A Functional Magnetic Resonance Imaging Study Of The Male Homosexual Viewing Sexual Stimuli

ObjectiveMany studies of human and animal experiments have identified that differences between male homosexual and heterosexual exist relative to some neural structures.However no such differences exist between male homosexual and female heterosexual.In addition,several neurocognitive investigations have demonstrated that the male homosexual has the female intellective characters.The lastest studies of brain functional imaging have indicated that there are some differences between normal male and female in brain function of sexual arousal .On account of above findings, we explored the brain response of the male homosexual and heterosexual to visual sexual stimuli by fMRI in this study,and investigated whether there is difference in them.MethodsTen healthy male homosexual and ten healthy male heterosexual took part in the study.All subjects viewed three types of sexual stimuli :female homosexual couples engaged in sexual activity,male homosexual couples engaged in sexual activity ,male heterosexual and female heterosexual engaged in sexual activity.Ratings of sexual attractiveness were assessed immediately after each scan.Data were analyzed using SPM2 sofeware.Functional EPI volumes were realigned to the first volume and normalized to a standard template volume.Images were subsequently smoothed with an 8-mm isotropic Gaussian kernel.Voxel values for each contrast yielded a statistical parametric map of the t statistic(SPM{t}),subsequently the extrema definded were labelled by anatomical volumes by the Anatomical Automatic Labeling (AAL) software.For the ROI analysis,we did this for each stimulus condition for the amygdale and the thalamus by the MarsBaR software.ResultsWhen the male homosexual experienced sexual arousal viewing erotic stimuli, bilateral blood oxygen level deprendant(BOLD)signal increased in the frontal,occipital,parietal,cingulated,insular,postcentral,temporal cortices,as well as in the thalamus,the nucleus caudatus,the pallidum, the cerebellum and the cerebellar vermis.Compared with the male heterosexual,activation of the lingual gyrus,the hippocampus and the parahippocampal gyrus were not found in the homosexual.However the phenomenon of the activation of the nucleus caudatus and the pallidum did not happen in the heterosexual experiencing sexual aroual.ConclusionThere are some differences in the activated brain regions associated with sexual aroual between the male homosexual and the heterosexual. The possible reason is that the male homosexual has the different emotional and cognitive processing responsed to the visual erotic stimuli ,compared with the heterosexual.