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

The mismatch negativity component (MMN) of auditory event-related potentials (ERP) was recorded in four aphasic patients and in age, gender and education matched controls. The MMN changes elicited by tone, vowel, voicing stop consonant and place-of articulation contrasts were recorded over both hemispheres. The results of MMN amplitude, latency and distribution differences between aphasics and controls were analyzed in detail. An extensive neuropsychological investigation was performed in order to highlight the assumed dissociation 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 to distinguish between patients and age-matched controls. The MMN elicited by consonant contrasts was found to be the most vulnerable in aphasic patients investigated. The MMN elicited by voicing ([ba:] vs. [pa:]) and place-of-articulation ([ba:] vs. [ga:]) could be characterized by total lack, distorted or very limited distribution and correlated with the patients' performance shown in the behavioral phoneme discrimination task. The magnitude of the deficient phoneme (vowel and consonant contrasts) processing shown by MMN anomalies was proportionally related to the non-word discrimination and did not interact with the word discrimination performance. The impact of deficient speech sound processing on higher level processes may depend on the type of aphasia, while the presence of perceptual deficits in processing acoustic/phonetic contrasts seems to be independent of the type of aphasia.

Speech perception and speech comprehension investigations of pre-term newborns and high-risk neonates of pre-school age

The purpose of this study is to establish whether there is any connection between neonatal morbidity and speech perception and comprehension in children of pre-school age who have previously been treated as newborn infants in an intensive care unit. The test applied is a method invented in Hungary for the analysis of global hearing, speech perception and comprehension. The authors summarize the results of their follow-up studies of 52 children with respiratory disorders as newborns, some of whom were born as pre-term and some as full-term newborns with asphyxia. The children have been put into three groups according to their maturity and their birthweight. Newborns with hearing loss and mental retardation were excluded from this study. Of the various neonatal factors the results show: complications of delivery, birthweight, hypoxia, persistent ductus arteriosus, duration of ventilation and complications of respiratory treatment are found to be correlated to perception and comprehension. Incidences of poor achievement obtained in the most characteristic subtests have been compared among the different groups of newborns. The intelligence level of pre-school children is found to be closely correlated to speech perception and comprehension.