Accurate sex classification from neural responses to sexual stimuli

Sex differences in brain activity evoked by sexual stimuli remain elusive despite robust evidence for stronger enjoyment of and interest towards sexual stimuli in men than in women. To test whether visual sexual stimuli evoke different brain activity patterns in men and women, we measured haemodynamic brain activity induced by visual sexual stimuli in two experiments in 91 subjects (46 males). In one experiment, the subjects viewed sexual and non-sexual film clips and dynamic annotations for nudity in the clips was used to predict their hemodynamic activity. In the second experiment, the subjects viewed sexual and non-sexual pictures in an event-related design. Males showed stronger activation than females in the visual and prefrontal cortices and dorsal attention network in both experiments. Furthermore, using multivariate pattern classification we could accurately predict the sex of the subject on the basis of the brain activity elicited by the sexual stimuli. The classification generalized across the experiments indicating that the sex differences were consistent across the experiments. Eye tracking data obtained from an independent sample of subjects (N = 110) showed that men looked longer than women at the chest area of the nude female actors in the film clips. These results indicate that visual sexual stimuli evoke discernible brain activity patterns in men and women which may reflect stronger attentional engagement with sexual stimuli in men than women.

Asexuality vs. sexual interest/arousal disorder: Examining group differences in initial attention to sexual stimuli

Attention is considered to be a critical part of the sexual response cycle, and researchers have differentiated between the roles of initial (involuntary) and subsequent (voluntary) attention paid to sexual stimuli as part of the facilitation of sexual arousal. Prior studies using eye-tracking methodologies have shown differing initial attention patterns to erotic stimuli between men and women, as well as between individuals of different sexual orientations. No study has directly compared initial attention to sexual stimuli in asexual individuals, defined by their lack of sexual attraction, to women with Sexual Interest/Arousal Disorder (SIAD), a disorder characterized by a reduced or absent interest in sex coupled with significant personal distress. The current study tested differences in the initial attention patterns of 29 asexual individuals (Mage = 26.56, SD = 4.80) and 25 heterosexual women with SIAD (Mage = 27.52, SD = 4.87), using eye-tracking. Participants were presented with sexual and neutral stimuli, and their initial eye movements and initial fixations to both image types and areas of erotic contact within sexual images were recorded. Mixed-model ANOVAs and t-tests were used to compare the two groups on the speed with which their initial fixations occurred, the duration of their initial fixations, and the proportion of initial fixations made to sexual stimuli. On two indices of initial attention, women with SIAD displayed an initial attention preference for sexual stimuli over neutral stimuli compared to asexual participants. This study adds to a growing literature on the distinction between asexuality and SIAD, indicating that differences in early attention may be a feature that differentiates the groups.

Electrophysiological evidence of enhanced early attentional bias toward sexual images in individuals with tendencies toward cybersex addiction

Background and aims Attentional bias is a key factor in addictive behavior maintenance. However, whether attentional bias has a similar effect on cybersex addiction is unclear. We investigated differences in the attentional processing of sexually explicit images between individuals with high tendencies toward cybersex addiction (TCA) versus low tendencies using behavioral and electrophysiological indices. Methods Twenty-eight individuals with high TCA and 29 with low TCA performed an addiction Stroop task comprising sexual and neutral images in colored frames. Participants were asked to respond to the frame color and not the image contents, and behavioral and event-related potentials were recorded. Results Behaviorally, an addiction Stroop interference effect was found in the high TCA group, as shown by the longer reaction times to judge the frame colors of sexual images. Electrophysiologically, a P200 (150–220 ms) enhancement was present in response to sexual images compared with neutral ones, which was absent in the low TCA group. The event-related potential correlates with the addiction Stroop interference effect, indicating that the attentional bias underlying the addiction Stroop interference operates at an automatic level. A general, sexually related bias was found in the late positive potential (300–700 ms) amplitude, although between-group differences were insignificant. Discussion and conclusions These findings indicate that sexual stimuli grab the attentional resources of individuals with high TCA at early automatic stages of attentional processing. Increased cue reactivity to sexual stimuli may contribute to pornographic consumption and play a crucial role in sustaining problematic excessive use of online pornography.

