The purpose of this proposal is to respond to RFA-HD-04-027 by developing a multi-disciplinary research center on learning disabilities (LD), the Texas Center for Learning Disabilities. Consistent with the goals of RFA, we focus on definition and measurement issues, intervention in preventative (younger students) and remedial (older students) modes, and the neurobiological correlates of LD. The central theme is that RTI operationalizes the historically prominent component of the LD construct, "unexpected underachievement." Whereas approaches to identification typically have viewed performance on cognitive tests and the application of exclusionary criteria as the primary markers for "unexpected underachievement," such approaches have not been supported by classification research over the past two decades. Rather, it has become increasingly clear that "unexpected underachievement" can only be understood in children who have received high quality instruction and respond inadequately to instruction that is effective with most students. Thus, to establish a reliable and valid classification of LD, inadequate responders should be systematically studied from instructional, neurobiological, and cognitive perspectives. To accomplish these goals, we propose a multi-disciplinary center involving researchers with backgrounds in neuropsychology, cognitive neuroscience, reading intervention, special education, and methodology to work together in a LD Center that includes four Projects and three Cores. Project 1 (Classification) evaluates definition and classification issues pertinent to RTI models of identification, including the reliability and validity of classifications based on RTI. Project 2 (Early Intervention) provides randomized controlled studies of Grade 1 children at-riskfor reading difficulties, including enhanced reading instruction at a secondary level (Tier II) and more intense tertiary interventions for students who do not respond adequately to Tier II instruction. Project 3 (Remediation) involves randomized controlled trials of studies of middle schoolers with identified reading problems using a multi-tiered approach and tertiary interventions with students who do not respond to enhanced reading instruction at Tier II. Project 4 (Magnetic Source Imaging) will provide functional neuroimaging studies of reading component subtypes defined in Project 1, and the intervention outcomes in Projects 2 and 3. It specifically addresses the validity of RTI classifications, compares responders and inadequate responders, and evaluates response to tertiary interventions. The Cores include the Administrative Services Core (A), the Database and the Statistics Core (B), and the Dissemination Core (C). This research center will support research that leads to a more comprehensive classification of LD, a more integrated understanding of intervention at different levels and intensities for children with reading problems, and provide important cross-discipline insights into the nature of LD.