A preliminary study of factors influencing perception of articulatory rate in Parkinson disease.

This investigation was a preliminary study of factors influencing perception of articulatory rate in idiopathic Parkinson disease (PD). Nine men with mild to moderate idiopathic PD and 9 healthy men of a similar age read the Farm Passage at habitual, fast, and slow reading rates. Spontaneous speech samples also were obtained. Speech severity for participants with PD was mild to moderate; prominent perceptual characteristics further suggested hypokinetic dysarthria. Nine listeners estimated the articulatory rate of speech runs (i.e., stretch of speech bounded by pauses) extracted from the reading and spontaneous speech samples. Regression analysis was used to explore the relationship between articulatory rate (i.e., syllables produced per second excluding pauses) and perceptual impressions of articulatory rate as well as the relationship between fundamental frequency (F0) range and perceptual estimates of articulatory rate. Regression functions predicting perceptual estimates of articulatory rate from F0 range were not significant for either speaker group. The regression analyses relating articulatory rate and perceptual estimates of articulatory rate, however, revealed a significant, positive relationship between the two measures for both speaker groups. There also was a nonsignificant trend for perception of articulatory rate to grow more rapidly for Parkinsonian speech samples. Although the current findings should be interpreted with caution until they have been validated by additional studies using much larger speaker populations and more extensive speech samples, the results hint at the possibility that perceptual impressions of articulatory rate in PD may overestimate the actual, physical rate. The results also highlight the importance of speech-language pathologists complimenting perceptual judgements of articulatory rate with physical measures.