Study finds genetic regional reductions of gray matter may be underlying cause of dyslexia

Researchers in Italy have observed significant reductions of gray matter volume in areas of the brain associated with language processing among people with a family history of dyslexia in comparison with controls with no reading problems. Published in the August 24 issue of Neurology, the scientific journal of the American Academy of Neurology, the study also lends support to previous studies suggesting intensive reading therapy activates areas of the brain necessary for word de-coding.

The study of 10 people with familial dyslexia and 11 controls was the first to employ an advanced testing method – voxel-based morphometry (VBM) – which allows more in-depth detection and measurement of gray-white tissue volume and density differences than other testing tools, including magnetic resonance imaging, or MRI. The brain is made up of gray matter, where the brain cells reside, and white matter, where the nerve tracts that allow connections between different parts of the brain and spinal cord reside. The study also was the first to account for variabilities in whole brain volume, age of the subjects and differences in brain shape.

Each of the subjects with dyslexia had at least one close relative with either clinically evident dyslexia or a long history of reading problems.

Statistically significant gray matter abnormalities were located in many parts of the brain that are important for language functions: the planum temporale, inferior temporale cortex, cerebellar nuclei, the left superior and inferior temporal gyrus, and the right middle temporal gyrus.

“Previous studies employing MRI have suggested that intensive remedial training results in the activation of the posterior portion of the left superior temporal gyrus, which is necessary for the decoding of written language,” said study author Daniela Perani, MD, of Vita-Salute San Raffaele University, Milan, Italy. “Our research showing reduced gray matter volume, including this region of the brain, adds further support to the effectiveness of intensive reading remediation therapy to correct the reading problems associated with dyslexia.”

The study was supported by the Associazione Italiana Dislessia and by the Connectivity in Language Rehabilitation project sponsored by the Vth European Program.

The American Academy of Neurology, an association of more than 18,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as Parkinson’s disease, ALS (Lou Gehrig’s disease), dementia, West Nile virus, and ataxia.