An Autosegmental-Metrical Investigation of Intonation in People with Parkinson's Disease

Abstract

This study investigates the intonation in the read speech of two males with hypokinetic dysarthria resulting from idiopathic Parkinson's disease and compares them with two age-matched male controls. The investigation was carried out within the autosegmental-metrical framework (AM), which analyzes intonational contours as a sequence of abstract, discrete pitch targets (high or low tones) and permits analysis on two levels: the intonational phonology and its phonetic realisation. Despite its potential for revealing patterns of disordered usage, the AM approach has seldom been deployed in the analysis of disordered speech, and has never been used to investigate the intonation patterns of people with Parkinson's disease.Results showed that there were no differences between the participants with parkinsonian dysarthria and the healthy controls in the inventory of pitch accents and boundary tones (i.e., the phonological elements of intonation). Both groups used the same range of pitch accent types and boundary tones. However, there were differences in the phonetic realization of them. In particular, the speakers with parkinsonian dysarthria on average produced shorter intermediate and intonational phrases, used fewer pitch accents per intonational phrase, and had a narrower pitch range. Furthermore, their boundary tones did not always coincide with syntactic boundaries.The finding of preserved categorical elements of intonation suggests that the abstract representations of intonation are unaffected in these participants with parkinsonian dysarthria. However, the findings of problems with the distribution and phonetic realization suggests that there may be a disruption in the instantiation of those abstract representations either at the initial planning level or at the level of phonetic implementation.