Science/Tech

Dyslexia Sex Differences: Female Brains Are Wired Differently

Dyslexia Female Sex Differences - Dyslexic Women Brain Anatomy
Dyslexic women have distinct brain differences from men with the reading disability, according to a new neuroimaging study. Creative Commons

In the first study to directly compare the brain anatomy of women with and without dyslexia, Georgetown neuroscientists have found marked differences in the brain anatomy of dyslexic men and women, and girls and boys, compared to their counterparts without the reading disability.

The results, published in the journal Brain Structure and Function, suggest that existing male-based brain models of dyslexia may not apply to dyslexic females.

Dyslexia is at least twice as common among males as it is among females, and as a result previous neuroanatomy studies have focused heavily on dyslexic males.

"It has been assumed that results of studies conducted in men are generalizable to both sexes," said senior author Dr. Guinevere Eden, director of the Center for the Study of Learning at the Georgetown University Medical Center, in a news release.

The findings suggest that dyslexia may have different neural origins in each sex, says Eden, and raises the possibility that girls and boys may benefit from differential diagnosis and treatment.

The Georgetown researchers conducted a magnetic resonance imaging (MRI) study of sex differences among dyslexic and non-dyslexic brains, recruiting 118 adult and child participants from North Carolina and the Washington, DC, metropolitan area.

The adult cohort was split into 27 dyslexic and 27 non-dyslexic participants, with 14 men and 13 women in each group. The children's cohort included 32 dyslexic students and 32 non-dyslexic students who were 9 to 10 years old, with 15 boys and 17 girls in each group.

The MRI brain scans revealed key differences among the groups.

Among males, the results were consistent with previous studies: dyslexics had less gray matter volume in brain areas like the left temporal gyrus, which is involved in language, than their non-dyslexic counterparts.

Among females, dyslexics had less gray matter volume in areas like the right parietal lobe, which is involved in sensory and motor processing. The researchers were surprised to find that, unlike males, there were no differences in the temporal lobe of dyslexic females.

It's well established that male and female brains tend to display distinct anatomical sex differences in the way certain functions are localized, and lead author Dr. Tanya Evans explains that female sex hormones like estrogen are likely to lead to sex-specific brain structures early in development.

"There is sex-specific variance in brain anatomy and females tend to use both hemispheres for language tasks, while males just the left," she said in the press statement.

According to the National Center for Learning Disabilities, up to 15 percent of Americans have reading difficulties like dyslexia. People are born with the reading disability, but appropriate training can help them learn to overcome it.

Understanding the developmental brain processes behind dyslexia can help people of both sexes, say the researchers.

The study only looks at basic sex differences in brain anatomy, and the researchers write that future studies on sex differences in dyslexia need to examine brain function in order to get a more complete picture of how the reading disability develops.

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