Effects of Increased Loudness on Tongue Movements during Speech in Nondysarthric Speakers with Parkinson's Disease

This study aimes to examine the effets of loud speech on tongue movements in people with Parkinson's disease (PD). The kinematics and speech moter stability of the tongue tip during the habitual and loud speech produced by eight nondysarthric participants with PD and eight age- and gender-matched non-neurologically imparted speakers were investigated using electromagnetic articulography. Sentences loaded with alveolar consonants were recorded in habitual and experimental-cued loudness conditions. Kinematic parameters (velocity, acceleration, deceleration, duration, and distance) were analyzed from word-initial/t/productions within repetitions of one sentence, while the spatiotemporal index, analyzed across repetitions of a second sentence, proved a quantitative measurement of the spatial and temporal stability of tongue tip movement. During habitual speech, there was no differences in kinematic parameters between groups. During loud speech, whereas particupants with PD increased maximum veloctiy, the control speakers increased the majority of kinematic parameters excluding durating and approach phase acceleration. The speech motor stability of the tongue tip was similar across groups during both speech conditions and was not affected by increased loudness. Clinical treatment implications are positive because loud speech can increase tongue tip movements without shifting speech moter stability despite the increased demand on the motor system.