Cross-sex hormone treatment and own-body perception: behavioral and brain connectivity profiles

Behzad S Khorashad,Amirhossein Manzouri,Jamie D Feusner,Ivanka Savic

doi:10.1038/s41598-020-80687-2

Behzad S Khorashad, Amirhossein Manzouri + Show 2 more

Open Access

https://doi.org/10.1038/s41598-020-80687-2

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Abstract

Referrals for gender dysphoria (GD), characterized by a distressful incongruence between gender identity and at-birth assigned sex, are steadily increasing. The underlying neurobiology, and the mechanisms of the often-beneficial cross-sex hormone treatment are unknown. Here, we test hypothesis that own body perception networks (incorporated in the default mode network—DMN, and partly in the salience network—SN), are different in trans-compared with cis-gender persons. We also investigate whether these networks change with cross-sex hormone treatment. Forty transmen (TrM) and 25 transwomen (TrW) were scanned before and after cross-sex hormone institution. We used our own developed Body Morph test (BM), to assess the perception of own body as self. Fifteen cisgender persons were controls. Within and between-group differences in functional connectivity were calculated using independent components analysis within the DMN, SN, and motor network (a control network). Pretreatment, TrM and TrW scored lower “self” on the BM test than controls. Their functional connections were weaker in the anterior cingulate-, mesial prefrontal-cortex (mPFC), precuneus, the left angular gyrus, and superior parietal cortex of the DMN, and ACC in the SN “Self” identification and connectivity in the mPFC in both TrM and TrW increased from scan 1 to 2, and at scan 2 no group differences remained. The neurobiological underpinnings of GD seem subserved by cerebral structures composing major parts of the DMN.

Highlights

Referrals for gender dysphoria (GD), characterized by a distressful incongruence between gender identity and at-birth assigned sex, are steadily increasing
These results raise several new questions: (1) are functional connections within the default mode network (DMN) affected among TrW to TrM? (2) are these circuits targeted by cross-sex hormone treatment among transgender populations in general? (3) given that cross-sex hormone treatment is reportedly beneficial—improving congruence between gender identity and own-body, and reducing dysphoria, are the effects of this treatment related to possible changes in own-body processing as measured with the Body Morph (BM) test [for a description of the Body Morph test (BM) test, s ee28]
We hypothesized that the neurobiology of GD is linked to cerebral networks encompassing selfreferential and body ownership regions, primarily with the DMN

Summary

Introduction

Referrals for gender dysphoria (GD), characterized by a distressful incongruence between gender identity and at-birth assigned sex, are steadily increasing. Several research groups, using partly different methodologies, have reported that self-referential processing is mediated by a specific network in the brain encompassing portions of the occipito-parietal (the extra-striatal body area [EBA], the fusiform body area [FBA], the temporoparietal junction [TPJ]), the mesial prefrontal cortex [mPFC], and the anterior cingulate cortex [ ACC]30–32 This network largely overlaps with the default mode network (DMN), (the mPFC, precuneus, bilateral parietal cortices), which is known to be active during rest and when letting the mind wander[33,34,35]. Functional connections within the ventromedial PFC and pACC of the DMN were weaker among TrM compared to cisgender c ontrols[25,28] Together, these data confirm that own-body processing circuits incorporated in the DMN and the salience network are involved in GD. We assumed that tentative between-scan changes in functional connectivity changes would be associated with the altered degree of own body—self-perception (as measured by the 0% morph ratings)

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