Processing semantic and grammatical information in auditory sentences: Electrophysiological evidence from children and adults

To fully understand the words spoken by our fellow humans, a complex integration process needs to occur that takes into account both the meaning provided by the words (semantics) and the information conveyed by the structural relations between words (grammar). A current quest of neurolinguists is to understand how these two types of information interact during sentence processing and to examine how this relationship is represented physiologically within the brain.; In this dissertation, event-related brain potentials (ERPs) were used to examine how semantic and grammatical information within speech is processed in the adult and toddler brain. In the first study, ERPs were recorded while adults listened to naturally spoken sentences in which the semantic and (three types of) grammatical information was manipulated. The results indicated that processing each of the four types of linguistic information elicited distinct patterns of brain activity. Moreover, these results replicated those found in previous visual studies and suggest that non-identical neural systems mediate the processing of semantic and grammatical information.; But how and when do these specialized processed develop? In the second study, ERPs were recorded while children 32--38 months of age with varying linguistic competencies listened to child-friendly sentences in which the semantic and grammatical information was experimentally manipulated. The results of this study suggested that semantic and grammatical information are already processed by non-identical neural systems in high- but not average-proficiency children 32--38 months of age.; The third study was designed to more closely examine how toddlers process grammatical information within sentences. By manipulating the semantic content of the stimuli (via English and Jabberwocky sentences), it was possible to directly evaluate the interaction of semantic and grammatical information during sentence comprehension. The data indicated that high-comprehending 36- to 39-month-olds do not require semantic information to perform the grammatical parse, but that---when available---they use meaning to facilitate the process.; Overall, this set of studies provides evidence that in adults semantic and grammatical information are processed by non-identical, specialized regions within the language systems of the brain. The data further suggest that this specialization is driven by increases in linguistic proficiency and begins as early as 36 months of age in high-comprehending children.; This dissertation includes some material which will be published with co-authors.