Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom.
Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom; School of Psychology, University of Nottingham, Nottingham, United Kingdom.
Cortex. 2018 Jun;103:44-54. doi: 10.1016/j.cortex.2018.02.007. Epub 2018 Feb 22.
Comprehending speech can be particularly challenging in a noisy environment and in the absence of semantic context. It has been proposed that the articulatory motor system would be recruited especially in difficult listening conditions. However, it remains unknown how signal-to-noise ratio (SNR) and semantic context affect the recruitment of the articulatory motor system when listening to continuous speech. The aim of the present study was to address the hypothesis that involvement of the articulatory motor cortex increases when the intelligibility and clarity of the spoken sentences decreases, because of noise and the lack of semantic context. We applied Transcranial Magnetic Stimulation (TMS) to the lip and hand representations in the primary motor cortex and measured motor evoked potentials from the lip and hand muscles, respectively, to evaluate motor excitability when young adults listened to sentences. In Experiment 1, we found that the excitability of the lip motor cortex was facilitated during listening to both semantically anomalous and coherent sentences in noise relative to non-speech baselines, but neither SNR nor semantic context modulated the facilitation. In Experiment 2, we replicated these findings and found no difference in the excitability of the lip motor cortex between sentences in noise and clear sentences without noise. Thus, our results show that the articulatory motor cortex is involved in speech processing even in optimal and ecologically valid listening conditions and that its involvement is not modulated by the intelligibility and clarity of speech.
理解言语在嘈杂的环境中和缺乏语义上下文的情况下特别具有挑战性。有人提出，在困难的听力条件下，发音运动系统会被招募。然而，当听连续的言语时，信号噪声比（SNR）和语义上下文如何影响发音运动系统的招募仍然未知。本研究的目的是检验以下假设：当由于噪声和缺乏语义上下文而导致言语的可理解性和清晰度降低时，发音运动皮层的参与度会增加。我们应用经颅磁刺激（TMS）对初级运动皮层的嘴唇和手部代表区进行刺激，并分别测量嘴唇和手部肌肉的运动诱发电位，以评估年轻人在听句子时的运动兴奋性。在实验 1 中，我们发现与非言语基线相比，年轻人在噪声中听语义异常和连贯的句子时，嘴唇运动皮层的兴奋性均得到增强，但 SNR 和语义上下文均未调节这种增强。在实验 2 中，我们复制了这些发现，并且在噪声中的句子和无噪声的清晰句子之间，嘴唇运动皮层的兴奋性没有差异。因此，我们的结果表明，即使在最佳和生态有效的听力条件下，发音运动皮层也参与言语处理，并且其参与程度不受言语的可理解性和清晰度的调节。
