Phonological and phonetic impairment in aphasic speech: an acoustic study of the voice onset time of six French-speaking aphasic patients.

The aim of the present study is to contribute to the description of the speech production deficits in French-speaking aphasic patients, so as to shed light on their potential phonetic and/or phonological disorders. Acoustic studies of aphasics' speech productions remain relatively infrequent, especially in French, and when entering into the specifics, often lead to inconsistent results. We conducted a multiple-case study on six aphasic patients, four with non-fluent aphasia and two with fluent aphasia. They were administered a variety of language and neuropsychological tasks, then they participated in a customized non-word repetition task. Acoustic analyses of their speech productions were performed, focussing on VOT as the main acoustic correlate of the voicing contrast for oral stops. Other atypicalities in their productions were also classified. Results showed variable and mainly "mixed" phonetic-phonological impairment profiles that differed from the traditional hypotheses made in the literature about the speech deficits to be expected as a function of type of aphasia. Our results support the use of acoustic analyses in order to complete language examination in aphasic patients but also suggest that the frontier between phonological and phonetic impairment is not clear-cut. These outcomes are better accounted for by theories and models postulating close relationships between the phonological and phonetic levels of processing.