Department of Speech-Language-Hearing: Sciences & Disorders, University of Kansas, Lawrence.
J Speech Lang Hear Res. 2019 Sep 20;62(9):3248-3264. doi: 10.1044/2019_JSLHR-S-19-0058. Epub 2019 Aug 21.
Purpose The aim of this study was to determine the relation of tongue-jaw coupling to phonetic distinctiveness of vowels in persons at different stages (i.e., early, middle, late) of bulbar motor involvement in amyotrophic lateral sclerosis (ALS) and healthy controls. Method The pattern of spatial tongue-jaw coupling was derived from 11 individuals with ALS and 11 healthy controls using the parallel factor analysis. Two articulatory components, which correspond to tongue displacement independent of the jaw (iTongue) and jaw contribution to tongue displacement (cJaw), were extracted from the composite tongue-jaw displacement. These articulatory components were correlated with F1 (i.e., height) and F2-F1 (i.e., advancement) of 4 vowels (/i/, /u/, /æ/, and /ɔ/) across all participants in each group. In addition, a comprehensive index of functional tongue-jaw coupling was derived as the ratio of cJaw/(iTongue + cJaw), and an acoustic index of vowel distortion (VowelDis) was derived to quantify the overall disease-related changes in phonetic distinctiveness of vowels. Based on these indices, disease-related changes in tongue-jaw coupling and phonetic distinctiveness of vowels were examined in individuals at the early, middle, and late stages of the disease. Results For healthy controls, both iTongue and cJaw contributed to F2-F1, while only cJaw contributed to F1. For individuals with ALS, both iTongue and cJaw contributed to F1, whereas only cJaw contributed to F2-F1. Disease-related changes in tongue-jaw coupling included (a) an overall decrease of the percent contribution of the tongue to the composite tongue-jaw displacement accompanied by an increase of percent contribution of the jaw and (b) several changes in the direction of tongue and jaw displacements occurred at different stages of the disease. These disease-related changes in tongue-jaw coupling had various impacts on phonetic distinctiveness of vowels, resulting in (a) a backward shift of front vowels and reduced front-back vowel contrasts, which occurred early and throughout the disease stages; (b) raising of all vowels during the middle stage of the disease; and (c) reduced high-low vowel contrasts during the late stage of the disease. Overall, phonetic distinctiveness of vowels deteriorated progressively throughout the disease course. Conclusions Different from healthy controls who established optimal functional coupling between the tongue and the jaw during vowel productions, individuals at the early-to-middle stages of bulbar ALS showed various adaptive changes in tongue-jaw coupling in response to the disease-related biomechanical and muscular changes in the articulators (particularly in the tongue). These adaptive changes in tongue-jaw coupling were found to be partially effective in mitigating the negative effect of articulatory involvement on phonetic distinctiveness of vowels. As the disease progressed to the late stage, such adaptations appeared to be no longer evident, resulting in a substantial overall reduction of vowel contrasts.
本研究旨在确定舌颌耦合与肌萎缩侧索硬化（ALS）患者不同阶段（早期、中期、晚期）球部运动受累者和健康对照者元音语音清晰度的关系。
采用平行因子分析，从 11 名 ALS 患者和 11 名健康对照者中得出空间舌颌耦合模式。从复合舌颌位移中提取出两个发音组件，即独立于颌部的舌位移（iTongue）和颌部对舌位移的贡献（cJaw）。将这些发音组件与每组所有参与者的 4 个元音（/i/、/u/、/æ/和/ɔ/）的 F1（即高度）和 F2-F1（即前伸）进行相关分析。此外，还得出了功能舌颌耦合的综合指数，即 cJaw/（iTongue+cJaw），并得出了元音失真的声学指数（VowelDis），以量化元音语音清晰度的整体疾病相关性变化。基于这些指标，检查了疾病早期、中期和晚期个体的舌颌耦合和元音语音清晰度的疾病相关性变化。
对于健康对照者，iTongue 和 cJaw 均有助于 F2-F1，而仅 cJaw 有助于 F1。对于 ALS 患者，iTongue 和 cJaw 均有助于 F1，而仅 cJaw 有助于 F2-F1。舌颌耦合的疾病相关变化包括：（a）舌对复合舌颌位移的贡献总体减少，而颌的贡献增加；（b）疾病不同阶段舌和颌位移的方向发生了一些变化。这些舌颌耦合的疾病相关变化对元音的语音清晰度有不同的影响，导致：（a）前元音向后移动，前后元音对比减小，这种情况发生在疾病早期并贯穿整个疾病阶段；（b）疾病中期所有元音升高；（c）疾病晚期高元音和低元音对比减小。总的来说，元音的语音清晰度在疾病过程中逐渐恶化。
与在发元音时舌颌之间建立了最佳功能耦合的健康对照者不同，球部 ALS 的早期到中期患者的舌颌耦合出现了各种适应性变化，以应对发音器官（特别是舌部）的与疾病相关的生物力学和肌肉变化。这些舌颌耦合的适应性变化在一定程度上有助于减轻发音器官受累对元音语音清晰度的负面影响。随着疾病进入晚期阶段，这些适应似乎不再明显，导致元音对比的总体大幅减少。
