Department of Speech and Hearing Sciences, University of Washington, 1417 NE 42nd Street, Seattle, WA 98105-6246, United States.
College of Health Solutions, Arizona State University, 975 S Myrtle Ave., Tempe, AZ 85287, United States.
Neurosci Lett. 2024 Nov 20;843:138025. doi: 10.1016/j.neulet.2024.138025. Epub 2024 Oct 24.
Previous studies have revealed that auditory processing is modulated during the planning phase immediately prior to speech onset. To date, the functional relevance of this pre-speech auditory modulation (PSAM) remains unknown. Here, we investigated whether PSAM reflects neuronal processes that are associated with preparing auditory cortex for optimized feedback monitoring as reflected in online speech corrections. Combining electroencephalographic PSAM data from a previous data set with new acoustic measures of the same participants' speech, we asked whether individual speakers' extent of PSAM is correlated with the implementation of within-vowel articulatory adjustments during /b/-vowel-/d/ word productions. Online articulatory adjustments were quantified as the extent of change in inter-trial formant variability from vowel onset to vowel midpoint (a phenomenon known as centering). This approach allowed us to also consider inter-trial variability in formant production, and its possible relation to PSAM, at vowel onset and midpoint separately. Results showed that inter-trial formant variability was significantly smaller at vowel midpoint than at vowel onset. PSAM was not significantly correlated with this amount of change in variability as an index of within-vowel adjustments. Surprisingly, PSAM was negatively correlated with inter-trial formant variability not only in the middle but also at the very onset of the vowels. Thus, speakers with more PSAM produced formants that were already less variable at vowel onset. Findings suggest that PSAM may reflect processes that influence speech acoustics as early as vowel onset and, thus, that are directly involved in motor command preparation (feedforward control) rather than output monitoring (feedback control).
先前的研究表明，听觉处理在言语起始前的规划阶段会受到调制。迄今为止，这种言语起始前听觉调制（PSAM）的功能相关性仍不清楚。在这里，我们研究了 PSAM 是否反映了与准备听觉皮层进行优化的反馈监测相关的神经元过程，这种监测反映在在线言语纠正中。我们结合了先前数据集中的脑电图 PSAM 数据和同一参与者言语的新声学测量值，询问了个体说话者的 PSAM 程度是否与在 /b/-元音-/d/单词产生过程中元音内的发音调整的实施相关。在线发音调整被量化为从元音起始到元音中点的音渡变异性的变化程度（一种称为中心的现象）。这种方法还允许我们分别考虑音渡产生中的试验间变异性及其与 PSAM 的可能关系，以及在元音起始和中点处。结果表明，在元音中点处的音渡变异性明显小于在元音起始处。PSAM 与这种变异性的变化量没有显著相关，作为元音内调整的指标。令人惊讶的是，PSAM 不仅在元音的中间，而且在元音的起始处与音渡变异性呈负相关。因此，具有更多 PSAM 的说话者在元音起始时产生的音渡已经具有较小的变异性。研究结果表明，PSAM 可能反映了在元音起始时就会影响语音声学的过程，因此，它直接参与了运动指令的准备（前馈控制），而不是输出监测（反馈控制）。
