GAINESVILLE---Brain structure and hand preference may be as important as environment in influencing a child's ability to learn to read, according to a University of Florida Brain Institute study.
The seven-year study of 39 Alachua County students from kindergarten to sixth grade indicates that while children from a lower socioeconomic class may be at risk for reading failure, the detrimental effects of environment are greatly increased in children with unusual brain asymmetry.
"This is the first study of students with a broad range of reading ability which shows that both brain structure and environment are related to the acquisition of skills critical for learning to read," said Mark Eckert, the UF psychobiology graduate student who designed the study. "It also is the first study to show that brain structure is related to the rate of reading skill development."
Eckert will present the preliminary research findings at the annual meeting of the Society for Neuroscience in Los Angeles on Nov. 9, and at the International Dyslexia Association meeting in San Francisco on Nov. 13. Christiana Leonard, a professor of neuroscience in UF's College of Medicine, and Linda Lombardino, a professor of communication sciences and disorders in the College of Liberal Arts and Sciences, are collaborators on the project. All three are members of the UF Brain Institute.
Students in the study were tested in kindergarten and first grade for tasks that are known predictors of reading success, including the ability to rhyme, spell and reverse the order of speech sounds. Hand preference was tested with a questionnaire asking how often each hand is used to perform tasks such as throwing a ball or brushing teeth. If a child performed two or more tasks with either hand, they were classified as nonright-handed, meaning they were left-handed or didn't have a hand preference.
In sixth grade, students were given the same reading tests they took in first grade. They also received a magnetic resonance imaging scan of their head to measure brain structures. Those measurements then were compared to reading skills performance.
Using the MRI scans, researchers measured the size of the temporal plane on both sides of the brain, an area believed to play a role in language development. Results indicate reading skill performance is dependent on the relationship between hand preference and the direction of brain asymmetry.
Right-handed students whose left temporal plane was larger than the right demonstrated superior reading skills when they came from an average or high socioeconomic environment. Right-handed children with reversed asymmetry were at risk for reading failure, especially if they came from a poor family.
Socioeconomic status was determined by whether students received free or reduced-price school lunch. Students receive this subsidy if their family's yearly income is below a federally defined level. Researchers in the UF study found poverty was related to parental reports of fewer hours of homework help each week, fewer books in the home and a lower parental education level.
"A child who doesn't have the preferred brain symmetry-hand dominance relationship and who comes from a family that provides minimal literacy stimulation is at greater risk for a reading disorder than a child with a similar brain-hand dominance relationship who has had more exposure to literacy stimulation in the home," said Lombardino, who collected data from the kindergartners in 1992.
Most people are right-handed and have a larger temporal plane in the left hemisphere of the brain, called left asymmetry. Studies show that left-handed people are more likely to have a larger temporal plane in the right hemisphere of the brain.
In this study, researchers found leftward brain asymmetry was related to strong recognition of speech sounds and rightward asymmetry was related to poor recognition of speech sounds in right-handed children. Leftward brain asymmetry was not an advantage in children who did not have a strong right-hand preference. Left-handed children with left asymmetry were at risk for reading failure.
The only children in this study who demonstrated above-average reading skills came from an average or above-average environment and had asymmetry appropriate for their hand preference, meaning a larger structure in the hemisphere opposite to the preferred hand.
"This is a new concept for people, that learning ability could depend on brain structure," Leonard said. "I think it's important to note that there were no anatomical differences in children from different socioeconomic environments. But if a child has reversed asymmetry, improving the literacy environment becomes especially important."
Funding for the study came from the National Institutes of Health and the International Dyslexia Association.
(For more information, call Paul Ramey, Health Science Center Office of
Public Information, 352/392-3845 or e-mail: pramey@ufl.edu)