Transsexualism and sex-related differences in hemispheric asymmetry.

Sex differences in human brain lateralization are documented by studies on normal subjects, patients with the unilateral brain damage, and individuals with atypical level of hormones. However, there is no agreement as to the specific role of gender in the development of hemispheric asymmetry. This experiment was designed to examine whether gender identity plays an important role in the formation of brain lateralization, as some recent data seem to suggest. A group of subjects showing gender dysphoria (transsexuals) and two groups of control male and female subjects were presented with verbal and visual-spatial tasks. Results show that neither biological sex nor gender identity are sufficient factors to determine the pattern of hemispheric asymmetry.