Beyond the Gender Binarism: The Neural Correlates of Trans Men Investigated in a Functional Connectivity–Resting State fMRI Study

Several studies investigated the specific neural correlates of trans people, highlighting mixed results. This study aimed to investigate the presence of specific functional connectivity in trans men, compared to a homogeneous group of cisgender men and cisgender women. 42 participants (19 trans men, 11 cisgender men, and 12 cisgender women) underwent a resting state fMRI; a blood sample was collected in order to evaluate the hormonal status of testosterone, estradiol, and progesterone. Screening measures were administered for evaluating the intellectual ability and manual preference. Moreover, all participants underwent a neuropsychological evaluation of executive functions, attention, visual-perceptual ability, and verbal fluency. Trans men showed a weaker functional connectivity in the precentral gyrus, subcallosal cortex, paracingulate gyrus, temporal pole, and cingulate gyrus in contrast to cisgender men. Furthermore, trans men showed a worse performance than cisgender men and similar to that of cis women in verbal and visuospatial working-memory. In trans men, functional connectivity of precentral gyrus was positively correlated with blood testosterone and negatively correlated with estradiol and progesterone; the cluster involving the subcallosal cortex showed a positive correlation with testosterone and negative with estradiol, and the functional connectivity from a cluster involving the paracingulate gyrus showed a positive correlation with testosterone. This study sheds light to the importance of overpassing the binary-model, by highlighting the presence of neural pathways that could represent the peculiarity of the neural profile of people with gender dysphoria.