Dyslexia is a prevalent learning disorder where genetics frequently play a significant role. How do the genes tied to dyslexia connect with brain structure in the general population? In a comprehensive research study published in Science Advances, scientists from the Max Planck Institute for Psycholinguistics in Nijmegen discovered that genetic variations linked to a higher likelihood of dyslexia correspond to variations in brain regions related to motor coordination, vision, and language.
Dyslexia is a prevalent learning disorder where genetics frequently play a significant role. How do the genes tied to dyslexia connect with brain structure in the general population? In a comprehensive research study published in Science Advances, scientists from the Max Planck Institute for Psycholinguistics in Nijmegen discovered that genetic variations linked to a higher likelihood of dyslexia correspond to variations in brain regions related to motor coordination, vision, and language.
Approximately 5% of children in school struggle significantly with reading and/or spelling, a condition referred to as dyslexia. “Dyslexia is partially shaped by genetics and is quite heritable,” states the lead author, Sourena Soheili-Nezhad. “However, it is a complicated trait that cannot be fully explained by alterations in a single brain area or a single gene. By examining which genes influence which brain networks, we can better understand how cognitive functions are differently developed in this learning difficulty.”
Genetic Risk for Dyslexia
To explore the connection between the genetics of dyslexia and brain structure, Soheili-Nezhad and his team conducted a large genetic study. They utilized data from over a million individuals gathered by the company 23andMe, identifying numerous genetic variants that elevate the odds of a person experiencing dyslexia.
For over 30,000 adults from a vast database (the UK Biobank), the researchers calculated ‘polygenic scores’ for dyslexia and correlated those with brain images. Although the UK Biobank database did not include specific information on who had dyslexia, the genetic predisposition to dyslexia varied among adults and could still be linked to specific brain regions.
Internal Capsule
A higher genetic predisposition for dyslexia was related to reduced volume in brain areas that govern motor coordination and speech sound processing. In contrast, the genetic variants associated with dyslexia showed increased volume in the visual cortex.
The researchers also identified variations in a white matter tract situated deep within the brain, known as the internal capsule. In this region, the density of white matter was linked to genetic factors influencing not only dyslexia but also educational achievement, fluid intelligence, and attention deficit/hyperactivity disorder (ADHD), conditions associated with dyslexia.
Brain Development
“These findings align with the notion that dyslexia is a complex trait potentially involving various altered cognitive mechanisms,” remarks Clyde Francks, the study’s senior author. “Even though our research utilized data from adults, some brain changes likely stem from the altered development of the brain during early life, like during fetal stages or infancy, which remain consistent throughout a person’s life. Other changes may indicate the brain’s adaptation over years of altered behaviors in individuals with a stronger genetic predisposition to dyslexia. For instance, a lifetime of steering clear of reading both personally and professionally might affect the brain’s visual processing system.”
Cause or Consequence?
In upcoming research, the team intends to analyze data from children or teenagers instead of adults to gain deeper insights into which brain changes contribute to causing dyslexia, rather than being effects of possessing the condition.
“Gaining a deeper understanding of the brain’s role in dyslexia could potentially lead to earlier identification and tailored educational interventions in the future, with strategies specifically designed to meet the individual needs of children,” concludes Soheili-Nezhad.
