Anatomy and Genetics In 1979 anatomical differences in the brain of a young dyslexic were documented by Galaburda at Harvard Medical School when he noticed that language centers in dyslexic brains showed microscopic flaws known as ectopias and microgyria. An ectopia (or 'brain wart') is a collection of neurons that have pushed up from lower cortical layers into the outermost one. A microgyrus is an area of cortex that includes only four layers instead of six. These flaws affect connectivity and functionality of the cortex in critical areas related to sound and visual processing. Now it also thought that dyslexics have: Symmetrical planum temporale (in normals this is larger in the left hemisphere); Thinner axons in left hemisphere; Smaller visual magnocells; and less activity in visual motion areas, left angular gyrus, Wernicke's and Broca's areas when reading.

Dyslexia is an inherited condition: a gene on the short arm of chromosome 6 may be responsible for dyslexia. That gene is dominant, making dyslexia highly heritable.

Some people with dyslexia appear to have larger brain right-hemispheres than normal readers. This may be one reason people with dyslexia often have significant strengths in areas controlled by the right-side of the brain, such as artistic, athletic, and mechanical gifts; 3-D visualization ability; musical talent; creative problem solving skills; and intuitive people skills.