Abstract：
Neuromodulation with transcranial direct current stimulation (tDCS) can transiently alter neural activity, but its spatial precision is low. High-definition (HD) tDCS was introduced to increase spatial precision by placing additional electrodes over the scalp. Initial evaluations of HD tDCS indicated polarity-specific neurophysiological effects-similar to conventional tDCS albeit with greater spatial precision. Here, we compared the effects of cathodal tDCS or HD tDCS in a 4 × 1 configuration over prefrontal cortex (PFC) regions on behavioural outcomes in a magnitude classification task. We report results on overall performance, on the numerical distance effect as a measure of numerical processing, and on the spatial-numerical associations of response codes (SNARC) effect, which was previously affected by prefrontal tDCS. Healthy volunteers (n = 68) received sham or cathodal HD tDCS at 1 mA over the left dorsolateral prefrontal cortex (DLPFC) or the left inferior frontal gyrus (IFG). Results were compared to an identical protocol with conventional cathodal tDCS to the left PFC versus sham (n = 64). Mixed effects models showed performance gains relative to sham tDCS in all conditions after tDCS (i.e. \'offline\'), whereas montages over PFC and DLPFC already showed performance gains during tDCS (i.e. \'online\'). In contrast to conventional tDCS, HD tDCS did not reduce the SNARC effect. Neither condition affected numerical processing, as expected. The results suggest that HD tDCS with cathodal polarity might require further adjustments (i.e. regarding tDCS intensity) for effective modulations of cognitive-behavioural performance, which could be achieved by individualised current density in electric field modelling.
摘要：
经颅直流电刺激（tDCS）的神经调节可以短暂改变神经活动，但其空间精度较低。引入高清晰度（HD）tDCS，通过在头皮上放置额外的电极来提高空间精度。对HDtDCS的初步评估表明，极性特定的神经生理效应与常规tDCS相似，尽管具有更大的空间精度。这里,我们比较了4×1配置的阴极tDCS或HDtDCS在前额叶皮层(PFC)区域对震级分类任务中行为结局的影响.我们报告总体表现的结果，关于数值距离效应作为数值处理的度量，以及响应代码(SNARC)效应的空间-数值关联，以前受到前额叶tDCS的影响。健康志愿者（n=68）在左背外侧前额叶皮层（DLPFC）或左额下回（IFG）上以1mA接受假或阴极HDtDCS。将结果与具有常规阴极tDCS的相同方案与左侧PFC与假手术(n=64)进行比较。混合效应模型在tDCS后的所有条件下显示相对于假tDCS的性能增益(即“离线”)，而相对于PFC和DLPFC的蒙太奇在tDCS期间已经显示出性能提升(即\'在线\')。与传统的tDCS相比，HDtDCS没有降低SNARC效应。两种条件都不影响数值加工，如预期。结果表明，具有阴极极性的HDtDCS可能需要进一步调整（即关于tDCS强度）以有效调节认知行为表现，这可以通过电场建模中的个性化电流密度来实现。
