  This symposium, held March 12, 1999, examined what areas of the brain are involved in reading. Through the use of imaging machines, the speakers were able to identify differences in the brains of people with reading deficits and those without deficits. These findings have important implications for our understanding of how the brain functions during reading. Reading and the Brain: Cognitive and Neurobiological Influences in Reading and Dyslexia Many lines of research indicate that reading is dependent upon the language system. There is now a strong consensus that the central difficulty in dyslexia is a difficulty with a specific component of the language system. This component, the phonological module, is engaged in processing the sounds of speech. According to this phonological-deficit hypothesis, individuals with dyslexia have difficulty developing an awareness that words, both written and spoken, can be broken down into smaller units of sound. They do not attribute the letters of the printed word to the sounds heard in the spoken word. As a result, the reader experiences difficulty, first in decoding the word and then in identifying it. This occurs even when cognitive and linguistic functions involved in comprehension, vocabulary and syntax are intact. Two recent advances help localize the brain mechanisms involved in phonological processing. The first is the development of tasks that isolate the subcomponent processes of reading. The second is the development of imaging technology, particularly functional magnetic resonance imaging (fMRI). Most recently, we used fMRI to compare patterns of brain activity in readers with dyslexia and those without dyslexia during progressively more difficult tasks of phonologic analysis. Brain activation patterns differed significantly between the groups. Dyslexic readers showed relative underactivation in some parts of the brain (posterior regions) and relative overactivation in a different part of the brain (an anterior region). Two conclusions can be drawn from this finding. First, the impairment in dyslexia is phonologic in nature. Second, this impairment may produce a specific brain activiation pattern or neural signature. These results offer the future promise for more precise identification and diagnosis of dyslexia in children, adolescents and adults. Sally E. Shaywitz, M.D., has examined reading and dyslexia from a broad perspective including epidemiology, cognitive influences and, most recently, their neurobiologic underpinnings. Dr. Shaywitz is Co-Director of the Yale Center for the Study of Learning and Attention and Professor of Pediatrics at the Yale School of Medicine. She is a member of the Institute of Medicine of the National Academy of the Sciences. Bennett A. Shaywitz, M.D., uses functional magnetic resonance imaging (fMRI) to investigate the neurobiologic mechanisms underlying reading and dyslexia, and the relationship between dyslexia and attention deficit hyperactivity disorder (ADHD). He is Co-Director of the Yale Center for the Study of Learning and Attention and Professor of Pediatrics and Neurology at the Yale University School of Medicine. more information on Sally E. Shaywitz, M.D. or Bennett A. Shaywitz, M.D. |
