Dyslexia: Cultural diversity and biological unity

The recognition of dyslexia as a neurodevelopmental disorder has been hampe red by the belief that it is not a specific diagnostic entity because it ha s variable and culture-specific manifestations. In line with this belief, w e found that Italian dyslexics, using a shallow orthography which facilitat es reading, performed better on reading tasks than did English and French d yslexics, However, all dyslexics were equally impaired relative to their co ntrols on reading and phonological tasks. Positron emission tomography scan s during explicit and implicit reading showed the same reduced activity in a region of the Left hemisphere in dyslexics from all three countries, with the maximum peak in the middle temporal gyrus and additional peaks in the inferior and superior temporal gyri and middle occipital gyrus. We conclude that there is a universal neurocognitive basis for dyslexia and that diffe rences in reading performance among dyslexics of different countries are du e to different orthographies.