Speaking rate-induced acoustic variability in Parkinson’s disease

Abstract

The idea that speech consists of overlapping gestures that slide with respect to one another suggests that measurable kinematic, and hence, acoustic differences should characterize utterances produced with varying degrees of gesture overlap. [Saltzman and Munhall, Ecolog. Psych. 1, 333–382 (1989)]. Further research suggests that a simple acoustic model of overlapping gestures [Weismer et al., J. Phon. 23, 149–164 (1995)] accounts for some of the spectral and temporal variability in speech produced by individuals with apraxia of speech. One implication is that articulatory deficits associated with motor speech disorders can be modeled, in part, as disruptions in gesture overlap. The extent to which a model of overlapping gestures accounts for acoustic variability in other motor speech disorders is largely unknown. The present study explored the extent to which a simple acoustic model of overlapping gestures accounted for speaking-rate induced variability in F2 trajectories produced in target words by individuals with Parkinson’s disease (PD), young adults, and older adults. F2 onset frequency was used as an acoustic measure of overlapping consonantal and vocalic gestures; F2 onset frequency also was used to predict across-repetition temporal variability in F2 trajectories.