Effect of intensive voice treatment on tone-language speakers with Parkinson's disease

The aim of this study was to investigate the effect of intensive voice therapy on Cantonese speakers with Parkinson's disease. The effect of the treatment on lexical tone was of particular interest. Four Cantonese speakers with idiopathic Parkinson's disease received treatment based on the principles of Lee Silverman Voice Treatment (LSVT). Outcome measures included perceptual measures and acoustic correlates of loudness, pitch, intonation, and tone (only intonation and tone are detailed in this study). All four participants demonstrated an increase in loudness, an increase in pitch and pitch range, and improved intonation during connected speech, as measured perceptually and acoustically. However, there were no obvious changes in the accuracy of lexical tone production, based on either phonetic transcription or acoustic analysis. The lack of improvement in lexical tones may support previous claims of a dissociation in fundamental frequency control for intonation and lexical tone production.