Impaired speech perception in aphasic patients: event-related potential and neuropsychological assessment

The mismatch negativity component (MMN) of auditory event-related potential s (ERP) was recorded in four aphasic patients and in age, gender and educat ion matched controls. The MMN changes elicited by tone, vowel, voicing stop consonant and place-of articulation contrasts were recorded over both hemi spheres. The results of MMN amplitude, latency and distribution differences between aphasics, and controls were analyzed in detail. An extensive neuro psychological investigation was performed in order highlight the assumed di ssociation and possible interactions between the impaired acoustic/phonetic perception and deficient comprehension in aphasic patients. Our principal finding was that MMN elicited by pitch deviations is not enough sensitive t o distinguish between patients and age-matched controls. The MMN elicited b y consonant contrasts was found to be the most vulnerable in aphasic patien ts investigated. The MMN elicited by voicing ([ba:] vs. [pa:]) and place-of -articulation ([ba:] vs. [ga:]) could be characterized by total lack, disto rted or very limited distribution and correlated with the patients' perform ance shown in the behavioral phoneme discrimination task. The magnitude of the deficient phoneme (vowel and consonant contrasts) processing shown by M MN anomalies was proportionally related to the non-word. discrimination and did not interact with the word discrimination performance. The impact of d eficient speech sound processing on higher level processes may depend on th e type of aphasia, while the presence of perceptual deficits in processing acoustic/phonetic contrasts seems to be independent of the type of aphasia. (C) 2001 Elsevier Science Ltd. All rights reserved.