Left Inferior Frontal Gyrus Sensitivity to Phonetic Competition in Receptive Language Processing: A Comparison of Clear and Conversational Speech.
Left Inferior Frontal Gyrus Sensitivity to Phonetic Competition in Receptive Language Processing: A Comparison of Clear and Conversational Speech.
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DOI：
10.1162/jocn_a_01208
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发表时间：
2018-03
影响因子：
3.2
通讯作者：
Myers E
中科院分区：
文献类型：
--
作者：
Xie X;Myers E
语音信号充满了语音歧义的变化。例如，当说话者用会话语域说话时，他们的发音精度较低，与清晰的言语语域相比，在语音层面上更容易造成混淆。目前的心理语言学模型假设，模棱两可的语音激活了不止一个语音类别，并且词汇前水平的竞争级联到词汇处理水平。成像研究表明，左侧额下回（LIFG）受到同时激活的类别之间的语音竞争的调节，对更模糊的标记的激活增加。然而，这些研究经常使用人为操纵的语音和/或元语言任务，这可能会招募对自然语音识别不重要的神经区域。事实上，一个著名的语音处理模型，双流模型，假设前颞叶颞叶不参与接受性语言处理中的词汇前处理。在本研究中，我们利用语音信号中语音竞争的自然变化来研究听者在接受性语言任务中对语音竞争敏感的神经系统。研究人员用功能磁共振成像（fMRI）监测参与者的神经活动，并让他们听到以清晰或对话的方式说出的无意义句子。根据元音易混淆性的测量，会话句子包含更大的语音竞争，这些句子也会在LIFG的一个区域引起更大的激活。句子级语音竞争指标与LIFG活动也有独特的相关性。这一发现与LIFG在多个语言处理层面对竞争做出反应的假设是一致的，并且该区域的招募不需要明确的语音判断。
The speech signal is rife with variations in phonetic ambiguity. For instance, when talkers speak in a conversational register, they demonstrate less articulatory precision, leading to greater potential for confusability at the phonetic level compared to a clear speech register. Current psycholinguistic models assume that ambiguous speech sounds activate more than one phonological category, and that competition at prelexical levels cascades to lexical levels of processing. Imaging studies have shown that the left inferior frontal gyrus (LIFG) is modulated by phonetic competition between simultaneously activated categories, with increases in activation for more ambiguous tokens. Yet these studies have often used artificially manipulated speech and/or metalinguistic tasks, which arguably may recruit neural regions that are not critical for natural speech recognition. Indeed, a prominent model of speech processing, the Dual Stream Model, posits that the LIFG is not involved in prelexical processing in receptive language processing. In the current study, we exploited natural variation in phonetic competition in the speech signal in order to investigate the neural systems sensitive to phonetic competition as listeners engaged in a receptive language task. Participants heard nonsense sentences spoken in either a clear or conversational register as neural activity was monitored using fMRI. Conversational sentences contained greater phonetic competition, as estimated by measures of vowel confusability, and these sentences also elicited greater activation in a region in the LIFG. Sentence-level phonetic competition metrics uniquely correlated with LIFG activity as well. This finding is consistent with the hypothesis that the LIFG responds to competition at multiple levels of language processing, and that recruitment of this region does not require an explicit phonological judgment.
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