Voicing in severe apraxia of speech: perceptual and acoustic analysis of a single case

Abstract

This paper reports an acoustic and perceptual study of a patient with severe apraxia of speech (AOS), focusing on the ability to signal the contrast of voice versus voiceless on real and non-word stimuli. Unlike other acoustic studies in this area which have focused on voice onset time (VOT), acoustic measures extended to a bundle of features which signal the voicing contrast. These showed that the apraxic speaker retained the voicing contrast at a phonemic level, but could signal it only in word initial position through closure duration. The data also showed an absence of a lexical effect on real/non-word performance of the apraxic speaker, although a control speaker showed significant increase in response latency on non-word stimuli. The implications of this finding for a theory of impaired automatic speech encoding in AOS are discussed.