Laboratory of Behavioural Neurodynamics, Saint Petersburg University, Saint Petersburg, 199004, Russian Federation.
Center of Functionally Integrative Neuroscience (CFIN), Department of Clinical Medicine, Aarhus University, 8000, Aarhus, Denmark.
Sci Rep. 2021 Jan 15;11(1):1508. doi: 10.1038/s41598-020-79967-8.
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涉及到不同的皮质系统；然而，目前缺乏支持这一观点的因果证据。为了解决这个问题，我们在一次新的具体和抽象单词语境学习（n=10 个）之前，应用经颅直流电刺激（tDCS）对韦尼克区进行阳极、阴极或假刺激（安慰剂），这些单词在短故事中呈现五次。学习效果在训练后立即在词汇和语义水平上进行评估，并在第二天评估任何巩固效果。我们观察到所有项目在课程结束后立即成功学习，第二天的评估表现下降。重要的是，结果因刺激条件和任务而异。虽然在第二天，与第一天相比，假刺激和阳极刺激组对抽象单词的语义判断准确性显著降低，但阴极刺激组没有观察到显著的性能下降。同样，与其他两组不同的是，阴极组在自由回忆任务中对两种刺激的夜间表现都没有明显下降。此外，组间分析显示，两个 tDCS 组的表现均优于假刺激组，特别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既有重叠又有分歧，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，它们还表明使用神经调节技术有可能提高学习效果。
