Speech timing in apraxia of speech versus conduction aphasia

This study examined temporal parameters of speech in subjects with apraxia of speech, conduction aphasia, and normal speech. They were asked to repeat target words in a carrier phrase 10 times. Acoustic analyses involved measurement of stop gap duration, voice onset time, vowel nucleus duration, and consonant-vowel (CV) duration. Speakers with apraxia of speech had longer and more variable stop gap, vowel, and CV durations than did subjects with aphasia or normal speech. Speakers with conduction aphasia had longer vowel durations and CV durations than subjects with normal speech. Also, subjects with apraxia of speech showed greater token-to-token variability than the other subject groups. The variability shown by subjects with apraxia of speech was significantly correlated with perceptual judgments of their speech. The significance of these results is discussed in the context of motoric and phonological explanations for apraxia of speech and conduction aphasia.