Specific Cerebral Activation due to Visual Erotic Stimuli in Male-to-Female Transsexuals Compared with Male and Female Controls: An fMRI Study
ABSTRACT Transsexuals harbor the strong feeling of having been born to the wrong sex. There is a continuing controversial discussion of whether or not transsexualism has a biological representation. Differences between males and females in terms of functional imaging during erotic stimuli have been previously described, revealing gender-specific results.
Therefore, we postulated that male-to-female (MTF) transsexuals may show specific cerebral activation differing from their biological gender.
Cerebral activation patterns during viewing of erotic film excerpts in functional magnetic resonance imaging (fMRI).
Twelve male and 12 female heterosexual volunteers and 12 MTF transsexuals before any treatment viewed erotic film excerpts during fMRI. Additionally, subjective rating of sexual arousal was assessed. Statistics were performed using the Statistical Parametric Mapping software.
Significantly enhanced activation for men compared with women was revealed in brain areas involved in erotic processing, i.e., the thalamus, the amygdala, and the orbitofrontal and insular cortex, whereas no specific activation for women was found. When comparing MTF transsexuals with male volunteers, activation patterns similar to female volunteers being compared with male volunteers were revealed. Sexual arousal was assessed using standard rating scales and did not differ significantly for the three groups.
We revealed a cerebral activation pattern in MTF transsexuals compared with male controls similar to female controls compared with male controls during viewing of erotic stimuli, indicating a tendency of female-like cerebral processing in transsexualism.
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ABSTRACT: Adolescents with gender dysphoria (GD) may be treated with gonadotropin releasing hormone analogs (GnRHa) to suppress puberty and, thus, the development of (unwanted) secondary sex characteristics. Since adolescence marks an important period for the development of executive functioning (EF), we determined whether the performance on the Tower of London task (ToL), a commonly used EF task, was altered in adolescents with GD when treated with GnRHa. Furthermore, since GD has been proposed to result from an atypical sexual differentiation of the brain, we determined whether untreated adolescents with GD showed sex-atypical brain activations during ToL performance. We found no significant effect of GnRHa on ToL performance scores (reaction times and accuracy) when comparing GnRHa treated male-to-females (suppressed MFs, n=8) with untreated MFs (n=10) or when comparing GnRHa treated female-to-males (suppressed FMs, n=12) with untreated FMs (n=10). However, the suppressed MFs had significantly lower accuracy scores than the control groups and the untreated FMs. Region-of-interest (ROI) analyses showed significantly greater activation in control boys (n=21) than control girls (n=24) during high task load ToL items in the bilateral precuneus and a trend (p<0.1) for greater activation in the right DLPFC. In contrast, untreated adolescents with GD did not show significant sex differences in task load-related activation and had intermediate activation levels compared to the two control groups. GnRHa treated adolescents with GD showed sex differences in neural activation similar to their natal sex control groups. Furthermore, activation in the other ROIs (left DLPFC and bilateral RLPFC) was also significantly greater in GnRHa treated MFs compared to GnRHa treated FMs. These findings suggest that (1) GnRHa treatment had no effect on ToL performance in adolescents with GD, and (2) pubertal hormones may induce sex-atypical brain activations during EF in adolescents with GD. Copyright © 2015 Elsevier Ltd. All rights reserved.Psychoneuroendocrinology 03/2015; 56. DOI:10.1016/j.psyneuen.2015.03.007 · 5.59 Impact Factor
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ABSTRACT: Numerous studies have attempted to isolate biological factors in the development of transgender identities through research into genetics, prenatal hormone exposure, neuroanatomy, and cognitive processing. Genetic studies demonstrate that chromosomal variations are uncommon but may occur at higher rates than in the general population. Candidate genes have been investigated, with some positive results, though these have yet to be replicated. Investigations into the effects of hormone exposure on the developing fetus have focused on gender identity in intersex people, which is often unpredictable, and proxy markers for prenatal hormone exposure such as finger length ratio and birth order, which do not show clear trends in transgender groups. A few small neuroanatomical studies show distinctions in transgender people, but results are limited in their scope due to small sample sizes and confounding variables such as adult hormone exposure. Numerous studies demonstrate that male-to-female (MTF) transgender people have higher rates of left-handedness, but the theoretical basis for this difference is not well described. Accumulating evidence indicates that prenatal biology likely contributes to transgender identity, but that its role may be interactive, rather than deterministic.Journal of Gay & Lesbian Mental Health 04/2013; 17(2):150-174. DOI:10.1080/19359705.2013.753393
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ABSTRACT: Die Suche nach den neurobiologischen Grundlagen sexueller und transsexueller Entwicklungen beschäftigt die Wissenschaft seit mehr als fünf Jahrzehnten. Das Wissen um die Sexualdifferenzierung neuronaler Strukturen konnte seitdem erheblich erweitert werden. Die vorliegende Arbeit stellt exemplarisch genetische, neuroendokrinologische, neurostrukturelle und neurofunktionelle Befunde vor, die in einem Zusammenhang mit transsexuellen Entwicklungen stehen können. In der Zusammenschau liefern die dargestellten Forschungsergebnisse Hinweise dafür, dass es neurobiologische Muster zu geben scheint, die einen Einfluss auf geschlechtsatypische Verhaltensweisen haben und in Interaktion mit psychologischen und sozialen Einflüssen die Wahrscheinlichkeit für eine transsexuelle Entwicklung erhöhen. Das Verständnis um die Bedingungen transsexueller Entwicklungen wird durch dieses zunehmende neurobiologische Wissen maßgeblich erweitert. Eine offene und multidisziplinäre Diskussion ist notwendig, um die neurobiologischen Befunde sinnvoll in die Theorie und Praxis transsexueller Entwicklungen zu integrieren.Zeitschrift für Sexualforschung 10/2011; 24(3):199-227. DOI:10.1055/s-0031-1283716 · 0.33 Impact Factor