Rate reduction methods for improving speech intelligibility of dysarthric speakers with Parkinson's disease

Three speakers with moderate idiopathic Parkinson's disease participated in a speech therapy program aimed at improving speech intelligibility by reducing speech rate. All speakers had a dysarthria characterized by a fast speaking rate, poor articulation, and some dysfluency. While treatment protocols varied somewhat for each, the general protocol involved three steps: delayed auditory feedback (DAF), DAF plus traditional, clinician-directed therapy, and DAF plus a clinician-directed prolonged speech therapy. A single-subject multiple baseline design was used to determine if rate reduction improved intelligibility during reading, picture description, and spontaneous speech tasks. Continued exposure to DAF did not appear to cause reductions in speaking rate. Combining DAF and prolonged speech caused the speakers to respond differently. Speaker 1 reduced his rate and improved his intelligibility scores. These high intelligibility scores were maintained when speaking rate was gradually increased. Speaker 2's rate and intelligibility scores were erratic regardless of the therapy protocol employed. Speaker 3, although not responding to the treatment protocols, showed an increase in his posttherapy intelligibility scores compared to his pretherapy scores. The results are discussed in terms of possible cognitive deficits in speakers with Parkinson's disease which result in poor monitoring skills and attentional deficits. Also discussed is the viability of different types of therapy protocols for speakers with Parkinson's disease.