Tongue function in nondysarthric speakers with Parkinson's disease: An electromagnetic articulography investigation

Articulatory imprecision in Parkinson's disease (PD) has been attributed to reduced range of movement, rigidity, and abnormal speed of movement of the articulatory structures. Previous studies provided acoustic and kinematic evidence of lip muscle rigidity, reduced amplitude, and velocity of lip and jaw movement, mainly based on nonspeech measures. Very limited studies have documented the effects of PD on lingual kinematics during speech production. The present study aimed to investigate lingual kinematics during sentence production in a group of 7 nondysarthric speakers with PD using the electromagnetic articulograph (AG-200 EMA). Tongue-tip and tongue-back movements were recorded by the EMA system during sentence production. Seven non-neurologically impaired participants matched for age and sex served as a control group. Results revealed no significant difference on the distance of tongue movement. However, the PD group did show significantly reduced maximum velocity, maximum acceleration, maximum deceleration, and significantly longer duration of tongue movement. Rates of sentence production were also slower for the PD group. The subclinical differences in tongue kinematics of the nondysarthric speakers with PD documented in this study support that limitations in the range of tongue movement leading to articulatory undershoot may be a major contributor to articulatory impairment in dysarthric speakers with PD.