Laboratory of Behavioural Neurodynamics, St. Petersburg State University, 199034 St. Petersburg, Russia.
Laboratory of Behavioural Neurodynamics, St. Petersburg State University, 199034 St. Petersburg, Russia.
Neurobiol Learn Mem. 2022 Jul;192:107622. doi: 10.1016/j.nlm.2022.107622. Epub 2022 Apr 21.
Broca's area in the left hemisphere of the human neocortex has been suggested as a major hub for acquisition, storage, and access of linguistic information, abstract words in particular. Direct causal evidence for the latter, however, is still scarce; filling this gap was the goal of the present study. Using transcranial direct current stimulation (tDCS) of Broca's region, we aimed to delineate the involvement of this area in abstract and concrete word acquisition. The experiment used a between-subject design and involved 15 min of anodal or cathodal tDCS over Broca's area, or a sham/placebo control condition. The stimulation procedure was followed by a contextual learning session, in which participants were exposed to new concrete and abstract words embedded into short five-sentence texts. Finally, a set of behavioural assessment tasks was run to assess the learning outcomes immediately after the training (Day 1) and with a 24-hour delay (Day 2). The results showed that participants recognised novel abstract words more accurately after both anodal and cathodal tDCS in comparison with the sham condition on Day 1, which was also accompanied by longer recognition times (presumably due to deeper lexico-semantic processing), supporting the role of Broca's region in acquisition of abstract semantics. They were also more successful when recalling concrete words after cathodal tDCS, which indicates a degree of Broca's area involvement in forming memory circuits for concrete words as well. A decrease in the accuracy of recall of word forms and their meanings, as well as in recognition, was observed for all stimulation groups and both types of semantics on Day 2. The results suggest that both anodal and cathodal tDCS of Broca's area improves immediate contextual learning of novel vocabulary, predominantly affecting abstract semantics.
左半脑额下回区域被认为是人类新皮质中获取、存储和获取语言信息（尤其是抽象词汇）的主要枢纽。然而，关于后者的直接因果证据仍然很少；本研究旨在填补这一空白。本研究采用经颅直流电刺激（tDCS）刺激布洛卡区，旨在描绘该区域在抽象和具体词汇习得中的作用。实验采用了被试间设计，包括 15 分钟的左脑额下回区阳极或阴极 tDCS 刺激，或假刺激/安慰剂对照条件。刺激过程后，进行语境学习，让参与者接触到嵌入在五个短句子中的新的具体和抽象单词。最后，进行了一组行为评估任务，以在训练后立即（第 1 天）和 24 小时后（第 2 天）评估学习结果。结果表明，与假刺激条件相比，第 1 天接受阳极和阴极 tDCS 刺激的参与者在识别新的抽象单词时更准确，而且识别时间更长（可能是由于词汇语义处理更深），这支持了布洛卡区在抽象语义习得中的作用。在阴极 tDCS 刺激后，参与者回忆具体单词的成功率也更高，这表明布洛卡区在形成具体单词的记忆回路方面也有一定的参与。在第 2 天，所有刺激组和两种语义类型的单词形式和含义的回忆准确性以及识别准确性都有所下降。研究结果表明，左脑额下回区的阳极和阴极 tDCS 刺激都可以提高新词汇的即时语境学习效果，主要影响抽象语义。
