Luque-Casado Antonio, Rodríguez-Freiría Rocío, Fogelson Noa, Iglesias-Soler Eliseo, Fernández-Del-Olmo Miguel
Area of Sport Sciences, Faculty of Sports Sciences and Physical Education, Center for Sport Studies, King Juan Carlos University, Madrid, Spain.
Department of Physical Education and Sport, Faculty of Sports Sciences and Physical Education, University of A Coruna, Performance and Health Group, A Coruña, Spain.
Neuroscience. 2020 Sep 1;443:120-130. doi: 10.1016/j.neuroscience.2020.07.036. Epub 2020 Jul 28.
Despite the growing interest in the use of transcranial direct current stimulation (tDCS) for the modulation of human cognitive function, there are contradictory findings regarding the cognitive benefits of this technique. Inter-individual response variability to tDCS may play a significant role. We explored the effects of anodal versus sham tDCS over the left prefrontal cortex (LPFC) on working memory performance, taking into account the inter-individual variability. Twenty-nine healthy volunteers received an 'offline' anodal tDCS (1.5 mA, 15 min) to the left prefrontal cortex (F3 electrode site) in an intra-individual, cross-over, sham-controlled experimental design. n-back and Sternberg task performance was assessed before (baseline), immediately after tDCS administration (T1) and 5 min post-T1 (T2). We applied an integrative clustering approach to characterize both the group and individual responses to tDCS, as well as identifying naturally occurring subgroups that may be present within the total sample. Anodal tDCS failed to improve working memory performance in the total sample. Cluster analysis identified a subgroup of 'responders' who significantly improved their performance after anodal (vs. sham) stimulation, although not to a greater extent than the best baseline or sham condition. The proportion of 'responders' ranged from 15% to 59% across task conditions and behavioral outputs. Our findings show a high inter-individual variability of the tDCS response, suggesting that the use of tCDS may not be an effective tool to improve working memory performance in healthy subjects. We propose that the use of clustering methods is more suitable in identifying 'responders' and for evaluating the efficacy of this technique.
尽管人们对使用经颅直流电刺激（tDCS）来调节人类认知功能的兴趣日益浓厚，但关于该技术的认知益处仍存在相互矛盾的研究结果。个体对tDCS的反应变异性可能起着重要作用。我们探讨了阳极tDCS与假刺激tDCS作用于左侧前额叶皮质（LPFC）对工作记忆表现的影响，并考虑了个体间的变异性。29名健康志愿者在个体内、交叉、假刺激对照的实验设计中，接受了对左侧前额叶皮质（F3电极部位）的“离线”阳极tDCS（1.5毫安，15分钟）。在tDCS给药前（基线）、给药后立即（T1）以及T1后5分钟（T2）评估n-back和斯特恩伯格任务表现。我们应用综合聚类方法来表征群体和个体对tDCS的反应，以及识别总样本中可能存在的自然形成的亚组。阳极tDCS未能改善总样本的工作记忆表现。聚类分析确定了一个“反应者”亚组，他们在接受阳极（与假刺激相比）刺激后表现显著改善，尽管改善程度不超过最佳基线或假刺激条件。在不同任务条件和行为输出中，“反应者”的比例在15%至59%之间。我们的研究结果表明，tDCS反应存在高度的个体间变异性，这表明在健康受试者中使用tCDS可能不是提高工作记忆表现的有效工具。我们建议使用聚类方法更适合识别“反应者”并评估该技术的疗效。
