Articulatory Kinematics During Stop Closure in Speakers with Parkinson�s Disease

Purpose: The goal of this exploratory study was (a) to investigate the differences in articulatory movements during the closure phase of bilabial stop consonants with respect to distance, displacement, and timing of motion between individuals with Parkinson’s Disease (PD) and healthy controls; and (b) to investigate changes in articulatory movements of speakers with PD when they voluntarily vary the degree of speech intelligibility.Methods: Six participants, 4 PD and 2 healthy control (HC) speakers, participated in this study. The stimulus was a sentence containing several bilabial stop consonants (i.e., “Buy Bobby a puppy”). Movement data were collected using the Wave Speech Research System (NDI, Canada). Movement measures included duration, distance, and displacement and speed of the tongue front, tongue back, upper lip, lower lip, and jaw.Results: Speakers with PD and HC speakers produced observable articulatory differences during the stop closure of bilabial stops. Generally, the PD group produced smaller articulatory movement and had longer closure durations than the HC group. Regarding changes in speaking mode, the two groups made observable, but different articulatory changes during the stop closure. For more clear speech, both groups made greater articulatory movements and decreased the stop closure duration. For less clear speech, the HC group demonstrated reduced articulatory movements and longer closure durations whereas the PD group made greater articulatory movements and longer closure durations.Discussion: The findings of this study revealed several articulatory differences during the stop closure between the two speaking groups. For more clear speaking conditions, speakers in the PD group can successfully compensate for reduced articulatory movement by producing exaggerated lower lip and jaw movement. These findings support the use of more clear speaking modifications as a therapeutic technique to elicit better articulatory movement among speakers with PD. However, it also appears the PD group has difficulty producing fine motor articulatory changes (e.g., less clear speech).