The effect of levodopa on speech in Parkinson's disease: Musical' scale study

Abstract

This paper aims to examine the effect of levodopa on speech in patients with Parkinson's disease. Our hypothesis is that, in such a task, speech production should be phonetically affected for parkinsonian patients and improved by L-Dopa treatment. In order to determine dopamine effect, oral productions of 14 parkinsonian patients of the akinetic type have been collected, in the OFF and ON states. They have then been compared to those of control subjects. The specific aim of this study is (a) to examine the ability of patients to handle the variations in fundamental frequency of their voice as well as to master the rise in frequency required by the task, i.e. production of the musical scale (b) to measure the palliative effects that can be induced treatment based on L-Dopa. Effects relating to the L-dopa administration diverge according to the patients, the year post diagnosis and the Parkinson's disease severity degrees. Compared to our control population, our parkinsonian subjects present prosodic disorders, in particular on the level of the fundamental frequency management. This dysfunction would come from the akinesy, the breathing deficit and the problems of vocal cords vibration. These results confirm in part Darley hypothesis, knowing that the parkinsonian “dysprosody” would come from a peripheral neuro-engine dysfunction affecting the larynx motor activity.