Male sexual orientation, gender nonconformity, and neural activity during mental rotations: an fMRI study

Functional lateralization in social-emotional processing: The influence of sexual orientation and gender identity on cradling preferences

The left-cradling bias (i.e., the motor asymmetry for cradling infants on the left side) has often been associated to the right-hemispheric social-emotional specialization, and it has often been reported to be stronger in females than in males. In this study we explored the effects of sexual orientation and gender identity on this lateral bias by means of a web-based investigation in a sample of adults (485 biological females and 196 biological males) recruited through LGBTQIA+ networks and general university forums. We exploited a cradling imagery task to assess participants' cradling-side preference, and standardized questionnaires to assess participants' homosexuality (Klein Sexual Orientation Grid) and gender nonconformity (Gender Identity/Gender Dysphoria Questionnaire for Adults and Adolescents). Results confirmed the expected left-cradling bias across all sexual orientation groups except for heterosexual males. Importantly, higher homosexuality scores were associated with higher proportions of left cradling in males. These results suggest that sexual orientation can influence cradling preference in males, indicating a complex interaction between biological and psychological factors in the laterality of social-emotional processing. Finally, the left-cradling bias seems to confirm its role as a behavioral proxy of social-emotional functional lateralization in humans.

Giftedness and atypical sexual differentiation: enhanced perceptual functioning through estrogen deficiency instead of androgen excess

Syndromic autism spectrum conditions (ASC), such as Klinefelter syndrome, also manifest hypogonadism. Compared to the popular Extreme Male Brain theory, the Enhanced Perceptual Functioning model explains the connection between ASC, savant traits, and giftedness more seamlessly, and their co-emergence with atypical sexual differentiation. Overexcitability of primary sensory inputs generates a relative enhancement of local to global processing of stimuli, hindering the abstraction of communication signals, in contrast to the extraordinary local information processing skills in some individuals. Weaker inhibitory function through gamma-aminobutyric acid type A (GABAA) receptors and the atypicality of synapse formation lead to this difference, and the formation of unique neural circuits that process external information. Additionally, deficiency in monitoring inner sensory information leads to alexithymia (inability to distinguish one's own emotions), which can be caused by hypoactivity of estrogen and oxytocin in the interoceptive neural circuits, comprising the anterior insular and cingulate gyri. These areas are also part of the Salience Network, which switches between the Central Executive Network for external tasks and the Default Mode Network for self-referential mind wandering. Exploring the possibility that estrogen deficiency since early development interrupts GABA shift, causing sensory processing atypicality, it helps to evaluate the co-occurrence of ASC with attention deficit hyperactivity disorder, dyslexia, and schizophrenia based on phenotypic and physiological bases. It also provides clues for understanding the common underpinnings of these neurodevelopmental disorders and gifted populations.

Early Female Transgender Identity after Prenatal Exposure to Diethylstilbestrol: Report from a French National Diethylstilbestrol (DES) Cohort

Diagnostic of transsexualism and gender incongruence are terms to describe individuals whose self-identity does not match their sex assignment at birth. A transgender woman is an individual assigned male at birth (AMAB) on the basis of the external or internal genitalia who identifies and lives as a woman. In recent decades, a significant increase in the number of transgender people has been reported. Although, its etiology is unknown, biological, anatomical, genetic, environmental and cultural factors have been suggested to contribute to gender variation. In XY animals, it has been shown that environmental endocrine disruptors, through their anti-androgenic activity, induce a female identity. In this work, we described four XY individuals who were exposed in utero to the xenoestrogen diethylstilbesterol (DES) and were part of the French HHORAGES cohort. They all reported a female transgender identity starting from childhood and adolescence. This high prevalence of male to female transgenderism (1.58%) in our cohort of 253 DES sons suggests that exposure to chemicals with xenoestrogen activity during fetal life may affect the male sex identity and behavior.

Sex and gender correlates of sexually polymorphic cognition

BACKGROUND

Sexually polymorphic cognition (SPC) results from the interaction between biological (birth-assigned sex (BAS), sex hormones) and socio-cultural (gender identity, gender roles, sexual orientation) factors. The literature remains quite mixed regarding the magnitude of the effects of these variables. This project used a battery of classic cognitive tests designed to assess the influence of sex hormones on cognitive performance. At the same time, we aimed to assess the inter-related and respective effects that BAS, sex hormones, and gender-related factors have on SPC.

