Psychotic disorders such as schizophrenia have been associated with both language impairment and decreased hemispheric asymmetry [Crow, 2000]. The association of an additional X chromosome with both of these cognitive features raised the question of whether there may be a dose-response relationship of the X chromosome and cerebral asymmetry. This group further explored this hypothesis by measuring cerebral torque (a combination of rightward frontal and leftward occipital asymmetry) in 10 of these 47,XXY males and matched controls together with data from a group of 45,XO women and female controls [Rezaie et al., 2009]. Cerebral torque was not significantly different in either patient group. However, the 47,XXY males had decreased asymmetry in the frontal lobes compared with male controls, whereas 45,XO women had increased leftward asymmetry compared with matched healthy female controls, suggesting that X chromosome dosage may affect the development of brain asymmetry in ways besides affecting torque.
