Similarity measures, the extent to which two concepts have similar meanings, are the key to understand how concepts are represented, with different theoretical perspectives relying on very different sources of data from which similarity can be calculated. While there is some commonality in similarity measures, the extent of their correlation is limited. Previous studies also suggested that the relative performance of different similarity measures may also vary depending on concept concreteness and that the inferior parietal lobule (IPL) may be involved in the integration of conceptual features in a multimodal system for the semantic categorization. Here, we tested for the first time whether theory‐based similarity measures predict the pattern of brain activity in the IPL differently for abstract and concrete concepts. English speakers performed a semantic decision task, while we recorded their brain activity in IPL through fNIRS. Using representational similarity analysis, results indicated that the neural representational similarity in IPL conformed to the lexical co‐occurrence among concrete concepts (regardless of the hemisphere) and to the affective similarity among abstract concepts in the left hemisphere only, implying that semantic representations of abstract and concrete concepts are characterized along different organizational principles in the IPL. We observed null results for the decoding accuracy. Our study suggests that the use of the representational similarity analysis as a complementary analysis to the decoding accuracy is a promising tool to reveal similarity patterns between theoretical models and brain activity recorded through fNIRS.

中文翻译：

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顶下小叶对具体和抽象词的不同语义相似关系敏​​感

相似性度量，即两个概念具有相似含义的程度，是理解概念如何表示的关键，不同的理论观点依赖于可以计算相似性的非常不同的数据来源。虽然相似性度量有一些共性，但它们的相关程度是有限的。先前的研究还表明，不同相似性度量的相对性能也可能因概念具体性而异，并且顶下小叶（IPL）可能参与语义分类的多模态系统中概念特征的整合。在这里，我们首次测试了基于理论的相似性测量是否对抽象和具体概念的 IPL 中的大脑活动模式有不同的预测。说英语的人执行语义决策任务，而我们通过 fNIRS 在 IPL 中记录他们的大脑活动。使用表征相似性分析，结果表明 IPL 中的神经表征相似性符合具体概念之间的词汇共现（不考虑半球）和仅在左半球的抽象概念之间的情感相似性，这意味着抽象的语义表示IPL 中的不同组织原则对具体概念进行了表征。我们观察到解码精度的空结果。我们的研究表明，使用代表性相似性分析作为解码精度的补充分析是揭示理论模型和通过 fNIRS 记录的大脑活动之间的相似性模式的有前途的工具。