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.
Temporal control has often been suspected to be a critical factor in intonation production. In particular, disturbance in the production of fundamental frequency (F0) associated with intonation in patients with aphasia has been attributed to a primary underlying deficit in speech timing. The present study examined the speech timing abilities of two groups of patients with fluent and nonfluent aphasia who were found in a companion study to have relatively normal intonation production ability. Results indicated severe temporal control abnormalities for the patients with nonfluent aphasia. The fluent aphasic patients performed at comparable levels with the normal subjects, although in absolute terms their durations were also generally longer than normal. These findings do not support the view that intonation production depends critically on speech timing, and that its disturbance in aphasia is due to underlying temporal control deficit.
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