Acoustic Analysis of Internally versus Externally Guided Speech in Parkinson's Disease

Abstract

It is well established that individuals with Parkinson's disease (PD) exhibit differences in their ability to perform internally guided (IG) movements versus externally guided (EG) movements. The goal of this study was to evaluate the vocal parameters of utterances produced by ten speakers with Parkinson’s disease in two contexts: covert conversation (an IG context) and sentence reading (an EG context). Analyses were centered on measures of dysfluency, speaking rate and pitch variation. Results revealed significant differences for two of the ten speakers between speaking conditions. Namely, these speakers spoke faster and more fluently in the EG condition. Findings partially align with those of the original study (Weir-Mayta, 2014) which found perceptually salient differences between IG and EG conditions for six of the ten speakers. Future research is needed to continue to explicate the effects of external cuing on motor speech performance in individuals with PD.