Phonological markers of sentence stress in ataxic dysarthria and their relationship to perceptual cues

A wide range of literature is available on the features of ataxic dysarthria, investigating segmental and prosodic characteristics by acoustic and perceptual means. However, very few studies have been published that look closely at the relationship between the observed phonetic disturbances and their perceptual sequelae, particularly in the area of prosody. The aim of the current study was therefore to examine the stress production of eight individuals with ataxic dysarthria and matched healthy controls, and to relate the results of phonological and perceptual evaluations to phonetic performances to better understand the relationship between these three components for speech outcomes.

Speakers performed a sentence stress task which was analysed phonologically in terms of inventory, distribution, implementation and function of pitch accentuation. These data were then evaluated in relation to previously published phonetic and perceptual results on the same speaker group by the authors. Results indicated that the speakers with ataxia used a wide range of pitch patterns, but pitch-accented a higher number of words, and produced shorter phrases. The increased number of pitch accents per phrase was furthermore reflected in a reduced percentage of de-accented words in post-focal position. Perceptual results established this pattern as the main cause for listener errors in identifying the intended stressed item in an utterance. In addition, the performances of two speakers are discussed in greater detail. Although they were unable to de-accent, they nevertheless marked stress appropriately through phonetic compensatory strategies.