Abstract
Background: Dysprosody is a common feature in speakers with hypokinetic dysarthria. However, speech prosody varies across different types of speech materials. This raises the question of what is the most appropriate speech material for the evaluation of dysprosody.
Aims: To characterize the prosodic impairment in Cantonese speakers with hypokinetic dysarthria associated with Parkinson's disease, and to determine the effect of different types of speech stimuli on the perceptual rating of prosody.
Methods & Procedures: Speech data in the form of sentence reading, passage reading, and monologue were collected from ten Cantonese speakers with Parkinson's disease. Perceptual analysis was conducted on ten prosodic parameters to evaluate five dimensions of prosody, based on a theoretical framework: pitch, loudness, duration, voice quality, and degree of reduction.
Outcomes & Results: The results showed that the most severely affected prosodic parameters were monopitch, harsh voice, and monoloudness, followed by breathy voice and prolonged interval. Differences were noted between speakers with mild and moderate dysprosody. No statistically significant differences were found between the three types of stimuli. However, qualitative analysis revealed noticeable differences between the three stimuli in two speakers.
Conclusions & Implications: The prosodic profile of Cantonese speakers with hypokinetic dysarthria is similar to those of other languages (for example, English). The involvement of two new dimensions in the definition of prosody (voice quality and degree of reduction) provides additional insight in differentiating patients with mild and moderate dysarthria. Further investigation on the use of speech materials in the clinical evaluation of speech prosody in speakers with dysarthria is needed, as no single task was found to represent a patient's performance under all circumstances.
Acknowledgements
The authors gratefully acknowledge all the speakers and listeners for their participation in the present study. They thank Mrs Lorinda Kwan and the Hong Kong Parkinson's Disease Foundation (particularly Dr Tsoi Tak Hong and Professor S. L. Ho) for their assistance with subject referral. The authors are also grateful to Ms Susanne So for her help in data collection. This study was based on an undergraduate dissertation conducted by the third author, under the supervision of the first and second authors.