Previous behavioural and neuroimaging research suggested distinct cortical systems involved in processing abstract and concrete semantics; however, there is a dearth of causal evidence to support this. To address this, we applied anodal, cathodal, or sham (placebo) tDCS over Wernicke’s area before a session of contextual learning of novel concrete and abstract words (n = 10 each), presented five times in short stories. Learning effects were assessed at lexical and semantic levels immediately after the training and, to attest any consolidation effects of overnight sleep, on the next day. We observed successful learning of all items immediately after the session, with decreased performance in Day 2 assessment. Importantly, the results differed between stimulation conditions and tasks. Whereas the accuracy of semantic judgement for abstract words was significantly lower in the sham and anodal groups on Day 2 vs. Day 1, no significant performance drop was observed in the cathodal group. Similarly, the cathodal group showed no significant overnight performance reduction in the free recall task for either of the stimuli, unlike the other two groups. Furthermore, between-group analysis showed an overall better performance of both tDCS groups over the sham group, particularly expressed for abstract semantics and cathodal stimulation. In sum, the results suggest overlapping but diverging brain mechanisms for concrete and abstract semantics and indicate a larger degree of involvement of core language areas in storing abstract knowledge. Furthermore, they demonstrate a possiblity to improve learning outcomes using neuromodulatory techniques.

先前的行为和神经影像学研究表明，处理抽象和具体语义的过程中涉及不同的皮层系统；然而，缺乏因果证据支持这一点。为了解决这个问题，我们在 Wernicke 区域应用了阳极、阴极或假（安慰剂）tDCS，然后进行了新的具体和抽象单词（每个 n = 10）的上下文学习，在短篇小说中出现了五次。训练后立即在词汇和语义层面评估学习效果，并在第二天证明过夜睡眠的任何巩固效果。我们在课程结束后立即观察到所有项目的成功学习，第 2 天评估的表现有所下降。重要的是，刺激条件和任务之间的结果不同。与第 1 天相比，第 2 天假组和阳极组抽象词语义判断的准确性显着降低，阴极组没有观察到显着的性能下降。类似地，与其他两组不同，阴极组在任何一种刺激的自由回忆任务中都没有表现出显着的过夜表现下降。此外，组间分析显示，两个 tDCS 组的整体性能优于假组，尤其是在抽象语义和阴极刺激方面。总之，结果表明具体和抽象语义的大脑机制重叠但发散，并表明核心语言区域在存储抽象知识方面有更大程度的参与。此外，