The long term objectives of this project are to study biological constraints and the role of experience in the differentiation of the neural systems relevant to language and cognitive processing. Our approach will be to compare cerebral organization during language and non-language cognitive tasks in normally developing children at different ages (from 4- 19 years) and stages of language and cognitive development. Additional comparisons of children who are specifically language impaired (LI) and reading-disabled (RD) will aid in the separation of age-related and language-specific aspects of neural development and will also permit an assessment of the neurobehavioral functions that have been implicated in the deficits that LI/RD subjects (Ss) display. We will record event-related brain potentials (ERPs) from over several regions within and between the hemispheres as these children process sensory, cognitive and language information in tasks designed to modulate different and specific types of processing. The three series of experiments will assess several hypotheses including: I. Language: 1. The timecourse of differentiation of the neural systems important in grammatical proCessing is more prolonged than is that linked to semantic processing and these systems develop abnormally in a subset of LI/RD children. 2. The systems active during phonological processing develop over a protracted developmental timecourse and the subset of LI/RD subjects who display auditory processing deficits display anomalous development of these systems. 3. Highly specialized, automatically activated language systems are absent or function abnormally in LI/RD subjects. Il. Visual Processing: 1. Basic sensory processing within the magno/dorsal visual pathway are selectively impaired in LI/RD children. 2. LI/RD children display deficient mechanisms of spatial attention within the dorsal visual pathway. 3. Aspects of face perception that are dependent on ventral pathway function develop early in normal children and are intact in LI/RD children. 4. The specialization of neural systems within the right hemisphere occurs along a prolonged timecourse that follows and is dependent upon specialization of the left hemisphere for language. Ill. Audition: The subset of LI/RD children who display auditory processing deficits also have deficient auditory attentional capabilities. Since these studies will evaluate periods in development when the acquisition of specific skills has its greatest impact they will, in the long run, provide information of practical significance for developing, refining and evaluating educational programs for both normally developing and language-impaired individuals.
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