Rhodes Ryan, Han Chao, Hestvik Arild
Department of Linguistics and Cognitive Science, University of Delaware, Newark, DE, USA.
Atten Percept Psychophys. 2019 May;81(4):897-911. doi: 10.3758/s13414-019-01728-1.
We use a "varying standards" oddball paradigm and compare two phonetically differing conditions to find evidence that the auditory cortex has access to discrete phonological representations when making predictions about incoming speech sounds. Brain responses were recorded with a 128-electrode EEG system as subjects passively listened to synthetic speech sounds from a /dæ/-/tæ/ continuum. Deviant stimuli were compared to a control condition to obtain a mismatch negativity (MMN) response, indicative of a "surprise" at a stimulus that deviates from the memory trace. We tested two conditions with phonetically different varying standards - a "low-T" condition with VOT values of 60, 65, and 70 ms, and a "high-T" condition with VOT values of 75, 80, and 85 ms. The amplitude of the mismatch response is generally sensitive to acoustic distance. If the memory trace generated by the auditory cortex contains phonetic information about the standards, then a difference in mismatch amplitude is expected. However, if a phonological memory trace is used, every standard will be represented identically and no difference in mismatch amplitude will be observed. We found no distance effect in our results, indicating an absence of fine-grained phonetic information. This supports the claim that the auditory cortex has access to phonological category representations.
我们使用一种“变化标准”的异常刺激范式，比较两种语音不同的条件，以寻找证据表明听觉皮层在对传入语音进行预测时能够获取离散的音位表征。当受试者被动聆听来自/dæ/-/tæ/连续体的合成语音时，用128电极脑电图系统记录大脑反应。将异常刺激与对照条件进行比较，以获得失配负波（MMN）反应，这表明对偏离记忆痕迹的刺激会产生“惊讶”。我们测试了两种语音不同的变化标准条件——一种“低T”条件，其VOT值为60、65和70毫秒，以及一种“高T”条件，其VOT值为75、80和85毫秒。失配反应的幅度通常对声学距离敏感。如果听觉皮层产生的记忆痕迹包含有关标准的语音信息，那么预计失配幅度会有差异。然而，如果使用音位记忆痕迹，每个标准将以相同的方式表示，并且不会观察到失配幅度的差异。我们在结果中未发现距离效应，这表明不存在细粒度的语音信息。这支持了听觉皮层能够获取音位类别表征的说法。
