Age-Related Changes in Reading Systems of Dyslexic Children Bennett A. Shaywitz, MD, 1,2 Pawel Skudlarski, PhD, 3 John M. Holahan, PhD, 1 Karen E. Marchione, RN, 1 R. Todd Constable, PhD, 4 Robert K. Fulbright, MD, 4 Daniel Zelterman, PhD, 5 Cheryl Lacadie, BS, 4 and Sally E. Shaywitz, MD 1 Objective: To examine age-related changes in the neural systems for reading in nonimpaired and dyslexic children and ado- lescents. Methods: Functional magnetic resonance imaging was used to study age-related changes in the neural systems for reading in a cross-sectional sample of 232 right-handed children 7 to 18 years of age (113 dyslexic readers and 119 nonimpaired readers) as they read pseudowords. Results: In nonimpaired readers, systems in the left anterior lateral occipitotemporal area developed with age, whereas systems in the right superior and middle frontal regions decreased. In contrast, in dyslexic readers, systems in the left posterior medial occipitotemporal regions developed with age. Older nonimpaired readers were left lateralized in the anterior lateral occipitotem- poral area; there was no difference in asymmetry between younger and older dyslexic readers. Interpretation: These findings offer a possible neurobiological explanation for the differences in reading acquisition between dyslexic and nonimpaired readers and provide further evidence of the critical role of the left occipitotemporal region in the development of reading. Ann Neurol 2007;61:363–370 Converging evidence from a number of lines of inves- tigation points to three important neural systems for reading in children and adults: one anterior system around the inferior frontal gyrus involved in word analysis (decoding); and two posterior systems, one in the parietotemporal region also involved in word anal- ysis, and the other more inferior in the occipitotempo- ral region responsible for skilled, fluent (automatic) reading. Much of this information has come from functional brain imaging studies that compare nonim- paired readers with dyslexic readers. These investiga- tions have consistently demonstrated a failure of left- hemisphere posterior brain systems to function properly in dyslexic readers. 1–12 Despite the consistency of data in posterior reading systems, relatively little is known about the development of these systems in typical readers, and even less is known of the development of these systems in dyslexic children. The approach used in this study builds on the accumulating evidence that the central difficulty in dyslexia reflects a deficit within the language system, and more particularly, in a lower level component, phonology, which has to do with the ability to access the underlying sound structure of words. 13 Although previous studies 14,15 have reported age- related changes in activation patterns, each study has come to different conclusions as to which specific brain regions are involved in the development of reading. We hypothesized that the development of a specific neural system located within the left occipitotemporal region accounts for the development of fluent reading in nonimpaired readers. We also hypothesized that this system does not develop with age in dyslexic readers, and that dyslexic readers rely on an alternative neural pathway for reading. This study was motivated by the belief that elucidation of the specific systems develop- ing with age in nonimpaired and dyslexic readers would provide insights into potentially differing mech- anisms used for reading in each group. In this study, we examined the development of neu- From the 1 Department of Pediatrics, Section of Pediatric Neurol- ogy; 2 Department of Neurology, Yale University School of Medi- cine, New Haven; 3 Olin Neuropsychiatry Research Center, Institute of Living, Hartford; Departments of 4 Diagnostic Radiology and 5 Epidemiology and Public Health, Yale University School of Med- icine, New Haven, CT. Received Jun 25, 2006, and in revised form Jan 9, 2007. Accepted for publication Jan 10, 2007. This article includes supplementary materials available via the Inter- net at http://www.interscience.wiley.com/jpages/0364-5134/supp- mat Published online Apr 24, 2007 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/ana.21093 Address correspondence to Dr Shaywitz, Department of Pediatrics, Section of Pediatric Neurology, Yale University School of Medicine, PO Box 3333, New Haven, CT 06510-8064. E-mail: bennett.shaywitz@yale.edu © 2007 American Neurological Association 363 Published by Wiley-Liss, Inc., through Wiley Subscription Services