The Speech Movement Disorder and its Rehabilitation in Parkinson’s Disease Using Augmented Visual Feedback


This dissertation comprises three studies that address the goals of better understanding the effects of Parkinson’s disease (PD) on speech movements and the development of a novel rehabilitation approach using augmented visual feedback (AVF) for individuals with an articulatory disorder due to PD. The first study examined jaw and tongue movements during sentence production in PD with respect to speech intelligibility and across different speaking styles, which are often used as intervention approaches (e.g., loud, clear speech). The results revealed consistently smaller jaw movements in individuals with PD relative to a control group. The results further showed that smaller tongue movement size was associated with lower ratings of speech intelligibility. The verbal cues to increase loudness, improve clarity, and reduce speaking rate generally resulted in changes in movement size and speed for both speakers with PD and healthy controls but the extent of change was smaller for the patient as compared to the control group. Using Cochrane-based methods, the second study systematically reviewed the PD literature that pertained to the use of AVF in motor rehabilitation. The findings showed that AVF is an effective tool for motor rehabilitation in PD. Treatment success can be further enhanced by providing large amounts and a high intensity of treatment, gamifying feedback, and providing knowledge of performance feedback in real-time and on 100% of practice trials. Taken together, the results of the first two studies guided the development of a novel therapy aimed at increasing tongue movement size using AVF, which provided visual feedback regarding movement performance, in addition to verbal cues. The final study investigated the effects of this novel therapy on tongue movement size and speech intelligibility in five patients with PD. The results indicated that AVF (+ verbal cue) may be beneficial in training participants to use large speech movements, compared to a verbal cue alone. The treatment effect on intelligibility was, however, not beneficial in 4/5 patients. The optimal extent of articulatory expansion needed to elicit benefits in speech intelligibility requires further investigation. Overall, this body of work furthered our understanding of the speech movement disorder in PD, and laid the groundwork for expanding evidence-based treatment options for this population in the future.