METHODS

We recruited 222 adults who completed eight cognitive tasks that assessed a variety of cognitive domains during a 150-min session. Subgroups were separated based on gender identity and sexual orientation and recruited as follows: cisgender heterosexual men (n = 46), cisgender non-heterosexual men (n = 36), cisgender heterosexual women (n = 36), cisgender non-heterosexual women (n = 38), gender diverse (n = 66). Saliva samples were collected before, during, and after the test to assess testosterone, estradiol, progesterone, cortisol, and dehydroepiandrosterone. Psychosocial variables were derived from self-report questionnaires.

RESULTS

Cognitive performance reflects sex and gender differences that are partially consistent with the literature. Interestingly, biological factors seem to better explain differences in male-typed cognitive tasks (i.e., spatial), while psychosocial factors seem to better explain differences in female-typed cognitive tasks (i.e., verbal).

CONCLUSION

Our results establish a better comprehension of SPC over and above the effects of BAS as a binary variable. We highlight the importance of treating sex as a biological factor and gender as a socio-cultural factor together since they collectively influence SPC.

Associations between recalled childhood gender nonconformity and adult sexual dysfunction in Denmark: baseline assessment in the Project SEXUS cohort study

BACKGROUND

Sexual dysfunctions may negatively affect an individual's self-perceived womanhood or manhood, but whether gender nonconformity in childhood or adolescence can influence adult sexual functioning has not been examined so far.

AIM

To explore the possible link between recalled childhood gender nonconformity and sexual dysfunctions in adulthood in a large sample.

METHODS

We analyzed baseline questionnaire data from Project SEXUS, a nationally representative cohort study on sexual health among 15- to 89-year-old Danish citizens. Our sample included sexually active participants aged ≥18 years who were queried about gender nonconformity in childhood or adolescence (N = 21 390). To capture sexual dysfunctions, we assessed (1) difficulties with lubrication, orgasm, vaginal cramps precluding sexual intercourse, and/or genital pain during partnered sexual activity in women and (2) difficulties with erection, premature ejaculation, orgasm, and/or genital pain during partnered sexual activity in men. Furthermore, we assessed whether such difficulties were perceived as problematic. The 6-item Female Sexual Function Index and the 5-item International Index of Erectile Function served as standardized measures. Polytomous logistic regression analyses yielded demographically weighted adjusted odds ratios (aORs) with 95% CIs for associations between childhood gender nonconformity and sexual dysfunctions, controlling for age, sociodemographics, health-related factors, and other potential confounders.

OUTCOMES

Sexual difficulties and dysfunctions, as well as scores on the Female Sexual Function Index and International Index of Erectile Function.

RESULTS

Age-adjusted odds ratios indicated that sexual dysfunctions were significantly more common among childhood gender-nonconforming than conforming participants. After controlling for additional potential confounders, most sexual dysfunctions-notably, vaginal cramps in women (aOR, 2.12; 95% CI, 1.25-3.60) and genital pain dysfunction in men (aOR, 2.99; 95% CI, 1.79-4.99)-remained significantly increased among childhood gender-nonconforming respondents.

CLINICAL IMPLICATIONS

Findings suggest that self-perceived gender nonconformity in childhood or adolescence may negatively affect sexual functioning in adult life. If confirmed by future studies, they may warrant a clinical emphasis on such issues in sexologic treatment and care.

STRENGTHS AND LIMITATIONS

Our study is the first to report associations between childhood gender nonconformity and adult sexual dysfunction, building on data from a large-scale, nationally representative cohort study. The retrospective assessment of childhood gender nonconformity via one item might have neglected significant dimensions of this construct.

CONCLUSION

The present study is the first to show that individuals who recall being gender nonconforming in childhood or adolescence may be at a greater risk of experiencing sexual dysfunctions, particularly sexual pain disorders, as adults.

Carving the Biodevelopment of Same-Sex Sexual Orientation at Its Joints

Sexual orientation is a core aspect of human experience and understanding its development is fundamental to psychology as a scientific discipline. Biological perspectives have played an important role in uncovering the processes that contribute to sexual orientation development. Research in this field has relied on a variety of populations, including community, clinical, and cross-cultural samples, and has commonly focused on female gynephilia (i.e., female sexual attraction to adult females) and male androphilia (i.e., male sexual attraction to adult males). Genetic, hormonal, and immunological processes all appear to influence sexual orientation. Consistent with biological perspectives, there are sexual orientation differences in brain development and evidence indicates that similar biological influences apply across cultures. An outstanding question in the field is whether the hypothesized biological influences are all part of the same process or represent different developmental pathways leading to same-sex sexual orientation. Some studies indicate that same-sex sexually oriented people can be divided into subgroups who likely experienced different biological influences. Consideration of gender expression in addition to sexual orientation might help delineate such subgroups. Thus, future research on the possible existence of such subgroups could prove to be valuable for uncovering the biological development of sexual orientation. Recommendations for such future research are discussed.

