Genetics of Dyslexia: Part 1

Genetics of Dyslexia: Part 1

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While there is no one “dyslexia gene,” genetics do play a role when a child develops dyslexia. It’s important to note that genetics is just one part of dyslexia; a number of other factors also underlie the propensity towards dyslexia. For today’s purposes, however, we will consider some recent discoveries pointing to the heritability of dyslexia.

In a collaboration between Children’s Hospital Boston Department of Cognitive Neuroscience and Developmental Medicine and Harvard Medical School, researchers explored the heritability of dyslexia by looking for changes in white matter in the brains of infants. While previous studies point to measurable white matter differences in the left side of the brain in dyslexic kindergarten students, these scientists wanted to determine if these changes could be seen in much younger children. Specifically, they were looking for changes to the part of the brain known as the arcuate fasciculus.

What exactly is the arcuate fasciculus? It’s a substantial bundle of axons (nerve cells) that connects three areas of the brain: the temporal cortex, the inferior parietal cortex, and certain locations in the frontal lobe. One of the key roles of the arcuate fasciculus is connecting Broca’s and Wernicke’s areas, which are involved in producing and understanding language.

A three-dimensional rendering of the brain, highlighting the location of the arcuate fasciculus and showing how it connects Broca's territory, wernicke's territory, and Geschwind's territory, all vital to how the brain processes language. The genetics of dyslexia are connected to diminished functioning in the arcuate fasciculus. Studying the genetics of dyslexia can help children receive an earlier diagnosis and the help they need.
Image courtesy of Marco Catani et al. ‘Frontal networks in adults with autism spectrum disorder’ Brain Feb 2016, 139 (2) 616-630; DOI: 10.1093/brain/awv351

To that end, they assembled fourteen infants with a family history of dyslexia, aged six to eighteen months, and eighteen infants with no family history of dyslexia, between the ages of five and seventeen months. Then the researchers used diffusion MRI to measure the ability of the arcuate fasciculus to transmit information in each infant’s brain. What did the scientists discover?

Fully 50 percent of the infants with a sibling or parent with dyslexia showed measurable diminishment in their left arcuate fasciculus. Additionally, the central portions of the arcuate fasciculus showed significantly lower levels of ability to transmit information when compared to infants with no family history of dyslexia.

Interestingly, the infants with the most robust arcuate fasciculus—namely, those with no family history of dyslexia—demonstrated the most expressive language skills. The conclusion of the study states, “Our results demonstrate that atypical brain development associated with Developmental Dyslexia is already present within the first 18 months of life, suggesting that the deficits associated with Developmental Dyslexia may result from altered structural connectivity in left-hemispheric regions.”

My hope is that one day soon, all infants can benefit from early screening to diagnose dyslexia well before the child enters school. This data will offer parents the opportunity to better prepare their children for success by building a solid preliteracy foundation.

The study this blog is based upon:

For a thorough discussion of dyslexia, you may enjoy the second edition of my award-winning book Raising a Child with Dyslexia: What Every Parent Needs to Know, available in softcover, hardcover, eBook, and audio. In addition to facts on testing and accommodation, my book gives you the tools to provide the social and emotional support children with dyslexia require. The second edition has the same great content as the first edition but now contains a very helpful bibliography and index and an exciting new cover.

Cover of Raising a Child with Dyslexia: What Every Parent Needs to Know by Don M. Winn. Cover shows the silhouetted heads of a parent and child facing each other. Instead the brain area of each silhouette is an outline of a maze. The two mazes are connected by a white line leading to the center of the brain maze of the parent and child.

You may also enjoy Failing Students or Failing Schools? A Parent’s Guide to Reading Instruction and Intervention, by reading specialist and shortlisted World Literacy Award nominee Faith Borkowsky.

Cover of the book Failing Students or Failing Schools? A Parent's Guide to Reading Instruction and Intervention by Faith Borkowsky. Cover depicts a large stack of books and a boy sitting on the floor, hiding his face in his arms with a despondent attitude.

Cardboard Box Adventures picture books are great for shared reading and can help parents establish a strong preliteracy foundation for their children. Check out the CBA Catalog for a full list of award-winning picture books, chapter books, and resources for parents and educators. Visit my Amazon author page for more information.