DEVELOPMENT OF CEREBRAL SPECIALIZATIONS

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Our long-term objectives are to study the roles of early sensory experience and early language experience in neural and behavioral development. We will record event-related potentials (ERPs) from over several brain regions while deaf and hearing subject (Ss) process different kinds of sensory, cognitive and language information. Behavioral and ERP measures will be employed to investigate the functional organization of the remaining sensory modalities in individuals who have been deaf since birth to assess the hypothesis that these systems display compensatory increases in activity as a consequence of unimodal deprivation. Additionally, we will assess behavioral and ERP indices of the different functional specializations of the left and right cerebral hemispheres during the performance of language tasks to determine those aspects that may develop with the acquisition of all formal languages, regardless of their structure and modality, and other aspects which may be determined by the age of language acquisition and processing demands of the primary language. We will separately assess the effects of auditory deprivation and acquisition of a visual language by comparing results from normally hearing subjects (Ss), congenitally deaf Ss whose first language is American Sign Language (ASL) and normally hearing Ss, born to deaf parents, whose first language is ASL. In order to investigate the possibility that there are sensitive or critical periods when sensory and language experience impact neural and behavioral development, we will study later-deafened individuals who learned ASL as a first language, and congenitally deaf Ss who acquired ASL at different times in development. In each of these populations we will assess cerebral organization during the detection and localization of visual and somatosensory stimuli, during tests of facial recognition, and during the processing of English and ASL. We will also assess the hypothesis that the processing of auditory and somatosensory information is enhanced in Ss blind since birth, and the possibility that the different cognitive experience and language experience of the blind may be associated with an altered pattern of functional specializations between the hemispheres. The proposed research is pointed, in the long run, toward an understanding of the optimal nature and timing of education for deaf and blind children, as well as for normally hearing/sighted children.