Are we looking for dyslexia too late?
Ongoing research at Boston Children’s Hospital shows that brain imaging and a child’s family history of dyslexia, among a multifaceted array of other factors, can point to a predisposition for dyslexia well before that child ever steps foot in a kindergarten classroom. For schools and parents, this opens the possibility that struggling readers could receive interventions from the very start of their educational careers, offering them a better chance to succeed as learners and readers.
Dyslexia is by far the most common reading disability, affecting between five and 10 percent of the population. But its diagnosis currently follows a “failure model”: A child has to try and fail to read for several years before being diagnosed. Most children in the United States do not get diagnosed with dyslexia until the end of second grade or, more likely, the beginning of third.
This is the dyslexia paradox. Research has shown that reading interventions are most successful in kindergarten and first grade. By the time they reach third grade and are old enough for a diagnosis, says researcher Nadine Gaab of the Harvard Medical School and the Harvard Graduate School of Education, many children may be far behind their peers — and too discouraged to fully catch up.
Reading relies on several neurological areas and functions, especially the occipitotemporal (visual processing) and temporoparietal (phonological processing) brain regions. The gray matter in these regions and the white matter “highways,” or fiber bundles connecting the regions, work together to form the reading network. One vital bundle is the arcuate fasciculus, which connects the back of the reading network (mapping language sounds onto their written counterparts) to the frontal regions (reading fluency and comprehension).
For children with dyslexia, certain components of this network are simply not as strong. Gray matter may be less dense, and the highway of the arcuate fasciculus is less effective. “It could be smaller, or have reduced myelination, meaning it’s less fast, or it could have more crossing fibers, meaning there’s more ‘traffic lights,’” explains Gaab. When children with dyslexia open a book, the information traveling back and forth within the reading network gets slowed down or constricted along the way.
Gaab’s research team has conducted longitudinal and cross-sectional studies examining babies, preschool children, kindergarteners, and first-, second-, and third-graders. All the research has shown that these disparities in neurological function can exist not only for readers, but also for pre-readers as well.
In the Research on the Early Attributes of Dyslexia (READ) study, which the Gaab Lab completed with the Gabrieli Laboratory at MIT, researchers tested more than 1,500 kindergarteners for early signs of dyslexia. Using behavioral and language assessments and MRI scans, the study found that the volume of the children’s arcuate fasciculus correlated with their pre-reading skills. And all of these children were tested within the first six weeks of kindergarten — at only the very beginning of any type of reading instruction.
In Project BOLD (Boston Longitudinal Dyslexia Study), the Gaab Lab found that they could predict reading performance for still younger children. The disorder is largely hereditary; children with an older sibling or parent with dyslexia have a 50 percent chance of developing the disorder themselves. The researchers studied MRI scans of preschool-age children and found that those with a family history of dyslexia were less likely to demonstrate activation during phonological processing and more likely to show decreases in gray matter than kids without that family history. These two groups also show differences in the topography of the cortex, which is fixed from birth. Furthermore, the rate of development of the white matter highways differed in children based on whether they tested as good or poor readers years later.
These discrepancies exist even in infants. In a study of babies between four and 18 months, the Gaab Lab found that the arcuate fasciculus in babies with an older sibling or parent with dyslexia had less integrity than babies without that familial predisposition.
“It’s most likely children are born with a sub-optimal brain for learning to read,” explains Gaab, “but still we wait until they turn nine years old to give them a diagnosis.”
Earlier interventions could change the lives of millions of children — but changing the public policy approach to dyslexia is a huge challenge for schools. In the READ study, Gaab and her team not only screened incoming kindergarteners, but they also offered a report for each child, reading strategies for teachers, information nights for parents, and “brain awareness days” for the schools. But some schools, the researchers learned, did not want the researchers assessing their kindergarteners. Early identification of children who would likely struggle with reading would have meant several more years of specialized instruction for those children — a resource that many schools could not afford.
Performing an MRI scan of each incoming kindergartener is unrealistic (at best), but low-tech, low-cost interventions offer plenty of potential. Simply by paying close attention to very young students with a family history of dyslexia, or who display signs of struggling with language or reading, parents and early educators can give children access to resources early, before any formal testing — and before years of struggle.
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Nadine Gaab's current research within the Laboratories of Cognitive Neuroscience focuses on auditory and language processing in the human brain and its applications for the development of typical and atypical language and literacy skills.