Dopaminergic medication effect on speech in Parkinson's disease: a kinematic study

Abstract

OBJECTIVE: To investigate the effect of levodopa on articulatory movement during Cantonese plosive production in individuals with Parkinson’s disease (PD) by comparing kinematic parameters before and after medication. BACKGROUND: Levodopa-based dopaminergic medication for PD was proven effective in treating movement problems. However, the literature sees contradictory findings regarding it effects on PD speech problems. As over 80% of patients with PD suffer from hypokinetic dysarthria with slurred speech and distorted consonant productions, management for PD speech is as important as other motor functioning. Previous perceptual and acoustic studies of PD speech mostly involved heterogeneous population and speech tasks which complicated data interpretation. The lack of kinematic data also limited our understanding of articulation errors and medication effects. Electromagnetic articulography (EMA) enabled the examination of articulatory patterns and the kinematic data provided important information about levodopa effect on early PD speech in the present study. METHODS: Five PD participants with mean age 62.4 ± 9.6 years were recruited in the study. Inclusion criteria included comparable type of prescription, dosage of medication, onset year of PD, HY stage and UPDRS scores. Speech stimuli used included disyllabic words, sentences and Chinese passage. The EMA system (AG500) was used for data collection. Three sensor coils were attached on upper lip (UL), lower lip (LL) and jaw (J), with four reference coils for calibrating of the movements of articulators. To establish “off-state”, Core Assessment Program for Intracerebral Transplantation (CAPIT) protocol was followed as PD participants took no PD medications for 12 hours before the experiment. Subsequently, recording for “on-state” was done after 1.5 hour of medication intake. RESULTS: Preliminary kinematic results were comparable across the 5 participants with regard to the medication effect. Movements of UL, LL and J were found different before and after medication. All articulators displayed more timely and coordinated movements with reduced peak velocity, increased time-to-peak-velocity and increased range of movement.