Phonetic basis of phonemic paraphasias in aphasia: Evidence for cascading activation.
Phonemic paraphasias are a common presenting symptom in aphasia and are thought to reflect a deficit in which selecting an incorrect phonemic segment results in the clear-cut substitution of one phonemic segment for another. The current study re-examines the basis of these paraphasias. Seven left hemisphere-damaged aphasics with a range of left hemisphere lesions and clinical diagnoses including Broca's, Conduction, and Wernicke's aphasia, were asked to produce syllable-initial voiced and voiceless fricative consonants, [z] and [s], in CV syllables followed by one of five vowels [i e a o u] in isolation and in a carrier phrase. Acoustic analyses were conducted focusing on two acoustic parameters signaling voicing in fricative consonants: duration and amplitude properties of the fricative noise. Results show that for all participants, regardless of clinical diagnosis or lesion site, phonemic paraphasias leave an acoustic trace of the original target in the error production. These findings challenge the view that phonemic paraphasias arise from a mis-selection of phonemic units followed by its correct implementation, as traditionally proposed. Rather, they appear to derive from a common mechanism with speech errors reflecting the co-activation of a target and competitor resulting in speech output that has some phonetic properties of both segments.
['Kurowski|Kathleen|K|', 'Blumstein|Sheila E|SE|']
D000368:Aged D000369:Aged, 80 and over D001039:Aphasia, Broca D001041:Aphasia, Wernicke D005260:Female D006801:Humans D008297:Male D008875:Middle Aged D010700:Phonetics D013060:Speech D013068:Speech Production Measurement
Phonemic paraphasias Aphasia Cascading activation Acoustic trace