[Biological foundations of dyslexia. A review]

This is a review that summarizes the work done in our laboratory during the last three years. We have studied four dyslexic brains. They all bear a symmetric anatomical pattern in a structure closely related to the language areas (planum temporale), which is more commonly asymmetric in normal brains. In addition, their microscopic examination shows numerous ectopias and dysplasias in the cerebral cortex. The high incidence of immune disease in dyslexics and their families suggests a more general developmental problem in developmental dyslexia. The hypothesis is raised that fetal effects of testosterone are involved in regulating neurological as well as immunological development, whereby abnormally high testosterone activity would produce a twofold deficit. Finally, strains of immune-defective mice have been found that bear the same cortical abnormalities as seen in the dyslexic brains previously studied. The immune-defective mouse may prove to be an excellent model for the study of the neuropathological basis of developmental dyslexia.