Intonation and speech rate in Parkinson's disease: general and dynamic aspects and responsiveness to levodopa admission

Objective: The aim of our study was the analysis of fundamental frequency (F(0)) variability (fundamental frequency standard deviation [F(0)SD]) and net speech rate (NSR) in the course of reading in Parkinsonian patients' speech, with special emphasis on the changes of F(0)SD and NSR from the first to the last sentence of the task.

Patients and methods: We examined 138 patients with Parkinson's disease (PD) and 50 age-matched control persons using a standardized reading task with subsequent acoustical analysis of F(0)SD and NSR. A subgroup of 20 PD patients underwent a standardized levodopa challenge.

Results: F(0)SD in PD patients was significantly reduced compared with the control group when based on the measurement of the entire reading task. Furthermore, in the PD group, NSR and F(0)SD showed significant changes from the first to the last sentence of the reading task, but no correlation was seen between NSR and F(0)SD. Standardized levodopa administration had no effect on NSR and F(0)SD when related to the entire reading passage, but the aforementioned decline of F(0) variability in the course of reading seemed to be counterbalanced by levodopa administration.

Conclusions: In this large series of PD patients, previous findings of reduced F(0)SD in PD were confirmed. Additionally, this is the first analysis to show an increasing reduction of F(0) variability in the course of reading mirroring abnormalities in the dynamical aspects of speech in PD. According to the results of the levodopa challenge, dopaminergic stimulation seems to ameliorate dynamic intonation changes over time, whereas overall intonation variability might be a PD symptom independent of dopaminergic control.