Assessment of Sexual Orientation Using the Hemodynamic Brain Response to Visual Sexual Stimuli

Abstract

Introduction The assessment of sexual orientation is of importance to the diagnosis and treatment of sex offenders and paraphilic disorders. Phallometry is considered gold standard in objectifying sexual orientation, yet this measurement has been criticized because of its intrusiveness and limited reliability. Aim To evaluate whether the spatial response pattern to sexual stimuli as revealed by a change in blood oxygen level-dependent (BOLD) signal can be used for individual classification of sexual orientation. Methods We used a preexisting functional MRI (fMRI) data set that had been acquired in a nonclinical sample of 12 heterosexual men and 14 homosexual men. During fMRI, participants were briefly exposed to pictures of same-sex and opposite-sex genitals. Data analysis involved four steps: (i) differences in the BOLD response to female and male sexual stimuli were calculated for each subject; (ii) these contrast images were entered into a group analysis to calculate whole-brain difference maps between homosexual and heterosexual participants; (iii) a single expression value was computed for each subject expressing its correspondence to the group result; and (iv) based on these expression values, Fisher’s linear discriminant analysis and the κ-nearest neighbor classification method were used to predict the sexual orientation of each subject. Mean Outcome Measure Sensitivity and specificity of the two classification methods in predicting individual sexual orientation. Results Both classification methods performed well in predicting individual sexual orientation with a mean accuracy of >85% (Fisher’s linear discriminant analysis: 92% sensitivity, 85% specificity; κ-nearest neighbor classification: 88% sensitivity, 92% specificity). Conclusion Despite the small sample size, the functional response patterns of the brain to sexual stimuli contained sufficient information to predict individual sexual orientation with high accuracy. These results suggest that fMRI-based classification methods hold promise for the diagnosis of paraphilic disorders (e.g., pedophilia).

A Quantitative Meta-Analysis on Cue-Induced Male Sexual Arousal

“…In the first analysis including studies on male heterosexuals, we identified the importance of the hypothalamus, thalamus, left amygdala, ACC, left anterior insula, bilateral fusiform gyrus, left precentral gyrus, parietal cortex, and bilateral middle occipital cortex. Because there was considerably less data on sexual cue‐reactivity in women and homosexuals, we restricted our analysis to studies on male heterosexuals (for a study comparing homo‐ and heterosexuals, see [24]). A consistent relationship between brain activation and a physiological marker of sexual arousal was found in the hypothalamus extending into the thalamus, bilateral insula, ACC, left postcentral gyrus, and right middle occipital gyrus in a meta‐analysis on whole brain correlations with penile turgidity.…”

Neural Activation Toward Erotic Stimuli in Homosexual and Heterosexual Males

“…This could be a valuable field for future research. Ponseti and colleagues [55], using specific sexual stimuli, even suggest that fMRI‐based classification methods could be used for the diagnosis of paraphilic disorders.…”

Association of Cerebral Networks in Resting State with Sexual Preference of Homosexual Men: A Study of Regional Homogeneity and Functional Connectivity

“…However, heterosexual men showed activation in the bilateral lingual gyrus, right hippocampus, and right parahippocampal gyrus, areas that were not activated in homosexual men. Although Ponseti and colleagues [15] suggested that sexual orientation could be assessed by hemodynamic brain response to visual sexual stimuli, one study showed no difference in the pattern of activation between homosexual and heterosexual participants who were viewing faces of romantic partners of either the opposite or the same gender [16].…”