Department of Communication Sciences and Disorders, University of Wisconsin-Madison.
Department of Psychology, University of California, Berkeley.
J Speech Lang Hear Res. 2021 Jun 18;64(6S):2234-2247. doi: 10.1044/2021_JSLHR-20-00270. Epub 2021 Apr 26.
Purpose Individuals with cerebellar ataxia (CA) caused by cerebellar degeneration exhibit larger reactive compensatory responses to unexpected auditory feedback perturbations than neurobiologically typical speakers, suggesting they may rely more on feedback control during speech. We test this hypothesis by examining variability in unaltered speech. Previous studies of typical speakers have demonstrated a reduction in formant variability (centering) observed during the initial phase of vowel production from vowel onset to vowel midpoint. Centering is hypothesized to reflect feedback-based corrections for self-produced variability and thus may provide a behavioral assay of feedback control in unperturbed speech in the same manner as the compensatory response does for feedback perturbations. Method To comprehensively compare centering in individuals with CA and controls, we examine centering in two vowels (/i/ and /ɛ/) under two contexts (isolated words and connected speech). As a control, we examine speech produced both with and without noise to mask auditory feedback. Results Individuals with CA do not show increased centering compared to age-matched controls, regardless of vowel, context, or masking. Contrary to previous results in neurobiologically typical speakers, centering was not affected by the presence of masking noise in either group. Conclusions The similar magnitude of centering seen with and without masking noise questions whether centering is driven by auditory feedback. However, if centering is at least partially driven by auditory/somatosensory feedback, these results indicate that the larger compensatory response to altered auditory feedback observed in individuals with CA may not reflect typical motor control processes during normal, unaltered speech production.
由于小脑变性而导致小脑性共济失调（CA）的个体对外界听觉反馈干扰表现出更大的反应性补偿反应，这表明他们在言语过程中可能更依赖反馈控制。我们通过检查未经改变的言语中的变异性来检验这一假设。先前对典型说话者的研究表明，在元音起始到元音中点的初始阶段，观察到的共振峰变异性（中心化）减少。中心化被假设为反映了对自身产生的变异性的基于反馈的修正，因此可以像补偿反应对反馈干扰一样，为未受干扰的言语中的反馈控制提供行为测定。方法：为了全面比较 CA 患者和对照组中的中心化，我们在两种语境（孤立词和连续语音）下检查两个元音（/i/和/ɛ/）中的中心化。作为对照，我们检查了有噪声和无噪声的语音，以掩盖听觉反馈。结果：无论在元音、语境或掩蔽的情况下，CA 患者的中心化都没有比年龄匹配的对照组增加。与先前在神经生物学典型说话者中的结果相反，两组的中心化都不受掩蔽噪声的影响。结论：在有和没有掩蔽噪声的情况下中心化的相似幅度质疑中心化是否是由听觉反馈驱动的。然而，如果中心化至少部分由听觉/躯体感觉反馈驱动，那么这些结果表明，在 CA 患者中观察到的对外界听觉反馈的更大补偿反应可能并不反映正常、未改变的言语产生过程中的典型运动控制过程。
