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BRAIN AREAS INVOLVED IN READING CHANGE DURING DEVELOPMENT
"This study directly compares simple word reading across the age range from school children to adulthood," says principal investigator Bradley L. Schlaggar, M.D., Ph.D., assistant professor of neurology, of radiology, of anatomy and neurobiology and of pediatrics. "By helping us understand how healthy individuals develop language abilities, these data may ultimately be useful in improving early diagnosis of language disorders and in developing effective interventions." Developed in the last decade, fMRI allows scientists to take pictures of blood flow in the brain to see which regions are involved in different tasks. In the past, experts believed it was difficult, if not impossible, to compare brain activation between children and adults. But in a 2002 study published in the journal Science, Schlaggar's team presented new approaches for comparing fMRI results in children and adults and evidence that those approaches may offer valid, useful insights. For example, the team used tasks that involve responding out loud, allowing them to only use brain images taken during correct responses made in about the same amount of time for all participants. By focusing only on responses matched for accuracy and speed, the researchers argue that their comparisons reveal maturational differences and similarities in brain activity as opposed to differences in individual skill levels. Because talking forces the head to move, which in turn may compromise the clarity of brain images, the group also employed a relatively new method of analyzing imaging results called event-related fMRI, developed in part by researchers at Washington University. The technique allows scientists to individually analyze images that correspond to the exact moment a response is made and omit images distorted by head movements. Incorporating these same methodological strategies, Schlaggar's teamed compared fMRI scans from 30 children (7 to 10 years old), 24 adolescents (11 to 17 years old) and 21 adults (19 to 35 years old) taken while participants read single words aloud. The amount of brain activity in 17 regions differed between the three groups. Activity in some brain regions gradually decreased with age, they were the most active in the youngest age-group and were least active in the adult group. Those regions include the bilateral precuneus and posterior cingulate located toward the back of the brain and the middle temporal gyrus on the surface of the left side of the brain. Other regions, including the anterior cingulate in the front of the brain and the left caudate located deep within the brain, were deactivated (presumably inhibited) in adults but did not change in activation in children. According to Schlaggar, "These results suggest that brain function during simple word reading differs across the various stages of development, independent of skill level." His team is examining brain activity during this reading task in children who have had a stroke and plans to expand the research to children with developmental dyslexia. "By comparing patient populations to normal children and adults, we hope to better understand the developing brain and its disorders, particularly those that are related to language," he says.
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