Their work, the first to identify specific brain mechanisms involved in a person's ability to overcome reading difficulties, could lead to new interventions to help dyslexics better learn to read.
"This gives us hope that we can identify which children might get better over time," said Fumiko Hoeft, MD, PhD, an imaging expert and instructor at Stanford's Center for Interdisciplinary Brain Sciences Research. "More study is needed before the technique is clinically useful, but this is a huge step forward."
Hoeft is first author of a paper, which will be published online Dec. 20 in the Proceedings of the National Academy of Sciences. The senior author is John Gabrieli, PhD, a former Stanford professor now at the Massachusetts Institute of Technology.
Dyslexia, a brain-based learning disability that impairs a person's ability to read, affects 5 to 17 percent of U.S. children. Affected children's ability to improve their reading skills varies greatly, with about one-fifth able to benefit from interventions and develop adequate reading skills by adulthood. But up to this point, what happens in this brain to allow for this improvement remained unknown.
Past imaging studies have shown greater activation of specific brain regions in children and adults with dyslexia during reading-related tasks; one area in particular, the inferior frontal gyrus (which is part of the frontal lobe), is used more in dyslexics than in typical readers. As the researchers noted in their paper, some experts have hypothesized that greater involvement of this part of the brain during reading is related to long-term gains in reading for dyslexic children.
For this study, Hoeft and colleagues aimed to determine whether neuroimaging could predict reading improvement and how brain-based measures compared with conventional educational measures.
The other exciting implication, Hoeft said, involves therapy. The research shows that gains in reading for dyslexic children involve different neural mechanisms and pathways than those for typically developing children. By understanding this, researchers could develop interventions that focus on the appropriate regions of the brain and that are, in turn, more effective at improving a child's reading skills.
Hoeft said this work might also encourage the use of imaging to enhance the understanding (and potentially the treatment) of other disorders.
"In general terms, these findings suggest that brain imaging may play a valuable role in neuroprognosis, the use of brain measures to predict future reductions or exacerbations of symptoms in clinical disorders," she explained.
The authors noted several caveats with their findings. The children were followed for two-and-a-half years; longer-term outcomes are unknown. The study also involved children in their teens; more study is needed to determine whether brain-based measures can predict reading progress in younger children.
Hoeft is now working on a study of pre-readers, being funded by the National Institute of Child Health and Human Development.
- Fumiko Hoeft, Bruce D. Mccandliss, Jessica M. Black, Alexander Gantman, Nahal Zakerani, Charles Hulme, Heikki Lyytinen, Susan Whitfield-Gabrieli, Gary H. Glover, Allan L. Reiss, and John D. E. Gabrieli. Neural systems predicting long-term outcome in dyslexia. Proceedings of the National Academy of Sciences, 2010; DOI: 10.1073/pnas.1008950108