Acoustic and kinematic insights into articulatory sensorimotor control in Parkinson’s disease

Many people with Parkinson’s disease suffer from speech problems, but we do not quite know where these problems come from. In the current dissertation, we investigated two aspects of speech motor control in a group of individuals with Parkinson’s disease and typical speakers.

First, we assessed how well the tongue, the lips and the jaw function. We looked at our participants’ vowel space, which can serve as a good indicator of how intelligible someone’s speech is: overall, the smaller someone’s vowel space is, the less understandable their speech. We found no differences between typical speakers and individuals with Parkinson’s disease on group level. However, we did find that only male speakers with Parkinson’s disease had smaller vowel spaces than male typical speakers. This highlights the importance of including sex as a variable in analyses. We additionally assessed the presence of tremor in the tongue, the lips and the jaw. We found that the group of individuals with Parkinson’s were more likely to show this kind of tremor during only one movement task. This highlights the importance of including typical speakers, as they can show tremor as well. 

The second potential origin of speech impairment in Parkinson’s disease is sensory impairment in the way we process auditory information: whenever we speak, our brain is constantly checking whether we said the right thing. If there is a mistake, our brain will send a signal to fix this mistake. In our study, we tested this and found that both individuals with Parkinson’s disease and typical speakers can fix small errors detected during speaking. However, individuals with Parkinson’s disease were slower and less effective in fixing these errors.

Dissertation: https://hdl.handle.net/11370/78afa63a-7898-4f42-b95f-dfd5e032c780