A MRI Study Of Cerebral Structure And Function In Resting State Of Homosexual Men

Objective:The mechanism of homosexulity is not clear. Recent imaging studies have shown that neural activities during sexual arousal differ between homosexual and heterosexual men. Whether task-related functional differences also exist in the resting state is unknown. And little studies of gray matter of homosexual men had been made. The study is to characterize the association of homosexual preference with measures of regional homogeneity, fractional amplitude of low-frequency fluctuation and functional connectivity, and to compare the difference in volumes of gray matter between two groups.Methods:Participants were30healthy homosexual men and26healthy heterosexual men in whom we collected echo planar magnetic resonance imaging (MRI) data in the resting state and three-dimensional spoiled gradient MRI data. The sexual orientation was evaluated using the Kinsey Scale. We first assessed group differences in regional homogeneity (ReHo) and franctional amplitude of low-frequency fluctuation (fALFF), and then, taking the identified differences as seed regions, we compared groups in measures of functional connectivity from those seeds. The behavioral significances of the differences in ReHo, fALFF and functional connectivity were assessed by examining their associations with Kinsey Scale scores. And voxel-based morphometry was used to compare the volume of gray matter between homosexual and heterosexual men.Results:Homosexual participants showed significantly reduced ReHo in the left inferior occipital gyrus, right middle occipital gyrus, right superior occipital gyrus, left cuneus, right precuneus, and increased ReHo in the rectal gyrus, bilateral midbrain, and left temporal lobe. Regional homogeneity correlated positively with Kinsey Scale scores in the left inferior occipital gyrus. The functional connection between left inferior occipital gyrus and right thalamus correlated positively with Kinsey Scale scores. On the other hand, homosexual men in resting state showed significantly increased fALFF in right middle frontal gyrus, right anterior cerebellum lobe, and decreased fALFF in left postcentral gyrus, left lingual gyrus, right pallidum, right postcentral gyrus, left inferior parietal gyrus, right superior temporal gyrus, left cuneus, left inferior frontal gyrus. Homosexual group showed significant positive correlation in left postcentral gyrus and left cuneus with the Kinsey Scale scores. There was significantly positive correlation between Kinsey scale scores and functional connection in left superior parietal gyrus connected with left cuneus (r=0.575, p<0.01). Voxel-based Morphometry analysis showed that homosexual group had increased volume of gray matter in bilaterial frontal gyrus, right hippocampus, left middle occipital gyrus, right supramarginal gyrus, left middle frontal gyrus, and decreased volume of gray matter in left inferior frontal gyrus, right postcentral gyrus, compared to heterosexual group. There was significantly negative correlation between Kinsey Scale scores and the volume of gray matter in right postcentral gyrus (r=-0.37, p<0.05), and positive correlation between Kinsey Scale scores and the volume of gray matter in left amygdala at a trend-level of significance for homosexual participants (r=0.31, p<0.1).Conclusion:The are significant differences in ReHo, fALFF and functional connectivity between homosexual and heterosexual men in resting state. Additionally, homosexual men have significantly difference in volume of gray matter compared with heterosexual men. These cerebral structural and functional characteristics may contribute to a better understanding of the neural basis of male sexual orientation.