Neural discrimination of auditory contrasts is usually studied via the mismatch negativity (MMN) component of the event-related potentials. In the processing of speech contrasts, the magnitude of MMN is determined by both the acoustic as well as the phonological distance between stimuli. Also, the MMN can be modulated by the order in which the stimuli are presented, thus indexing perceptual asymmetries in speech sound processing. Here we assessed the MMN elicited by two types of phonological contrasts, namely vowel quality and vowel length, assuming that both will elicit a comparably strong MMN as both are phonemic in the listeners’ native language (Czech) and perceptually salient. Furthermore, we tested whether any of those phonemic contrasts is processed asymmetrically, and whether the asymmetries are acoustically or linguistically conditioned. The MMN elicited by the spectral change between /a/ and /ɛ/ was comparable to the MMN elicited by the durational change between /ɛ/ and /ɛː/, suggesting that both types of contrasts are equally important for Czech listeners. Furthermore, the spectral change in vowels yielded an asymmetrical pattern manifested by a larger MMN response to the change from /ɛ/ to /a/ than from /a/ to /ɛ/. The lack of such asymmetry in the MMN to the same spectral change in complex tones spoke against an acoustically-based explanation, indicating that it may instead have been the phonological properties of the vowels that triggered the asymmetry. The potential phonological origins of the asymmetry are discussed within an established framework, and conclusions are drawn about the perceptual relevance of the place and height features for the Czech /ɛ/-/a/ contrast.

中文翻译：

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语音和非语音刺激的频谱和持续时间变化的神经处理：一项针对捷克成年人的 MMN 研究

通常通过事件相关电位的失配负性 (MMN) 成分来研究听觉对比的神经辨别力。在语音对比的处理中，MMN 的大小由刺激之间的声学​​和语音距离决定。此外，MMN 可以通过呈现刺激的顺序进行调制，从而索引语音处理中的感知不对称。在这里，我们评估了由两种类型的音韵对比引起的 MMN，即元音质量和元音长度，假设两者都会引起比较强的 MMN，因为两者都是听者的母语（捷克语）中的音位并且在感知上是显着的。此外，我们测试了这些音位对比中的任何一个是否是不对称处理的，以及这些不对称是否受声学或语言条件的影响。/a/ 和 /ɛ/ 之间的频谱变化引起的 MMN 与 /ɛ/ 和 /ɛː/ 之间的持续变化引起的 MMN 相当，这表明两种类型的对比对捷克听众同样重要。此外，元音的频谱变化产生了不对称模式，表现为对从 /ɛ/ 到 /a/ 的变化比从 /a/ 到 /ɛ/ 的变化更大的 MMN 响应。MMN 中对于复杂音调的相同频谱变化缺乏这种不对称性，这与基于声学的解释相悖，这表明可能是元音的语音特性引发了不对称性。在既定框架内讨论了不对称的潜在音系起源，并得出了关于捷克语 /ɛ/-/a/ 对比的位置和高度特征的感知相关性的结论。