Bases of Normal and Disordered Reading

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DESCRIPTION (provided by applicant): This proposal is a competing continuation of a previous grant, "Perceptual, linguistic, and computational bases of dyslexia." The focus of our research was on using a connectionist model of reading to frame empirical studies of reading acquisition and dyslexia, with an emphasis on identifying subtypes associated with different underlying impairments. During the previous granting period, we conducted a longitudinal study of reading acquisition and dyslexia and behavioral experiments concerning speech perception, spelling, and learning targeted at identifying possible causes of dyslexia. We also completed a major extension of the Seidenberg and McClelland (1980) model to developmental dyslexia and implemented a model of the computation of word meaning from print. The behavioral research suggests that there are phonological and non-phonological bases for dyslexia which produce different behavioral profiles that are stable over time. Overt speech recognition deficits were only observed in a subset of phonological dyslexics with broader language impairments. Thus the studies suggest that phonological impairments can be severe enough to impact reading negatively but leave speech perception unaffected. In the next granting period we propose to conduct new experiments focused on the nature of the impairments in phonology, speech and visual perception that have been observed in dyslexics, the effects of these impairments on reading behavior, and whether different brain activation patterns underlie different subtypes. The research program involves using behavioral experimentation, computational modeling, and neuroimaging techniques to develop a unified account of normal and disordered reading. The studies are likely to yield advances with regard to theories of reading, the bases of reading impairments, basic aspects of normal and disordered speech and visual perception, and the brain bases of reading ability and disability.