In the first known study of its kind, researchers have identified brain activity that links dyslexia to difficulty with math. The findings from the Georgetown University Medical Center study are published in the Nov. 1 issue of the journal NeuroImage, now online.

People typically associate dyslexia with reading problems. However, those with dyslexia can also struggle with specific math problems, even though they may not meet the criteria for a formal math disability diagnosis (dyscalculia). The researchers say the finding has important ramifications for recognizing the wide spread repercussions of dyslexia.

"It is known that the incidence of math disability is higher in children who have a reading disability," says senior author Guinevere Eden, PhD, director of Center for the Study of Learning at Georgetown University Medical Center. "It has also become clear that specific aspects of arithmetic - those involving retrieval of verbal information - are difficult for children and adults with dyslexia."

To understand this relationship between math performance and reading disability, the researchers had to go beyond studying children's behavior and take a closer look at their patterns of brain activity while doing math.

"Children without dyslexia show more activity for subtraction compared with addition in the right intraparietal sulcus, a region known to be important for calculation," says lead author Tanya Evans, PhD, now a fellow at Stanford University School of Medicine. "Children with dyslexia show equal activity in this region, suggesting they are using a similar strategy to perform these different tasks. This strategy is probably not ideal and a reason for the previously observed poorer performance during addition."

The findings highlight that reading is not the only skill affected by dyslexia, which has important implications for education. Previous work looking at performance measures has demonstrated this weakness in people with dyslexia for math problems that are normally solved through fact retrieval (e.g., small digit addition and multiplication, such as 2+3, or 5x5), relative to those more likely to be solved using formulas or other strategies (e.g., subtraction, division).

"This could impact the strategies used for interventions to target this common learning disability," says Eden. "Interventions targeting verbal retrieval may be helpful in bolstering arithmetic skills in children that struggle with reading."