Abstract
Nowadays the mechanism of homosexuality is little known. Few studies have been carried out to explore the brain functional changes of homosexual men during sexual arousal. We used functional MR imaging (fMRI) to determine whether the patterns of brain activation in homosexual and heterosexual men differed during visually evoked sexual arousal. To all the subjects (10 homosexual and 10 heterosexual), real-time visual stimulation was provided by 3-minute exposure to 3 types of erotic film: heterosexual couples (F-M), male homosexual couples (M-M), and female homosexual couples (F-F) engaged in sexual activity, during which time fMRI was used to determine the patterns of brain activation. Self-reports of level of sexual arousal were collected immediately afterward. Statistical parametric mapping showed that viewing erotic film excerpts that induced sexual arousal was associated, in both groups, with activation of the middle prefrontal gyrus, bilateral temporal lobe and postcentral gyrus, thalamus, insula, vermis, left precuneus, occipital cortex, parietal cortex, and cerebellum. In homosexual men, the left angular gyrus, left caudate nucleus, and right pallidum were activated; in contrast, heterosexual men showed no activation in these regions. However, heterosexual men showed activation in the bilateral lingual gyrus, right hippocampus, and right parahippocampal gyrus, areas not activated in homosexual men. In both groups, region-of-interest analysis revealed no correlation between the magnitude of amygdala or thalamus activation and the reported level of sexual arousal. Our findings indicate that different neural circuits are active during sexual arousal in homosexual and heterosexual men and may contribute to a better understanding of the neural basis of male sexual orientation.
Highlights
AND PURPOSE: Nowadays the mechanism of homosexuality is little known
MATERIALS AND METHODS: To all the subjects (10 homosexual and 10 heterosexual), real-time visual stimulation was provided by 3-minute exposure to 3 types of erotic film: heterosexual couples (F-M), male homosexual couples (M-M), and female homosexual couples (F-F) engaged in sexual activity, during which time functional MR imaging (fMRI) was used to determine the patterns of brain activation
Statistical parametric mapping showed that viewing erotic film excerpts that induced sexual arousal was associated, in both groups, with activation of the middle prefrontal gyrus, bilateral temporal lobe and postcentral gyrus, thalamus, insula, vermis, left precuneus, occipital cortex, parietal cortex, and cerebellum
Summary
To all the subjects (10 homosexual and 10 heterosexual), real-time visual stimulation was provided by 3-minute exposure to 3 types of erotic film: heterosexual couples (F-M), male homosexual couples (M-M), and female homosexual couples (F-F) engaged in sexual activity, during which time fMRI was used to determine the patterns of brain activation. Self-reports of level of sexual arousal were collected immediately afterward. Subjects Subjects were enrolled through advertisements on campus and in a homosexual club asking for participation in a study on central nervous processing of sexual stimuli. Twenty healthy men took part in the study, 10 homosexual (mean age, 26.50 Ϯ 5.10 years) and 10 heterosexual (mean age, 27.90 Ϯ 3.03 years). The sexual orientation of all subjects was assessed by using self-reported measures of sexual feeling (ie, sexual attraction and sexual fantasies). All subjects gave informed consent to participate, and the study was approved by the Zhejiang University Human Investigations Committee. All subjects were told in detail about the aims of the study and what was expected of them in the experiment
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