Response variability following transcranial direct current stimulation (tDCS) highlights need for exploring different tDCS electrode montages. Corticospinal excitability (CSE), cortico-cortical excitability and intra-individual variability was compared following conventional and high-definition (HD) anodal (a-tDCS) and cathodal (c-tDCS) tDCS. Fifteen healthy males attended four sessions at-least one-week apart: conventional a-tDCS, conventional c-tDCS, HD-a-tDCS, HD-c-tDCS. TDCS was administered (1 mA, 10-minutes) over primary motor cortex (M1), via 6 x 4 cm active and 7 x 5 cm return electrodes (conventional tDCS) and 4 × 1 ring-electrodes 3.5 cm apart over M1 (HD-tDCS). For CSE, twenty-five single-pulse transcranial magnetic stimulation (TMS) peak-to-peak motor evoked potentials (MEP) were recorded at baseline, 0-minutes and 30-minutes post-tDCS. Twenty-five paired-pulse MEPs with 3-millisecond (ms) inter-pulse interval (IPI) and twenty-five at 10 ms assessed short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF). MEP standardised z-values standard deviations represented intra-individual variability. No significant changes in CSE from baseline were reported for all four interventions. No significant differences were reported in CSE between conventional and HD a-tDCS, but significant differences between conventional and HD c-tDCS 0-minutes post-tDCS. Conventional tDCS significantly reduced intra-individual variability compared to HD-tDCS for a-tDCS (0-minutes) and c-tDCS (30-minutes). No changes were reported for SICI/ICF. These novel findings of increased intra-individual variability following HD-tDCS, at the current stimulus parameters, highlight need for further nuanced research and refinement to optimise the HD-tDCS dosage-response relationship.

中文翻译：

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经颅直流电刺激对皮质脊髓和皮质皮质兴奋性和反应变异性的影响：传统与高清蒙太奇

经颅直流电刺激 (tDCS) 后的反应变异性凸显了探索不同 tDCS 电极蒙太奇的必要性。在常规和高清 (HD) 阳极 (a-tDCS) 和阴极 (c-tDCS) tDCS 之后，比较了皮质脊髓兴奋性 (CSE)、皮质-皮质兴奋性和个体内变异性。15 名健康男性参加了至少相隔一周的四次会议：常规 a-tDCS、常规 c-tDCS、HD-a-tDCS、HD-c-tDCS。通过 6 x 4 cm 主动电极和 7 x 5 cm 返回电极（传统 tDCS）和 4 x 1 环形电极在 M1（HD -tDCS）。对于 CSE，在基线、tDCS 后 0 分钟和 30 分钟记录了 25 次单脉冲经颅磁刺激 (TMS) 峰峰值运动诱发电位 (MEP)。具有 3 毫秒 (ms) 脉冲间间隔 (IPI) 的 25 个配对脉冲 MEP 和 10 ms 的 25 个配对脉冲 MEP 评估了短间隔皮质内抑制 (SICI) 和皮质内促进 (ICF)。MEP 标准化 z 值标准偏差表示个体内变异。所有四种干预措施均未报告 CSE 与基线相比的显着变化。传统和 HD a-tDCS 之间的 CSE 没有显着差异，但在 tDCS 后 0 分钟，传统和 HD c-tDCS 之间的 CSE 存在显着差异。与 HD-tDCS 相比，传统 tDCS 显着降低了 a-tDCS（0 分钟）和 c-tDCS（30 分钟）的个体内变异性。SICI/ICF 未报告任何变化。在当前的刺激参数下，HD-tDCS 后个体内变异性增加的这些新发现，