Assessing processing skills in speakers with parkinson's disease using delayed auditory feedback

This study assessed the processing abilities of speakers with Parkinson's disease (PD) who were rated as mildly to moderately impaired (using the Hoehn and Yahr Scale) by recording their responses to speech tasks under delayed auditory feedback (DAF). Ten speakers with PD, 10 matched normal geriatric speakers, and 10 young adults participated. Speakers were recorded under three DAF conditions (no DAF, delay of 125 ms, and delay of 231 ms) while they read, described pictures, or provided spontaneous speech samples. Speech rate, articulation rate, fluency, and intelligibility were measured. Introduction of DAF caused the three groups to perform in broadly similar fashions. DAF disrupted their speech by reducing their speech rate, articulation rate, and, to a lesser extent, their fluency. When reading the speakers with PD significantly decreased their speech and articulation rates compared to the controls. However, this did not translate into any benefits for the speakers with PD, as their fluency became somewhat worse and their intelligibility did not change. These results imply that the speakers with mild to moderate PD have problems with resource allocation in that they have reduced resources to monitor and produce speech concurrently. They also may be unable to divide their resources to overcome the interference induced by DAF.