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

This study aims to examine the effects of loud speech on tongue movements in people with Parkinson'? disease (PD). The kinematics and speech motor stability of the tongue tip during habitual and loud speech produced by eight nondysarthric participants with PD and eight age- and gender-matched non-neurologieally impaired speakers were investigated using electromagnetic articulography. Sentences loaded with alveolar consonants were recorded in habitual and experimenter-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 spatiotem-poral index, analyzed across repetitions of a second sentence, provided a quantitative measurement of the spatial and temporal stability of tongue tip movement. During habitual speech, there were no differences in kinematic parameters between groups. During loud speech, whereas participants with PD increased maximum velocity, the control speakers increased the majority of kinematic parameters excluding duration 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 motor stability despite the increased demand on the motor system. INTRODUCTION