Converging evidence from a number of neuroimaging studies suggests that skilled reading is related to the development of a highly organized integration of orthographic, phonological and lexical-semantic features of words involving two consolidated left hemisphere (LH) posterior reading circuits: a dorsal (temporo-parietal) circuit and a ventral (occipito-temporal) circuit. These posterior reading circuits are dysfunctional in reading disabled (RD) readers. In apparent compensation for this LH posterior anomaly RD readers show 1) increased reliance on inferior frontal gyrus (IFG) during reading and 2) an increased tendency to engage the RH homologues of the disrupted LH posterior circuits. In this proposal, using both fMRI and behavioral measures, we examine whether in RD children the compensatory reliance on inferior frontal gyrus (IFG) and RH posterior areas reflects a processing dissociation between phonological and semantic dimensions at the level of functional brain organization. Confirmation of this dissociation account using both fMRI and behavioral measures will provide a foundation for better understanding the specific deficits evident in RD children during word and pseudoword reading and a framework for interpreting changes in functional organization associated with development and/or remediation. Additionally, this project examines the effects of factors such as practice and contextual support (e.g., reading words in sentential context and priming effects) in non-impaired and RD readers. These factors have demonstrable ameliorative effects on word reading accuracy in RD children. In the proposed fMRI experiments, we address the question of whether these facilitatory influences will tend to normalize the anomalies in LH posterior reading circuits in RD readers. If differences between NI and RD readers with respect to dissociation or consolidation at a neurobiological level are reduced by any or all of these reading variables, these findings would directly impact on our understanding of the mechanisms by which remediation and training will have their influences on reading development.
