Coordination and timing of speech gestures in Parkinson’s disease

Many individuals with Parkinson's disease (PD) experience articulatory difficulties, which often have a considerable impact on their quality of life. It is currently poorly understood which mechanisms underlie these articulatory difficulties. In order to learn more about these mechanisms, this dissertation examined the coordination and timing of speech gestures in PD speech. Both these aspects are intrinsic to articulation, but at current it is unknown how they relate to the articulatory difficulties observed in PD speech. The studies in this dissertation address this issue using state-of-the-art methods. In the first study of this thesis, the effect of levodopa on vowel articulation in PD was examined. The results from this study suggest that articulation of vowels is not influenced by levodopa. In the following two studies, spatial and temporal aspects of speech gestures have been examined. The results from these studies suggest that the timing of speech gestures, and also the coupling between speech gestures is impaired in PD. In the final study of this dissertation, the prevalence and nature of tongue tremor in individuals with PD were investigated. Using a computer algorithm, we found different types of tongue tremor in our data, which we believe may affect the timing of speech gestures. Together, the studies in this dissertation show that coordination and timing are indeed impaired in the speech of (at least some) individuals with PD. We believe that this impairment may be caused by the presence of malfunctioning regulatory mechanisms in PD speech

Accuracy assessment of two electromagnetic articulographs:NDI Wave and NDI Vox

Purpose This study compares two electromagnetic articulographs manufactured by Northern Digital, Inc.: the NDI Wave System (from 2008) and the NDI Vox-EMA System (from 2020). Method Four experiments were completed: (a) comparison of statically positioned sensors, (b) tracking dynamic movements of sensors manipulated using a motor-driven LEGO apparatus, (c) tracking small and large movements of sensors mounted in a rigid bar manipulated by hand, and (d) tracking movements of sensors rotated on a circular disc. We assessed spatial variability for statically positioned sensors, variability in the transduced Euclidean distances between sensor pairs, and missing data rates. For sensors tracking circular movements, we compared the fit between fitted ideal circles and actual trajectories. Results The average sensor pair tracking error (i.e., the standard deviation of the Euclidean distances) was 1.37 mm for the WAVE and 0.12 mm for the VOX during automated trials at the fastest speed, and 0.35 mm for the WAVE and 0.14 mm for the VOX during the tracking of large manual movements. The average standard deviation of the fitted circle radii charted by manual circular disc movements was 0.72 mm for the WAVE sensors and 0.14 mm for the VOX sensors. There was no significant difference between the WAVE and the VOX in the number of missing frames. Conclusions In general, the VOX system significantly outperformed the WAVE on measures of both static precision and dynamic accuracy (automated and manual). For both systems, positional precision and spatial variability were influenced by the sensors' position relative to the field generator unit (worse when further away)

A review of data collection practices using electromagnetic articulography

This paper reviews data collection practices in electromagnetic articulography (EMA) studies, with a focus on sensor placement. It consists of three parts: in the first part, we introduce electromagnetic articulography as a method. In the second part, we focus on existing data collection practices. Our overview is based on a literature review of 905 publications from a large variety of journals and conferences, identified through a systematic keyword search in Google Scholar. The review shows that experimental designs vary greatly, which in turn may limit researchers' ability to compare results across studies. In the third part of this paper we describe an EMA data collection procedure which includes an articulatory-driven strategy for determining where to position sensors on the tongue without causing discomfort to the participant. We also evaluate three approaches for preparing (NDI Wave) EMA sensors reported in the literature with respect to the duration the sensors remain attached to the tongue: 1) attaching out-of-the-box sensors, 2) attaching sensors coated in latex, and 3) attaching sensors coated in latex with an additional latex flap. Results indicate no clear general effect of sensor preparation type on adhesion duration. A subsequent exploratory analysis reveals that sensors with the additional flap tend to adhere for shorter times than the other two types, but that this pattern is inverted for the most posterior tongue sensor

The influence of alcohol on L1 vs. L2 pronunciation

In this study, we investigated the influence of alcohol intake on pronunciation in both a native and a non-native language. At a Dutch music festival, we recorded the speech of 87 participants in Dutch (native language) and English (non-native language) when reading a few sentences in both languages. The recorded audio samples were judged by 108 sober native Dutch speakers in a perception experiment at the same festival. Participants were asked to judge how clear the Dutch pronunciations of a random selection of speakers were and how native-like the English pronunciations were. The results, analysed using generalized additive modelling (which is able to identify non-linear relationships), indicated a small linear negative relationship between alcohol intake and clarity of Dutch speech. For English there was no effect of alcohol intake on the native-likeness of the English pronunciations