Goregliad Fjaellingsdal Tatiana, Ruigendijk Esther, Scherbaum Stefan, Bleichner Martin G
Department of Psychology, European Medical School, University of Oldenburg Oldenburg, Germany.
Cluster of Excellence Hearing4all, University of OldenburgOldenburg, Germany; Department of Dutch, University of OldenburgOldenburg, Germany.
Front Psychol. 2016 Nov 28;7:1854. doi: 10.3389/fpsyg.2016.01854. eCollection 2016.
Language occurs naturally in conversations. However, the study of the neural underpinnings of language has mainly taken place in single individuals using controlled language material. The interactive elements of a conversation (e.g., turn-taking) are often not part of neurolinguistic setups. The prime reason is the difficulty to combine open unrestricted conversations with the requirements of neuroimaging. It is necessary to find a trade-off between the naturalness of a conversation and the restrictions imposed by neuroscientific methods to allow for ecologically more valid studies. Here, we make an attempt to study the effects of a conversational element, namely turn-taking, on linguistic neural correlates, specifically the N400 effect. We focus on the physiological aspect of turn-taking, the speaker-switch, and its effect on the detectability of the N400 effect. The N400 event-related potential reflects expectation violations in a semantic context; the N400 effect describes the difference of the N400 amplitude between semantically expected and unexpected items. Sentences with semantically congruent and incongruent final words were presented in two turn-taking modes: (1) reading aloud first part of the sentence and listening to speaker-switch for the final word, and (2) listening to first part of the sentence and speaker-switch for the final word. A significant N400 effect was found for both turn-taking modes, which was not influenced by the mode itself. However, the mode significantly affected the P200, which was increased for the reading aloud mode compared to the listening mode. Our results show that an N400 effect can be detected during a speaker-switch. Speech articulation (reading aloud) before the analyzed sentence fragment did also not impede the N400 effect detection for the final word. The speaker-switch, however, seems to influence earlier components of the electroencephalogram, related to processing of salient stimuli. We conclude that the N400 can effectively be used to study neural correlates of language in conversational approaches including speaker-switches.
语言自然地出现在对话中。然而，对语言神经基础的研究主要是在个体身上使用受控语言材料进行的。对话中的互动元素（如轮流发言）通常不属于神经语言学研究设置的一部分。主要原因是难以将开放式无限制对话与神经成像的要求相结合。有必要在对话的自然性和神经科学方法所施加的限制之间找到一种平衡，以进行生态学上更有效的研究。在这里，我们试图研究对话元素——轮流发言，对语言神经关联，特别是N400效应的影响。我们关注轮流发言的生理方面，即说话者转换，及其对N400效应可检测性的影响。N400事件相关电位反映语义背景下的预期违背；N400效应描述了语义预期和意外项目之间N400波幅的差异。语义一致和不一致的结尾词的句子以两种轮流发言模式呈现：（1）大声朗读句子的第一部分并听说话者转换以获取结尾词，以及（2）听句子的第一部分并听说话者转换以获取结尾词。两种轮流发言模式都发现了显著的N400效应，且不受模式本身的影响。然而，该模式对P200有显著影响，与聆听模式相比，大声朗读模式下的P200有所增加。我们的结果表明，在说话者转换期间可以检测到N400效应。在所分析的句子片段之前的言语表达（大声朗读）也不妨碍对结尾词的N400效应检测。然而，说话者转换似乎会影响脑电图的早期成分，这与突出刺激的处理有关。我们得出结论，N400可以有效地用于研究包括说话者转换在内的对话方式中语言神经关联。
