The long-term objectives of this project are to identify whether there are any structural differences that distinguish the brains of children or adults with developmental reading disorders (dyslexia) and how these differences correspond to behavioral heterogeneity in reading impairment across development. Dyslexia is a neurodevelopmental disorder that specifically and often profoundly impairs the ability to acquire accurate and fluent reading skills. However, decades of research have failed to converge on one or more signature differences in the brains of children or adults with dyslexia that reliably, sensitively, or specifically distinguish impaired versus typical reading development. Drawing from numerous independent datasets collected by the investigators' labs over the past decade, this project will assemble and analyze the largest sample of structural brain scans ever studied from children, adolescents, and adults with developmental dyslexia and typical reading development. This combined dataset includes over 1200 structural brain scans obtained from individuals between the ages of 4 and 40 years old, for whom extensive reading and cognitive assessments were performed, and approximately 50% of whom have dyslexia. This dataset will be used to address two aims:
In Aim 1, this study will explore whether structural brain features differ between individuals with and without dyslexia. Features to be studied include (1) macroanatomical morphology of the temporal lobe, such as patterns of Heschl's gyrus reduplication or planum temporale lateralization; (2) regional morphometric differences in gray or white matter volumes or their lateralization; and (3) geometric differences in cortical thickness, curvature, and surface area. Variation in these features will also be analyzed in the context of component reading skills, such as phonological awareness and rapid naming.
In Aim 2, this study will use the processed dataset to build a model of the developmental trajectory of brain maturation in dyslexia compared to typical reading. This model will be used to evaluate current theories about developmental versus endogenous factors affecting reading impairment. Identifying the neuroanatomical substrate or substrates that are related to reading impairment, and how these change across development, is a key step in understanding the biological basis of dyslexia. A stronger scientific understanding of the causes and prognosis of developmental reading impairments will build a foundation upon which diagnoses can be obtained both earlier and with greater specificity, and upon which behavioral interventions can be deployed more efficaciously, ultimately to ensure that all children have the chance to achieve their full potential for healthy and productive lives.
Children with developmental dyslexia struggle with learning to read compared to their peers, despite having adequate intelligence, motivation, and educational opportunity. The difficulties that children with dyslexia experience when they are learning to read are thought to be the result of differences in their brains, but it is not currently well understood just what those differences are. This project will study the largest sample ever assembled of brains scans from children and adults with and without dyslexia to try to discover whether there are structural and developmental differences in the brains of individuals with dyslexia that may be part of why they have greater difficulties learning to read.
