Possible Neurobiological Underpinnings of Homosexuality and Gender Dysphoria

Abstract

Although frequently discussed in terms of sex dimorphism, the neurobiology of sexual orientation and identity is unknown. We report multimodal magnetic resonance imaging data, including cortical thickness (Cth), subcortical volumes, and resting state functional magnetic resonance imaging, from 27 transgender women (TrW), 40 transgender men (TrM), and 80 heterosexual (40 men) and 60 homosexual cisgender controls (30 men). These data show that whereas homosexuality is linked to cerebral sex dimorphism, gender dysphoria primarily involves cerebral networks mediating self-body perception. Among the homosexual cisgender controls, weaker sex dimorphism was found in white matter connections and a partly reversed sex dimorphism in Cth. Similar patterns were detected in transgender persons compared with heterosexual cisgender controls, but the significant clusters disappeared when adding homosexual controls, and correcting for sexual orientation. Instead, both TrW and TrM displayed singular features, showing greater Cth as well as weaker structural and functional connections in the anterior cingulate-precuneus and right occipito-parietal cortex, regions known to process own body perception in the context of self.

Biological sex classification with structural MRI data shows increased misclassification in transgender women

“…This result fits with previous longitudinal studies that have shown reductions of cortical thickness in TW pre to post CHT [16]. Structural and functional alterations of the insula have consistently been associated with transgender compared to CG individuals [45,28,29,10,13]. The insula is associated with body and self-perception.…”

Neuroanatomy of transgender persons in a Non‐Western population and improving reliability in clinical neuroimaging

“…Of note, sexual orientation may also contribute to prior discrepancy. Guillamon et al (2016) and Savic and colleagues (Manzouri & Savic, 2019) hypothesized that sexual orientation may significantly contribute to the discrepant findings as it was not well-controlled for in previous work (e.g., Luders et al, 2009;Mueller, Landre, et al, 2017) or, instead, the sample size was very small (Simon et al, 2013). One strength of the present study was that both trans- The second objective aimed to examine how divergence in anatomical findings can be further reduced, especially when dealing with populations with small prevalence rates.…”

Fluidity of gender identity induced by illusory body-sex change

“…The present findings demonstrate that a change in the appearance of one's own body can sufficiently perturb the sense of own gender. 13 A thorough reader might ask: if the perception of one's own body is so critical for gender identity, then how can these two aspects remain in conflict for a prolonged period of time in transgender individuals? First, our results should not be treated as evidence that the perceived bodily sex is the only factor that shapes the sense of own gender; instead, this sense is a complex phenomenon that is constructed from multiple factors1,2,5-7.…”