Magazine article Science News

Dyslexia Tied to Disrupted Brain Network

Magazine article Science News

Dyslexia Tied to Disrupted Brain Network

Article excerpt

Children and adults who exhibit the reading disability known as dyslexia have a difficult time applying appropriate sounds to the letters that make up written words. A new brain-imaging study indicates that a widespread network of brain regions critical to this ability malfunctions in people with dyslexia.

Further work is needed to determine whether this brain disturbance acts as a "neural signature" for the fundamental problem in dyslexia, say pediatrician Sally E. Shaywitz of Yale University School of Medicine and her colleagues.

"These brain activation patterns now provide us with hard evidence of a disruption in the brain regions responsible for reading-evidence for what has previously been a hidden disability," Shaywitz holds.

The Yale researcher's group recruited 14 male and 15 female dyslexic readers, as well as 16 male and 16 female volunteers with no reading impairments. Participants ranged in age from 16 to 63.

During a series of tasks that tapped into progressively more complex manipulations of letter sounds in words, a functional magnetic resonance imaging scanner measured changes in oxygen use in the participants' brains. Brain cells use more oxygen as they work harder.

Dyslexic readers had the most trouble when asked to identify nonsense words that rhyme, such as "leat" and "jete." Actual words that rhyme, many of which had already been memorized by the dyslexic readers, usually proved less vexing for them.

Compared to unimpaired readers performing these tasks, dyslexic readers lacked neural activity in several regions toward the back of the brain, Shaywitz and her coworkers report in the March 3 Proceedings of the National Academy of Sciences. These include Wernicke's area, which contributes to language comprehension, as well as parts of the visual cortex and a section of the association cortex considered pivotal to integrating the sight of printed letters with their corresponding sounds. …

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