Precision of fricative production in aphasia and apraxia of speech: A perceptual and acoustic study

Abstract

We examined the precision of fricative place of articulation production in speakers with aphasia and apraxia of speech. Articulatory precision was defined based on acoustic consistency across repeated productions of the same target words and on the acoustic distinction between similar fricative targets. Ten aphasic speakers with apraxia of speech, ten aphasic speakers without apraxia of speech, and ten normal control speakers produced words beginning with voiceless alveolar and palatal fricatives. The Bark transformed first spectral moment was computed in the middle of the fricative. For normal speakers, this measure varied little across repetitions and the target fricatives were clearly distinguished. For aphasic speakers with apraxia of speech, there was substantial spectral variability and overlap between targets. A similar pattern was found for aphasic speakers without apraxia of speech, although the effects were smaller in magnitude. Among these aphasic speakers, the greatest degree of spectral overlap was seen in speakers with low single-word intelligibility scores. The observed spectral imprecision is consistent with impaired phoneticmotor control, not only in the temporal, but also in the spatial domain of speech production.