Effects of gender nonconformity and biological sex on the relationship between sexual orientation microaggressions and anxiety and depressive symptoms among lesbian, gay, and bisexual Taiwanese young adults: A moderated-moderation study

BACKGROUND

Sexual orientation microaggressions (SOMs) may negatively affect lesbian, gay, and bisexual (LGB) individuals' mental health. However, the moderating effects of gender nonconformity and biological sex on the relationship between SOMs and anxiety and depressive symptoms has never been examined. We evaluated the moderating effect of gender nonconformity on the association of SOMs with anxiety and depressive symptoms among LGB young male and female adults. We hypothesized that the associations of SOMs with anxiety and depressive symptoms weakened with increasing gender nonconformity among gay and bisexual men but strengthened with increasing gender nonconformity among lesbian and bisexual women.

METHODS

In total, 1000 self-identified LGB young adult individuals participated in the study. The experience of sexual orientation microaggression was assessed using the Sexual Orientation Microaggression Inventory, anxiety was assessed using the State subscale on the State-Trait Anxiety Inventory, and depression was assessed using the Center for Epidemiological Studies-Depression Scale. The two-way moderation models stratified by sex examined the moderating effects of gender nonconformity on the association between SOMs and anxiety symptoms in the male and female participants. The three-way moderated moderation models were used to determine whether gender nonconformity and sex jointly moderated the associations between SOMs and anxiety and depressive symptoms.

RESULTS

In the two-way moderation models stratified by sex, gender nonconformity exerted opposite moderating effects on the association between SOMs and anxiety and depressive symptoms in the male and female participants. For the male participants, the association between SOMs and anxiety (β = -0.08) and depressive symptoms (β = -0.09) weakened with increasing gender nonconformity. For the female participants, the association between SOMs and anxiety (β = 0.08) and depressive symptoms (β = 0.13) strengthened with increasing gender nonconformity. The three-way moderated moderation models further confirmed that sex moderated the moderating effects of gender nonconformity on the associations between SOM and anxiety (β = -0.16, p = .047) and depressive symptoms (β = -0.22, p < .001).

LIMITATION

The cross-sectional study design limited the inferences that could be made concerning the temporal relationship between SOMs and mental health problems.

CONCLUSIONS

The association between SOMs and anxiety and depressive symptoms weakened with increasing gender nonconformity in gay and bisexual men, whereas the association between SOMs and anxiety and depressive symptoms strengthened with increasing gender nonconformity in lesbian and bisexual women.

Imaging the Spin: Disentangling the Core Processes Underlying Mental Rotation by Network Mapping of Data From Meta-analysis

Research on the mental rotation task has sparked debate regarding the specific processes that underly the capability of humans to mentally rotate objects. The spread of reported brain activations suggests that mental rotation is subserved by a neural network circle. However, no common network has yet been found that uncovers the crucial processes underlying this ability. We aimed to identify the common network crucial for mental rotation by coordinate-based network mapping of previous neuroimaging findings in mental rotation. A meta-analysis revealed 710 peak activation coordinates from 42 fMRI studies in mental rotation, which include a total 844 participants. The coordinates were mapped to a normative functional connectome (n = 1000) to identify a network of connected regions. To account for experimental factors, we examined this network against two control tasks, action imitation and symbolic number processing. A common and crucial network for mental rotation, centring on dorsal premotor, superior parietal and inferior temporal lobes was revealed. This network, separated from other experimental aspects, suggests that the crucial processes underlying mental rotation are motor rotation, visuospatial processing, and higher order visual object recognition.

Accurate machine learning prediction of sexual orientation based on brain morphology and intrinsic functional connectivity

BACKGROUND

Sexual orientation in humans represents a multilevel construct that is grounded in both neurobiological and environmental factors.

OBJECTIVE

Here, we bring to bear a machine learning approach to predict sexual orientation from gray matter volumes (GMVs) or resting-state functional connectivity (RSFC) in a cohort of 45 heterosexual and 41 homosexual participants.

METHODS

In both brain assessments, we used penalized logistic regression models and nonparametric permutation.

RESULTS

We found an average accuracy of 62% (±6.72) for predicting sexual orientation based on GMV and an average predictive accuracy of 92% (±9.89) using RSFC. Regions in the precentral gyrus, precuneus and the prefrontal cortex were significantly informative for distinguishing heterosexual from homosexual participants in both the GMV and RSFC settings.

