Yu Yan H, Shafer Valerie L
Department of Communication Sciences and Disorders, St. John's University, Queens, NY, United States.
The Graduate Center, City University of New York, New York, NY, United States.
Front Hum Neurosci. 2021 Apr 9;15:629517. doi: 10.3389/fnhum.2021.629517. eCollection 2021.
Many studies have observed modulation of the amplitude of the neural index mismatch negativity (MMN) related to which member of a phoneme contrast [phoneme A, phoneme B] serves as the frequent (standard) and which serves as the infrequent (deviant) stimulus (i.e., AAAB vs. BBBA) in an oddball paradigm. Explanations for this amplitude modulation range from acoustic to linguistic factors. We tested whether exchanging the role of the mid vowel /ε/ vs. high vowel /ɪ/ of English modulated MMN amplitude and whether the pattern of modulation was compatible with an underspecification account, in which the underspecified height values are [-high] and [-low]. MMN was larger for /ε/ as the deviant, but only when compared across conditions to itself as the standard. For the within-condition comparison, MMN was larger to /ɪ/ deviant minus /ε/ standard than to the reverse. A condition order effect was also observed. MMN amplitude was smaller to the deviant stimulus if it had previously served as the standard. In addition, the amplitudes of late discriminative negativity (LDN) showed similar asymmetry. LDN was larger for deviant /ε/ than deviant /ɪ/ when compared to themselves as the standard. These findings were compatible with an underspecification account, but also with other accounts, such as the Natural Referent Vowel model and a prototype model; we also suggest that non-linguistic factors need to be carefully considered as additional sources of speech processing asymmetries.
许多研究观察到，在奇偶数范式中，与音位对比[音位A、音位B]中的哪一个成员作为频繁（标准）刺激以及哪一个作为不频繁（偏差）刺激（即AAAB与BBBA）相关的神经指标失匹配负波（MMN）的幅度会受到调制。对这种幅度调制的解释范围从声学因素到语言因素。我们测试了交换英语中元音/ε/与高元音/ɪ/的角色是否会调制MMN幅度，以及调制模式是否与一种不完全指定解释相符，在该解释中，不完全指定的高度值为[-高]和[-低]。当/ε/作为偏差刺激时，MMN更大，但仅在跨条件与自身作为标准刺激进行比较时如此。对于条件内比较，/ɪ/偏差减去/ε/标准时的MMN大于相反情况。还观察到了条件顺序效应。如果偏差刺激先前曾作为标准刺激，其MMN幅度会更小。此外，晚期辨别负波（LDN）的幅度也表现出类似的不对称性。当与自身作为标准刺激进行比较时，偏差/ε/的LDN大于偏差/ɪ/的LDN。这些发现与不完全指定解释相符，但也与其他解释相符，如自然参照元音模型和原型模型；我们还建议，非语言因素需要作为语音处理不对称性的额外来源加以仔细考虑。
