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

<b>Introduction</b>: Several studies have investigated the specific neural correlates of trans people, highlighting mixed results. This study aimed to compare the presence of specific functional connectivity and differences in cognitive profile and hormone levels in trans men diagnosed with gender dysphoria (GD), and a homogeneous group of cisgender men and cisgender women. <b>Methods</b>: A total of 42 participants (19 trans men, 11 cisgender men, and 12 cisgender women) underwent a resting state fMRI and were measured for blood levels of testosterone, estradiol, and progesterone. A neuropsychological battery evaluated executive functions, attention, visual-perceptual ability, verbal fluency, manual preference, and general intelligence. <b>Results</b>: Trans men showed weaker functional connectivity in the precentral gyrus, subcallosal cortex, paracingulate gyrus, temporal pole, and cingulate gyrus than cisgender men (<i>p</i> < 0.01). Trans men performed worse than cisgender men in verbal and visuospatial working memory but similarly to cisgender women (<i>p</i> < 0.05). In trans men, functional connectivity of the precentral gyrus correlated positively with testosterone (<i>r</i> = 0.459, <i>p</i> = 0.064) and negatively with estradiol (<i>r</i> = -0.654, <i>p</i> = 0.004) and progesterone blood levels (<i>r</i> = -0.475, <i>p</i> = 0.054). The cluster involving the subcallosal cortex showed a positive correlation with testosterone (r = 0.718, <i>p</i> = 0.001), and a negative correlation with estradiol (r = -0.602, <i>p</i> = 0.011). The functional connectivity from a cluster involving the paracingulate gyrus showed a positive correlation with testosterone (<i>r</i> = 0.592, <i>p</i> = 0.012). <b>Conclusions</b>: This study highlights the importance of overpassing the binary model by underlining the presence of neural pathways that could represent the peculiarity of the neural profile of people with GD.