 Research into potential genetic causes of dyslexia has its roots in post @-@ autopsy examination of the brains of people with dyslexia . Observed anatomical differences in the language centers of such brains include microscopic cortical malformations known as <unk> , more rarely , vascular micro @-@ malformations , and <unk> . The previously cited studies and others suggest that abnormal cortical development presumed to occur before or during the sixth month of fetal brain development was the cause of the abnormalities . Abnormal cell formations in dyslexics have also been reported in non @-@ language cerebral and subcortical brain structures . Several genes have been associated with dyslexia , including <unk> and <unk> on chromosome 6 , and <unk> on chromosome 15 . 
