Effect of Speech Task on Intelligibility in Dysarthria: A Case Study of Parkinson’s Disease

This study assessed intelligibility in a dysarthric patient with Parkinson’s disease (PD) across five speech production tasks: spontaneous speech, repetition, reading, repeated singing, and spontaneous singing, using the same phrases for all but spontaneous singing. The results show that this speaker was significantly less intelligible when speaking spontaneously than in the other tasks. Acoustic analysis suggested that relative intensity and word duration were not independently linked to intelligibility, but dysfluencies (from perceptual analysis) and articulatory/resonance patterns (from acoustic records) were related to intelligibility in predict-able ways. These data indicate that speech production task may be an important variable to consider during the evaluation of dysarthria. As speech production efficiency was found to vary with task in a patient with Parkinson’s disease, these results can be related to recent models of basal ganglia function in motor performance. ª 2002 Elsevier Science (USA) Key Words: intelligibility; dysarthria; Parkinson’s; speech; reading; repetition; singing. Parkinson’s disease (PD) is caused by basal ganglia dysfunction and creates a movement disorder characterized by bradykinesia (slow movements), muscle rigidity, and resting tremor. Parkinson’s disease often produces hypokinetic dysarthria, typi-fied by imprecise articulation, prosodic abnormalities, disturbance of speech rate, an