Dyslexia, gender, and brain imaging

Future brain imaging studies of dyslexia should have a sufficient number of males and females to detect possible gender differences in the neurologica l underpinning of this disorder. Detailed knowledge about such differences may clarify our understanding of the structural and functional impairments which lead to the phonological deficits that characterize dyslexia. Functional brain imaging studies have shown that males and females exhibit different patterns of brain activation during phonological processing. Furt her differences between the brains of males and females have been suggested by studies of normal brain development, morphology, and functional activat ion during reading. Animal studies have shown that lesions, similar to thos e seen in postmortem studies of dyslexia, affect rapid auditory processing in males, but not in females. The targe body of research on gender differences in brain development, func tional organization, and activation during reading tasks urges separation o f males and females in dyslexia research in order to minimize variance and to detect subtle, but functionally-relevant, differences. Well-controlled s tudies, with large numbers of male and female dyslexics, may produce more s ensitive and accurate identification of the neurological substrates of dysl exia. (C) 1999 Elsevier Science Ltd. All rights reserved.