Association of cerebral networks in resting state with sexual preference of homosexual men: a study of regional homogeneity and functional connectivity

Abstract

Recent imaging studies have shown that brain morphology and neural activity during sexual arousal differ between homosexual and heterosexual men. However, functional differences in neural networks at the resting state is unknown. The study is to characterize the association of homosexual preference with measures of regional homogeneity and functional connectivity in the resting state. Participants were 26 healthy homosexual men and 26 age-matched healthy heterosexual men in whom we collected echo planar magnetic resonance imaging data in the resting state. The sexual orientation was evaluated using the Kinsey Scale. We first assessed group differences in regional homogeneity 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 regional homogeneity and functional connectivity were assessed by examining their associations with Kinsey Scores. Homosexual participants showed significantly reduced regional homogeneity in the left inferior occipital gyrus, right middle occipital gyrus, right superior occipital gyrus, left cuneus, right precuneus, and increased regional homogeneity in rectal gyrus, bilateral midbrain, and left temporal lobe. Regional homogeneity correlated positively with Kinsey scores in the left inferior occipital gyrus. The homosexual group also showed reduced functional connectivity between left middle temporal gyrus, left supra-marginal gyrus, right cuneus and the seed region, i.e. left inferior occipital gyrus. Additionly, the connection between the left inferior occipital gyrus and right thalamus correlated positively with Kinsey scores. These differences in regional homogeneity and functional connectivity may contribute to a better understanding of the neural basis of male sexual orientation.

Figure 1. Regional homogeneity (ReHo) in the resting state, shown as maps of Kendall’s coefficient of concordance (KCC) within the homosexual group (A) and heterosexual group (B) (one-sample t-test; p<0.05, with multiple correction).

T-sore bars are shown on the right. Hot and cold colors indicate higher or lower than the global mean, respectively.

Figure 2. Results of ReHo shown as a comparison of KCC maps between homosexual and heterosexual groups in the resting state (two-sample t-test; p<0.05, corrected).

T-score bars are shown on the right. Hot and cold colors indicate increased and decreased ReHo in homosexual group, respectively, compared with heterosexual group. The identified brain regions are the following: (A&B) right precuneus; (C) right superior occipital gyrus; (D) left cuneus; (E) left temporal lobe; (F) right middle occipital gyrus; (G) right extra-nuclear white matter; (H) left inferior occipital; (I) right midbrain; (J) left midbrain; (K) left rectal gyrus.

Figure 3. Significant correlations of ReHo in the resting state with in the homosexual group with Kinsey Scale scores (correlation analysis, p<0.05, corrected).

R-value are shown on the right. Hot and cold colors indicate the positive and negative correlations, respectively. The identified brain regions are the following: (A) left Cerebelum; (B) left inferior occipital gyrus; the cluster circled was selected as seed for FC analysis; (C) left precentral cortex; (D) left supplementary motor area; (E) right postcentral cortex.

Figure 4. The identified brain region is seed region where ReHo correlated significantly with the Kinsey scale for sexual preference and also is one of the regions where ReHo differed between the homosexual and the heterosexual groups.

The seed region has 145 voxels. P<0.05, corrected.

Figure 5. Functional connectivity in the resting state, shown as correlation maps of time series with the seed region in the homosexual group (A) and heterosexual group (B) (one-sample t-test; p<0.05, with multiple correction).

T-sore bars are shown on the right. Hot and cold colors indicate higher or lower than the global mean, respectively.

Figure 6. Differences in functional connectivity (differences in r-value maps) in the resting state between homosexual and heterosexual groups (two-sample t-test; p<0.05, corrected).

T-score bars are shown on the right. Hot and cold colors indicate increased and decreased FC of homosexual group, respectively, compared with heterosexual group. The identified brain regions are the following: (A) left inferior occipital gyrus; (B) left middle temporal gyrus; (C) right cuneus; (D) left supramarginal gyrus.

Figure 7. Significant correlations of FC in the resting state with Kinsey Scale scores within the homosexual group (correlation analysis, p<0.01, corrected).

R-value are shown on the right. The identified region is right thalamus (A) and right cuneus (B).