Although there is a vast research literature on learning disabilities (LD), experts cannot agree on answers to the questions asked most frequently by parents and teachers, namely, does the child have a learning disability and, if so, what is the problem and what can be done about it. A fundamental premise of the proposed Center is that LD is a disorder of neurodevelopment, not a disorder of specific skill acquisition. Questions to be addressed by the research program are: what neurodevelopmental characteristics can reliably distinguish LD children from non-LD children and what characteristics distinguish these children from one another. The central hypothesis to be tested is that rapid processing of temporal information is specifically disordered in LD children. We will evaluate various aspects of low-level information processing by means of coordinated studies of auditory, visual and motor behavioral paradigms, quantitative EEG and functional MRI in order to elucidate the fundamental "building blocks" of central nervous system function that are associated with LD. These will be examined in relation to the higher order features of cognition, academic performance, and social adaptation that are of greatest clinical concern. The Center comprises three Cores (Administrative, Neurobehavioral Assessment, and Human Subjects and Data Management/Biostatistics) and five projects. ,All are focussed on a single cohort of LD children, and each addresses a different level of neurobehavioral analysis. The study sample will include LD children between the ages of 8 and 11 years (N = 200) and a standardization sample of same age children (N=200). Goals of the program include (1) to determine to what extent LD children can be differentiated from a normative sample by characteristics of their low level information processing; (2) to evaluate the reliability and validity of low level information processing "signatures" of LD; (3) to define the neural "building blocks" that are associated with LD. It is anticipated that a more thorough understanding of these "building blocks" will provide a basis for novel approaches to the treatment of this disorder.