Dyslexia and Comprehension

Dsylexia isn't limited to the written word. Brain scans reveal that the part of the brain responsible for speech recognition is inactive in children with this disorder.

By Colin Allen, published on October 29, 2003 - last reviewed on June 30, 2005

Dyslexia isn’t limited to the written word. Children with this disorder also respond differently to speech, finds a brain scan study from the University of Texas in Houston. When hearing spoken words, dyslexic children do not use the area of the brain traditionally responsible for speech recognition. This change apparently makes it difficult for them to distinguish similar sounds.

Study coauthor Joshua Breier, a professor in the department of neurosurgery, measured the brain activity of dyslexic and non-dyslexic children as they distinguished syllables that sound alike such as 'ga' and 'ka'. Normal children showed activity in the left lobe, specifically in the temporoparietal areas found on the surface of the back of the brain. This area is known to control phonological processing, which is key to developing reading skills.

Dyslexic kids did not have the same spike of activity in the left lobe, but a corresponding area in the right hemisphere peaked at relatively higher levels. Researchers don't know what this area of the brain does. Breier suggests that the right lobe may be attempting to compensate for the left lobe's inaction.

"Children with dyslexia are well known to have problems with phonological processing tasks," says Breier. "The area [in the brain] that is down while they read is also down when they do a simple phoneme description."

Dyslexic children can be taught to use the inactive area of the left lobe. In previous studies, Breier found that after language training, cognitive activity in the left lobe increases. In future research, he plans to investigate if lessons learned from dyslexia can be applied to stroke victims.

The study was published in the journal Neuropsychology.