Antonio Guillamon‘s team at the National University of Distance Education in Madrid, Spain, think they have found a better way to spot a transsexual brain. In a study due to be published next month, the team ran MRI scans on the brains of 18 female-to-male transsexual people who’d had no treatment and compared them with those of 24 males and 19 females.
They found significant differences between male and female brains in four regions of white matter – and the female-to-male transsexual people had white matter in these regions that resembled a male brain (Journal of Psychiatric Research, DOI: 10.1016/j.jpsychires.2010.05.006). “It’s the first time it has been shown that the brains of female-to-male transsexual people are masculinised,” Guillamon says.
In a separate study, the team used the same technique to compare white matter in 18 male-to-female transsexual people with that in 19 males and 19 females. Surprisingly, in each transsexual person’s brain the structure of the white matter in the four regions was halfway between that of the males and females (Journal of Psychiatric Research, DOI: 10.1016/j.jpsychires.2010.11.007). “Their brains are not completely masculinised and not completely feminised, but they still feel female,” says Guillamon.