Gender incongruence and the brain - Behavioral and neural correlates of voice gender perception in transgender people.

The phenomenon of gender incongruence is hypothesized to arise from a discrepant sexual development of the brain and the genitals, contingent on genetic and hormonal mechanisms. We aimed at visualizing transgender identity on a neurobiological level, assuming a higher functional similarity to individuals of the aspired rather than assigned sex. Implementing a gender perception paradigm featuring male and female voice stimuli, behavioral and functional imaging data of transmen were compared to men and women, and to transwomen, respectively. Men had decreased activation in response to voices of the other sex in regions across the frontoparietal and insular cortex, while the activation patterns of women and transmen were characterized by little or no differentiation between male and female voices. Further, transmen had a comparatively high discrimination performance for ambiguous male voices, possibly reflecting a high sensitivity for voices of the aspired sex. Comparing transmen and transwomen yielded only few differences in the processing of male compared to female voices. In the insula, we observed a pattern similar to that of men and women, the neural responses of the transgender group being in accordance with their gender identity rather than assigned sex. Notwithstanding the similarities found dependent on biological sex, the findings support the hypothesis of gender incongruence being a condition in which neural processing modes are partly incongruent with one's assigned sex.