Speech task affects quality of articulation in Parkinsonian dysarthria

To examine the effect of speech task on articulation, this study assessed speech in a dysarthric patient across four production tasks: spontaneous speech, repetition, reading, and repeated singing, using the same phrases for all tasks. The study design ensured that all phrases were heard in all production tasks, but no listener heard any phrase twice. Data were obtained from listeners’ identification and difficulty rating scores, perceptual judgments, and acoustic analyses. Items produced spontaneously were significantly less intelligible than the same phrases produced in the other three tasks (29% vs 79% correct identification). Spontaneous speech was also rated as more difficult to understand than other speech tasks. While relative intensity and word duration were not linked to intelligibility, dysfluencies and distorted articulatory/resonance patterns were found significantly more often in spontaneous than in the other tasks. These indications of variable speech production efficiency were found in a patient with Parkinson’s disease, which is associated with basal ganglia impairment. These results can be related to recent models of normal basal ganglia function, which emphasize motor planning and monitoring. One explanation for the different articulation patterns reported here may be the availability of an external ‘‘model’’ which aids planning in the reading and repetition tasks.