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We review the evolution of the conceptualisation of dyslexia and along with it the current, 21st century definition of dyslexia. Our starting point is the seminal report by Pringle Morgan in 1896, followed by early 20th century reports by Hinshelwood, and continuing with concepts of brain injury and minimal brain dysfunctions then to the emergence of 'learning disability' in the mid-20th century. Within this historical framework we note the emergence and scientific validation of an 'unexpected' model culminating in the first definition of dyslexia in U.S. federal law in late 2018 and in recent U.S. federal civil rights law. We next address the issue of whether dyslexia is 'real' by showing how advances in non-invasive functional brain imaging have led to a replicated, robust neural signature for dyslexia. We close by illustrating how science has informed policy, emphasising the focus on evidence-based practices beginning with the report of the National Reading Panel and including the creation of the What Works Clearinghouse. Early screening for dyslexia represents another important policy accomplishment with dyslexia laws now passed in over 30 states. Evidence-based effective interventions for dyslexia, including free, public charter schools specialised for dyslexic children exemplify the most recent policy initiative. [ABSTRACT FROM AUTHOR]

Converging evidence from a number of lines of investigation indicates that dyslexia represents a disorder within the language system and more specifically within a particular subcomponent of that system, phonological processing. Recent advances in imaging technology, particularly the development of functional magnetic resonance imaging (fMRI), provide evidence of a neurobiological signature for dyslexia, specifically a disruption of 2 left hemisphere posterior brain systems, 1 parietal-temporal, the other occipital-temporal, with compensatory engagement of anterior systems around the inferior frontal gyrus and a posterior (right occipital-temporal) system. Furthermore, good evidence indicates a computational role for the left occipital-temporal system: the development of fluent (automatic) reading. In addition, fMRI studies of young adults with reading difficulties followed prospectively and longitudinally from age 5 through their mid 20s suggests that there may be 2 types of reading difficulties, 1 primarily reflecting a genetic basis, the other, and far more common, reflecting environmental influences. The brain systems for reading are malleable and their disruption in children with dyslexia may be remediated by provision of an evidence-based, effective reading intervention. These studies offer the promise for more precise identification and effective management of dyslexia in children, adolescents, and adults. [ABSTRACT FROM AUTHOR]

This paper attempts to model the development of children's reading skills using the negative exponential curve with mixed effects model. The model describes the nature of growth in children's reading skills and accounts for intra-individual and inter-individual variations. In addition, we propose methods including cross-validation, regression, and graphing to determine an appropriate curve for the data, to find good initial values for parameters, and to select potential covariates. We illustrate with an example that motivated this research: a longitudinal study of academic reading skills from grade 1 to grade 12 in Connecticut public schools. [ABSTRACT FROM AUTHOR]