CONCLUSIONS

These results indicate that, aside from self-reports, RSFC offers neurobiological information valuable for highly accurate prediction of sexual orientation. We demonstrate for the first time that sexual orientation is reflected in specific patterns of RSFC, which enable personalized, brain-based predictions of this highly complex human trait. While these results are preliminary, our neurobiologically based prediction framework illustrates the great value and potential of RSFC for revealing biologically meaningful and generalizable predictive patterns in the human brain.

Medial Prefrontal Cortex Activity to Reward Outcome Moderates the Association Between Victimization Due to Sexual Orientation and Depression in Youth

BACKGROUND

Sexual minority youth (SMY) are 3 times more likely to experience depression than heterosexual peers. Minority stress theory posits that this association is explained by sexual orientation victimization, which acts as a stressor to impact depression. For those vulnerable to the effects of stress, victimization may worsen depression by altering activity in neural reward systems. This study examines whether neural reward systems moderate the influence of sexual orientation victimization, a common and distressing experience in SMY, on depression.

METHODS

A total of 81 participants ages 15 to 22 years (41% SMY, 52% marginalized race) reported sexual orientation victimization, depression severity, and anhedonia severity, and underwent a monetary reward functional magnetic resonance imaging task. Significant activation to reward > neutral outcome (p_{familywise error} < .05) was determined within a meta-analytically derived Neurosynth reward mask. A univariate linear model examined the impact of reward activation and identity on victimization-depression relationships.

RESULTS

SMY reported higher depression (p < .001), anhedonia (p = .03), and orientation victimization (p < .001) than heterosexual youth. The bilateral ventral striatum, medial prefrontal cortex (mPFC), anterior cingulate cortex, and right orbitofrontal cortex were significantly active to reward. mPFC activation moderated associations between sexual orientation victimization and depression (p = .03), with higher depression severity observed in those with a combination of higher mPFC activation and greater orientation victimization.

CONCLUSIONS

Sexual orientation victimization was related to depression but only in the context of higher mPFC activation, a pattern observed in depressed youth. These novel results provide evidence for neural reward sensitivity as a vulnerability factor for depression in SMY, suggesting mechanisms for disparities, and are a first step toward a clinical neuroscience understanding of minority stress in SMY.

To What Extent are Prenatal Androgens Involved in the Development of Male Homosexuality in Humans?

Endocrine variations, including possibly reduced exposure to androgens, may contribute to the development of male homosexuality, with animal models demonstrating same-sex mate preference with altered exposure during prenatal or early postnatal development. As similar studies in humans are impossible, indirect physical and cognitive measures of androgen exposure are used. Some studies suggest that physical measures affected by prenatal androgens, including the index-to-ring finger ratio, growth indices, and facial structure, are more "feminine" in gay men. Gay men also exhibit significant childhood gender non-conformity and a "feminized" anatomical and functional brain pattern in sexual arousal, as well as domains such as language, visuospatial skills and hemispheric relationships. However, many of these results are equivocal and may be confounded by other factors. Research has also been hampered by inconsistencies in the reporting of sexual orientation and the potentially unrepresentative populations of gay men studied, while additional complexities pertaining to gender conformity and sexual role may also influence results.

Childhood Gender Nonconformity and Recalled Perceived Parental and Peer Acceptance Thereof, Internalized Homophobia, and Psychological Well-Being Outcomes in Heterosexual and Gay Men from Poland

The link between gender nonconformity and psychopathology may be due in part to negative childhood experiences resulting from other people's reactions to gender nonconformity. The aim of this study was to test whether recalled perceived levels of parental and peer acceptance of childhood gender nonconforming behaviors and play mediate the relationship of childhood gender nonconformity with depression and social anxiety in adulthood. We also tested whether this relationship was moderated by sexual orientation and, among gay men, whether internalized homophobia was an additional mediator. All variables were measured in a large sample of male participants using self-report (n = 449 gay men, age: M = 27.8 years, SD = 6.69; and n = 296 heterosexual men, age: M = 27.4 years, SD = 6.57) in Poland. Gay men reported more childhood gender nonconformity than heterosexual men. The relationship between gender nonconformity and depressive symptoms as well as social anxiety symptoms was significant in both gay and heterosexual men. Among gay men, this relationship was partially mediated by peer but not parental acceptance of the measured aspects of gender nonconformity and internalized homophobia. Among heterosexual men, recalled perceived parental acceptance of gender nonconformity partially mediated the relationship between gender nonconformity and depressive and social anxiety symptoms. Our findings were partially in line with those found in Western European and North American samples. Although the two groups differed in their recalled perceived gender nonconformity, they did not differ in their depression or social anxiety scores. Nevertheless, childhood gender nonconformity may be an indirect risk associated with mental health symptoms, irrespective of sexual orientation. Its higher prevalence among nonheterosexual individuals makes it a particular risk for this group.

