Acoustic correlates of laryngeal control: Parkinson's and healthy older adults

Vocal fold tension is commonly used to control pulmonary airflow and subglottal pressure, resulting in a positive f0-intensity correlation. Since Parkinson's disease (PD) constrains fine movements, this mechanism may be impaired in PD. We analyzed the f0-intensity correlation in PD and a healthy age- and gender-matched control group. For that, we extracted gender-normalized f0, intensity, and spectral emphasis (SE) from each syllable in three sentences of a read text. Additionally, from a sustained [a] task, we measured maximum phonation time ([a] duration; MPT) as well as jitter and shimmer (combined using PCA; JS). Using Linear Mixed Models, we confirmed the f0-intensity correlation in each group. Furthermore, JS interacted with intensity, indicating that voice instability weakens the correlation. No MPT effect was found. Importantly, even controlling for JS and MPT, the f0-intensity correlation was significantly weaker in PD. Lastly, we build a model using SE instead of intensity and only a negative correlation was found. Overall, this study suggests that voice instability negatively affects airflow control, but is not sufficient to explain its reduction in PD. Moreover, it indicates that the SE-f0 relationship is preserved in PD and it is not affected by the voice parameters analyzed.