The purpose of the present study was to examine patterns of neural activity relevant to language processing in 20-month-old infants, and to determine whether or not changes in cerebral organization occur as a function of specific changes in language development. Event-related potentials (ERPs) were recorded as children listened to a series of words whose meaning was understood by the child, words whose meaning the child did not understand, and backward words. The results showed that specific and different ERP components discriminated comprehended words from unknown and from backward words. Distinct lateral and anterior-posterior specializations were apparent in EW responsiveness to the different types of words. Moreover, the results suggested that increasing language abilities were associated with increasing cerebral specialization for language processing over the temporal and parietal regions of the left hemisphere.

Clinical, behavioral, and neurophysiological studies of developmental language impairment (LI), including reading disability (RD), have variously emphasized different factors that may contribute to this disorder. These include abnormal sensory processing within both the auditory and visual modalities and deficits in linguistic skills and in general cognitive abilities. In this study we employed the event-related brain potential (ERP) technique in a series of studies to probe and compare Merent aspects of functioning within the same sample of LI/RD children. Within the group multiple aspects of processing were affected, but heterogeneously across the sample. ERP components linked to processing within the superior temporal gyrus were abnormal in a subset of children that displayed abnormal performance on an auditory temporal discrimination task. An early component of the visual ERP was reduced in amplitude in the group as a whole. The relevance of this effect to current conceptions of substreams within the visual system is discussed. During a sentence processing task abnormal hemispheric specialization was observed in a subset of children who scored poorly on tests of grammar. By contrast the group as a whole displayed abnormally large responses to words requiring contextual integration. The results imply that multiple factors can contribute to the profile of language impairment and that different and specific deficits occur heterogeneously across populations of LI/RD children.