A systematic review of the neural correlates of sexual minority stress: towards an intersectional minority mosaic framework with implications for a future research agenda

BACKGROUND

Systemic oppression, particularly towards sexual minorities, continues to be deeply rooted in the bedrock of many societies globally. Experiences with minority stressors (e.g. discrimination, hate-crimes, internalized homonegativity, rejection sensitivity, and microaggressions or everyday indignities) have been consistently linked to adverse mental health outcomes. Elucidating the neural adaptations associated with minority stress exposure will be critical for furthering our understanding of how sexual minorities become disproportionately affected by mental health burdens.

Following PRISMA-guidelines, we systematically reviewed published neuroimaging studies that compared neural dynamics among sexual minority and heterosexual populations, aggregating information pertaining to any measurement of minority stress and relevant clinical phenomena.

RESULTS

Only 1 of 13 studies eligible for inclusion examined minority stress directly, where all other studies focused on investigating the neurobiological basis of sexual orientation. In our narrative synthesis, we highlight important themes that suggest minority stress exposure may be associated with decreased activation and functional connectivity within the default-mode network (related to the sense-of-self and social cognition), and summarize preliminary evidence related to aberrant neural dynamics within the salience network (involved in threat detection and fear processing) and the central executive network (involved in executive functioning and emotion regulation). Importantly, this parallels neural adaptations commonly observed among individuals with posttraumatic stress disorder (PTSD) in the aftermath of trauma and supports the inclusion of insidious forms of trauma related to minority stress within models of PTSD.

CONCLUSIONS

Taken together, minority stress may have several shared neuropsychological pathways with PTSD and stress-related disorders. Here, we outline a detailed research agenda that provides an overview of literature linking sexual minority stress to PTSD and insidious trauma, moral affect (including shame and guilt), and mental health risk/resiliency, in addition to racial, ethnic, and gender related minority stress. Finally, we propose a novel minority mosaic framework designed to inform future directions of minority stress neuroimaging research from an intersectional lens.

Mental rotation task performance in relation to sexual and gender diversity in Thailand

Neurohormonal theory argues that organizational effects of hormone exposure influence sexual orientation and gender identity, as well as sex differences in visuospatial cognition. This study examined mental rotation task (MRT) performance in a diverse Thai sample (N = 980). Thai culture has several third genders: individuals assigned male at birth (AMAB) who are feminine and attracted to cis men (i.e., sao praphet song); individuals assigned female at birth (AFAB) who are masculine and attracted to feminine individuals (i.e., toms); AFAB individuals who are feminine and attracted to toms (i.e., dees); and sexual orientation categories similar to Western culture (e.g., gay, lesbian, bi). On the MRT, straight cis men outperformed straight cis women. Results were consistent with organizational effects among AMAB individuals, with straight cis men outperforming gay cis men and sao praphet song. Among AFAB individuals, however, only bi and lesbian cis women outperformed dees. Overall, support for neurohormonal theory was limited among AFAB individuals, but MRT performance among AMAB individuals was consistent with organizational effects. This study informs our understanding of visuospatial sex/gender differences and the applicability of neurohormonal theory across cultures.

Structural, Functional, and Metabolic Brain Differences as a Function of Gender Identity or Sexual Orientation: A Systematic Review of the Human Neuroimaging Literature

This review systematically explored structural, functional, and metabolic features of the cisgender brain compared with the transgender brain before hormonal treatment and the heterosexual brain compared to the homosexual brain from the analysis of the neuroimaging literature up to 2018, and identified and discussed subsequent studies published up to March 2021. Our main aim was to help identifying neuroradiological brain features that have been related to human sexuality to contribute to the understanding of the biological elements involved in gender identity and sexual orientation. We analyzed 39 studies on gender identity and 24 on sexual orientation. Our results suggest that some neuroanatomical, neurophysiological, and neurometabolic features in transgender individuals resemble those of their experienced gender despite the majority resembling those from their natal sex. In homosexual individuals the majority resemble those of their same-sex heterosexual population rather than their opposite-sex heterosexual population. However, it is always difficult to interpret findings with noninvasive neuroimaging. Given the gross nature of these measures, it is possible that more differences too subtle to measure with available tools yet contributing to gender identity and sexual orientation could be found. Conflicting results contributed to the difficulty of identifying specific brain features which consistently differ between cisgender and transgender or between heterosexual and homosexual groups. The small number of studies, the small-to-moderate sample size of each study, and the heterogeneity of the investigations made it impossible to meta-analyze all the data extracted. Further studies are necessary to increase the understanding of the neurological substrates of human sexuality.