Department of Psychology, New York University, New York, NY, 10003, USA.
NYUAD Institute, New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, UAE.
Sci Rep. 2021 Jan 8;11(1):97. doi: 10.1038/s41598-020-79640-0.
Speech is a complex and ambiguous acoustic signal that varies significantly within and across speakers. Despite the processing challenge that such variability poses, humans adapt to systematic variations in pronunciation rapidly. The goal of this study is to uncover the neurobiological bases of the attunement process that enables such fluent comprehension. Twenty-four native English participants listened to words spoken by a "canonical" American speaker and two non-canonical speakers, and performed a word-picture matching task, while magnetoencephalography was recorded. Non-canonical speech was created by including systematic phonological substitutions within the word (e.g. [s] → [sh]). Activity in the auditory cortex (superior temporal gyrus) was greater in response to substituted phonemes, and, critically, this was not attenuated by exposure. By contrast, prefrontal regions showed an interaction between the presence of a substitution and the amount of exposure: activity decreased for canonical speech over time, whereas responses to non-canonical speech remained consistently elevated. Grainger causality analyses further revealed that prefrontal responses serve to modulate activity in auditory regions, suggesting the recruitment of top-down processing to decode non-canonical pronunciations. In sum, our results suggest that the behavioural deficit in processing mispronounced phonemes may be due to a disruption to the typical exchange of information between the prefrontal and auditory cortices as observed for canonical speech.
语音是一种复杂且模糊的声学信号，在说话者之间和内部都存在很大的差异。尽管这种可变性带来了处理上的挑战，但人类能够迅速适应发音的系统性变化。本研究的目的是揭示使这种流畅理解成为可能的调谐过程的神经生物学基础。24 名以英语为母语的参与者听了一位“标准”美国说话者和两位非标准说话者所说的单词，并进行了单词-图片匹配任务，同时记录了脑磁图。非标准语音是通过在单词中包含系统的语音替代（例如，[s]→[sh]）来创建的。听觉皮层（颞上回）对替代音的反应更强，关键是，这种反应不会因暴露而减弱。相比之下，前额叶区域显示出替代音的存在和暴露量之间的相互作用：随着时间的推移，对标准语音的活动减少，而对非标准语音的反应则持续升高。格拉格因果分析进一步表明，前额叶反应有助于调节听觉区域的活动，表明为了解码非标准发音而采用了自上而下的处理。总之，我们的结果表明，处理发音错误的音素的行为缺陷可能是由于典型的前额叶和听觉皮层之间信息交换的中断，这种情况在标准语音中也观察到了。
