Neural Correlates of Sexual Orientation in Heterosexual, Bisexual, and Homosexual Men

Adam Safron,Martin Walter,Victoria Klimaj,A M Rosenthal,David Sylva,J Michael Bailey,Meng Li

doi:10.1038/srep41314

Adam Safron, Martin Walter + Show 5 more

Open Access

https://doi.org/10.1038/srep41314

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Abstract

Studies of subjective and genital sexual arousal in monosexual (i.e. heterosexual and homosexual) men have repeatedly found that erotic stimuli depicting men’s preferred sex produce strong responses, whereas erotic stimuli depicting the other sex produce much weaker responses. Inconsistent results have previously been obtained in bisexual men, who have sometimes demonstrated distinctly bisexual responses, but other times demonstrated patterns more similar to those observed in monosexual men. We used fMRI to investigate neural correlates of responses to erotic pictures and videos in heterosexual, bisexual, and homosexual men, ages 25–50. Sixty participants were included in video analyses, and 62 were included in picture analyses. We focused on the ventral striatum (VS), due to its association with incentive motivation. Patterns were consistent with sexual orientation, with heterosexual and homosexual men showing female-favoring and male-favoring responses, respectively. Bisexual men tended to show less differentiation between male and female stimuli. Consistent patterns were observed in the whole brain, including the VS, and also in additional regions such as occipitotemporal, anterior cingulate, and orbitofrontal cortices. This study extends previous findings of gender-specific neural responses in monosexual men, and provides initial evidence for distinct brain activity patterns in bisexual men.

Highlights

The term sexual orientation is used to indicate an individual’s sexual arousal and attraction patterns, sexual behavior patterns, or sexual identity[1], which often go together but can differ from each other[2,3,4,5,6]
We focused on the ventral striatum (VS) because it likely has higher validity for reflecting reward compared with the hypothalamus, which contains a variety of nuclei with heterogeneous functions that would be difficult to disambiguate with the limited spatial resolution of 3 T fMRI
First we examined how well VS activity predicts sexual orientation in monosexual men via differential responding to male versus female erotic stimuli within our paradigm

Summary

Introduction

The term sexual orientation is used to indicate an individual’s sexual arousal and attraction patterns, sexual behavior patterns, or sexual identity[1], which often go together but can differ from each other[2,3,4,5,6]. If the term sexual orientation is used to describe a pattern of arousal and attraction[1], genital assessment has high face validity for studying sexual orientation in men. Even with briefly-presented erotic pictures, fMRI has demonstrated a high degree of sensitivity and specificity in measuring sexual orientation[11,12,13]. Specific results vary by experimental paradigm, but findings generally suggest that mechanisms underlying the response to erotic stimuli overlap with those involved in responding www.nature.com/scientificreports/. This is unsurprising, since to the extent that individuals are oriented to seek out particular sexual interactions[19], they are probably— not necessarily5—motivated by the anticipation that such interactions will be rewarding[20,21,22]

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