Brain Anatomy Of Dyslexia Differs Between The Sexes

Dyslexia defines an anomalous approach to processing information. It is considered a learning disability that impairs a person’s reading comprehension. Dyslexia can manifest as a difficulty with phonological awareness and decoding, language skills, and verbal comprehension.

Dyslexia is the most common learning disability, affecting up to 80 percent of all individuals identified as learning disabled. Individual cases of dyslexia are best explained or defined by the specific underlying neuropsychological deficits and co-occurring learning disabilities such as attention-deficit hyperactivity disorder (ADHD).

Although it is considered to be a language-based learning disability, dyslexia also affects one’s expressive language skills. In contrast, dyslexia can increase the capacity to think multi-dimensionally and help further utilize the brain’s ability to alter and create perceptions.

There are three cognitive subtypes of dyslexia – auditory (dysphonetic), visual (dyseidetic), and attentional.

Auditory dyslexics may have an issue with connecting sounds to the corresponding symbols and letters.

A visual dyslexic usually reverses letters and numbers, due to a difficulty with recognizing and remembering how words, letters, and even numbers look. The most common examples of reversals would be “b” and “d” and “3” and “8.”

Attentional dyslexia is when letters migrate between neighboring words but are correctly identified and keep their correct relative position within the word. For example, fig tree can be read as fig free or even tie free.

Neuroscientists at Georgetown University Medical Center have found notable differences in the brain anatomy when they compared MRIs of men and women with dyslexia. This finding, published in the online journal Brain Structure and Function, suggests the learning disorder may have a different neural manifestation by gender.

Because the condition is more prevalent in males, female have been vastly overlooked in this model of research, according to the senior author, Guinevere Eden, PhD, director for the Center for the Study of Learning and past-president of the International Dyslexia Association.

Researchers compared the brain structures of 118 participants – made up of men, women, boys, and girls. 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.

Dyslexic males, when compared to non-dyslexic counterparts, were found to have less gray matter volume in specific areas like the left temporal gyrus, which is involved in language. In the females, less gray matter volume was found in dyslexics in areas like the right parietal lobe, involved in sensory and motor processing. There were no differences in the temporal lobe of dyslexic females.

Lead author, Tanya Evans, PhD, addressed the importance of studying the differences between the genders as, “There is sex-specific variance in brain anatomy and females tend to use both hemispheres for language tasks, while males just the left. It is also known that sex hormones are related to brain anatomy and that female sex hormones such as estrogen can be protective after brain injury, suggesting another avenue that might lead to the sex-specific findings reported in this study.”

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