LOUISVILLE, Ky. –Differences in brain structure may explain the challenges and unique talents of people with autism, reports Dr. Manuel Casanova, a neuroscientist in the University of Louisville Department of Psychiatry. According to a study released today in the Journal of Autism and Developmental Disorders, this work is now yielding insights into dyslexia, a learning disability that causes difficulty with reading and written language.
“These two conditions stand on the opposite ends of a spectrum,” Casanova explained. “The common link is a bias in terms of brain connectivity.”
Casanova and his colleagues have mapped the way tiny strands of brain tissue – called cortical cell minicolumns – develop and connect in normal people and in people with autism, dyslexia and other language problems.
Their previous studies suggest that people with autism spectrum disorders may excel at mathematics and visual discrimination because their brains are structured to make short, local connections between minicolumns. However, they can have trouble speaking and recognizing faces because their brains lack the structure to make integrated connections over longer distances to minicolumns in other regions of the brain.
This study demonstrates that people with dyslexia show an opposite pattern of connectivity that favors longer connections at the expense of shorter ones, as measured by the spaces between cell minicolumns. This pattern of connectivity may yield a greater capacity for abstract, “visionary” thinking.
People with dyslexia also have longer fibers in parts of the brain involved in language processing. The researchers believe this leads to differences in the way their brains develop early in life and that their brains don’t adapt as efficiently to the process of learning to read. These adaptations have been shown in studies of early brain development in children without any learning disabilities.
“In short, dyslexic brains are structured so that they are more likely to develop a less efficient reading circuit,” Casanova said. “This explains why children with dyslexia have difficulty sounding out words despite normal or superior cognitive skills.”