Acoustic characteristics of Parkinsonian speech: a potential biomarker of early disease progression and treatment

Abstract

One of the frequent signs of Parkinson's disease (PD) is the presence of a progressive hypokinetic dysarthria. Numerous studies have since documented speech motor impairment, but attempts at quantifying any such changes longitudinally throughout the early course of the disease have been rare. In this study, a retrospective analysis of speech was conducted on two well-known individuals with PD and two matched controls to determine if certain acoustic measures were sensitive markers of early pathophysiologic changes or treatment response in PD. Acoustic analyses were conducted on samples of speech produced over a 10-year period surrounding the time of disease diagnosis. Analyses revealed that, for both PD cases, a decrease in fundamental frequency ( F 0) variability during free speech was detected prior to clinical diagnosis. Changes in F 0 variability and voice onset time (VOT) were also detected upon the initiation of symptomatic treatment. In a second experiment, an acoustical analysis of speech production was conducted on four newly diagnosed persons with PD and four matched controls, using a standard speech examination protocol. The objective of this follow-up study was to provide corroborating evidence for the results of the first experiment. Analyses revealed that F 0 variability during picture description was diminished in the participants with PD relative to their matched controls. In addition, pause duration was greater in participants with PD; no changes in VOT were detected. These observations suggest that early changes in speech are prodromal signs detectable using certain acoustic measures. A decrease in F 0 variability appears to be particularly sensitive to the early progression of the disease and to the initiation of pharmacologic intervention.