可塑性没有显著影响。然而，事后的主体内对比揭示了 tDCS 与 PAS 的显著相互作用。这可以解释为在 13/15 名受试者中，PA-tDCS 和 AP-tDCS 将 PAS 效应改变为相同的方向（偏离相等的 p=0.004）。PA-tDCS 和 AP-tDCS 效应的大小相关（r=0.53，p=0.044）。一项对照实验表明，PA-tDCS 和 AP-tDCS 单独（无 PAS）对 MEP 幅度没有影响。
数据表明，无论 tDCS 极性如何，tDCS 对 PAS 诱导的可塑性都有单向影响，这与我们的假设相反。我们提出，皮质柱的径向对称性、运动皮层的回状几何形状和可塑性诱导的协同性可以解释这些发现。
