BACKGROUND Cognitive control (CC) is an important prerequisite for goal-directed behaviour and efficient information processing. Impaired CC is associated with reduced prefrontal cortex activity and various mental disorders, but may be effectively tackled by transcranial direct current stimulation (tDCS)-enhanced training. However, study data are inconsistent as efficacy depends on stimulation parameters whose implementations vary widely between studies. OBJECTIVE We systematically tested various tDCS parameter effects (anodal/cathodal polarity, 1/2 mA stimulation intensity, left/right prefrontal cortex hemisphere) on a six-session CC training combined with tDCS. METHODS Nine groups of healthy humans (male/female) received either anodal/cathodal tDCS of 1/2 mA over the left/right PFC or sham stimulation, simultaneously with a CC training (modified adaptive Paced Auditory Serial Addition Task [PASAT]). Subjects trained thrice per week (19 minutes each) for two weeks. We assessed performance progress in the PASAT before, during, and after training. Using a hierarchical approach, we incrementally narrowed down on optimal stimulation parameters supporting CC. Long-term CC effects as well as transfer effects in a flanker task were assessed after the training period as well as three months later. RESULTS Compared to sham stimulation, anodal but not cathodal tDCS improved performance gains. This was only valid for 1 mA stimulation intensity and particularly detected when applied to the left PFC. CONCLUSIONS Our results confirm beneficial, non-linear effects of anodal tDCS on cognitive training in a large sample of healthy subjects. The data consolidate the basis for further development of functionally targeted tDCS, supporting cognitive control training in mental disorders and guiding further development of clinical interventions.

中文翻译：

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认知控制训练和经颅直流电刺激：一种系统的优化方法

背景认知控制（CC）是目标导向行为和有效信息处理的重要前提。CC 受损与前额叶皮层活动减少和各种精神障碍有关，但可以通过经颅直流电刺激 (tDCS) 增强训练有效解决。然而，研究数据是不一致的，因为功效取决于刺激参数，其实施在研究之间差异很大。目标我们系统地测试了六节 CC 训练结合 tDCS 的各种 tDCS 参数效应（阳极/阴极极性、1/2 mA 刺激强度、左/右前额叶皮层半球）。方法 九组健康人（男性/女性）在左侧/右侧 PFC 或假刺激上接受 1/2 mA 的阳极/阴极 tDCS，同时进行 CC 训练（修改后的自适应节奏听觉序列添加任务 [PASAT]）。受试者每周训练三次（每次 19 分钟），持续两周。我们在训练前、训练中和训练后评估了 PASAT 的表现进展。使用分层方法，我们逐步缩小支持 CC 的最佳刺激参数。在训练期后以及三个月后评估了长期 CC 效果以及侧翼任务中的转移效果。结果 与假刺激相比，阳极而非阴极 tDCS 提高了性能增益。这仅对 1 mA 刺激强度有效，尤其是在应用于左侧 PFC 时检测到。结论 我们的结果证实了阳极 tDCS 对大量健康受试者的认知训练的有益的非线性影响。