Are vowel errors influenced by consonantal context in the speech of persons with aphasia?

Abstract

The literature suggests that vowels and consonants may be affected differently in the speech of persons with conduction aphasia (CA) or nonfluent aphasia with apraxia of speech (AOS). Persons with CA have shown similar error rates across vowels and consonants, while those with AOS have shown more errors for consonants than vowels. These data have been interpreted to suggest that consonants have greater gestural complexity than vowels. However, recent research [M. Boyle et al., Proc. International Cong. Phon. Sci., 3265–3268 (2003)] does not support this interpretation: persons with AOS and CA both had a high proportion of vowel errors, and vowel errors almost always occurred in the context of consonantal errors. To examine the notion that vowels are inherently less complex than consonants and are differentially affected in different types of aphasia, vowel production in different consonantal contexts for speakers with AOS or CA was examined. The target utterances, produced in carrier phrases, were bVC and bV syllables, allowing us to examine whether vowel production is influenced by consonantal context. Listener judgments were obtained for each token, and error productions were grouped according to the intended utterance and error type. Acoustical measurements were made from spectrographic displays.