Using functional MRI, researchers have identified neurobiological changes that may help explain differences in reading acquisition between children with and without dyslexia. Using functional MRI, researchers have identified neurobiological changes that may help explain differences in reading acquisition between children with and without dyslexia.

"Our findings indicate that the neural systems for reading that develop with age in nonimpaired readers differ from those that develop in dyslexic readers," Dr. Bennett A. Shaywitz, from Yale University School of Medicine in New Haven, Connecticut, and colleagues write. "The most significant contrasts focus on those systems within the left occipitotemporal area."

The findings, which appear in the Annals of Neurology for April, are based on a study of 113 dyslexic and 119 nonimpaired readers, all of whom were right-handed and between the ages of seven and 18 years. Functional MRI was used to measure age-related changes in reading neural systems as the subjects read pseudowords.

As nonimpaired readers aged, increasing development in the left anterior lateral occipitotemporal area was noted, while development in the right superior and middle frontal regions decreased. By contrast, with age, dyslexic children showed increased development of the left posterior medial occipitotemporal regions.

Left lateralization in the anterior lateral occipitotemporal area was noted in older nonimpaired readers. In dyslexic readers, no asymmetry differences were noted between younger and older subjects.

Data from prospective, longitudinal studies are needed to confirm and expand on the current findings, the authors conclude.