Rapid changes in brain estrogen concentration during male sexual behavior are site and stimulus specific

Classically, estrogens regulate male sexual behavior through effects initiated in the nucleus. However, neuroestrogens, i.e., estrogens locally produced in the brain, can act within minutes via membrane-initiated events. In male quail, rapid changes in brain aromatase activity occur after exposure to sexual stimuli. We report here that local extracellular estrogen concentrations measured by in vivo microdialysis increase during sexual interactions in a brain site- and stimulus-specific manner. Indeed, estrogen concentrations rose within 10 min of the initiation of sexual interaction with a female in the medial preoptic nucleus only, while visual access to a female led to an increase in estrogen concentrations only in the bed nucleus of the stria terminalis. These are the fastest fluctuations in local estrogen concentrations ever observed in the vertebrate brain. Their site and stimulus specificity strongly confirm the neuromodulatory function of neuroestrogens on behavior.

Gender-specific genital and subjective sexual arousal to prepotent sexual stimuli in androphilic men and gynephilic women

Marked differences have been found in men’s and women’s sexual response patterns, contingent upon their sexual orientation; androphilic (attracted to men) and gynephilic (attracted to women) men demonstrate greatest genital and self-reported arousal to their preferred stimulus type (a “gender-specific” response), whereas androphilic women do not, and findings for gynephilic women have been mixed. While there have been many investigations into gynephilic men’s and androphilic women’s (i.e., heterosexual men/women) sexual response, there has been less investigation into the specificity of sexual response of androphilic men and gynephilic women. Given the complex nature of sexual stimuli that are used in sexual response research, it is often unclear to what extent contextual cues (e.g., cues other than the sexual actor’s primary and secondary sex characteristics, such as physical attractiveness, sexual activity, etc.) influence participants’ sexual response patterns. As such, the current study examined genital, discrete self-reported, and continuous self-reported responses of androphilic men ( n = 22) and gynephilic women ( n = 10) to prepotent sexual features (stimuli thought to elicit automatic sexual arousal: erect penises and exposed vulvas), non-prepotent sexual features (flaccid penises and pubic triangles) and neutral stimuli (clothed men and women). Both samples exhibited a gender-specific pattern of genital, self-reported, and continuous self-reported sexual arousal. Similarly, all measures of sexual arousal were generally found to be greatest to “prepotent” sexual cues. Implications for understanding gender specificity of sexual response are discussed.

Focusing the Conceptualization of Erotophilia and Erotophobia on Global Attitudes Toward Sex: Development and Validation of the Sex Positivity-Negativity Scale

Previous measures of erotophobia/erotophilia like the Sexual Opinion Survey (SOS) assessed gut-level positive-negative affective and evaluative reactions to a wide range of sexual stimuli, resulting in purposefully diverse item content. Although an effective strategy, the item content of existing erotophilia/erotophobia scales is now potentially too generalized, encompassing what have since developed as an array of more focused constructs in the current literature like attitudes toward (1) casual sex, (2) pornography, (3) non-heterosexual orientations (e.g., homophobia), and (4) masturbation. The current study therefore sought to evaluate existing scales and to develop a conceptually focused measure of sex-positivity and sex-negativity using a distinct strategy designed to obviate the need for overly generalized (and potentially imbalanced or confounding) item content. Using responses from 2,205 online respondents (82% Caucasian, 66% heterosexual, 50% female) completing an item pool of 158 items, the current study employed a combination of classic test-theory analyses (e.g., exploratory and confirmatory factor analyses) and Item Response Theory (IRT) analyses to develop a psychometrically optimized scale–the Sex Positivity-Negativity (SPN) scale. The SPN scale demonstrated: (1) a stable 2-subscale structure distinguishing sex-negativity from sex-positivity, (2) consistently high levels of internal consistency across 31 demographic subsamples, (3) more discriminant than convergent validity with existing erotophilia scales given its novel focus, (4) discriminant validity with more specific sexual attitudes, (5) greater levels of power and precision for detecting differences between individuals, (6) stronger links to individual, sexual, and relationship functioning than existing scales, and (7) incremental validity over the SOS for predicting change in relationship dynamics over 6 months. The findings therefore suggested that the SPN scale is a conceptually-focused measure of sex-positivity and sex-negativity offering researchers a comparatively short and effective tool. Implications are discussed.

Insular Cortex Response to Static Visual Sexual Stimuli

According to previous research, the insula is important for processing salient and emotional stimuli, but its precise role remains elusive. By combining high spatial and temporal resolution, intracranial electroencephalography (iEEG) might contribute to filling this gap. Four drug-resistant epileptic patients with intracranial electrodes in the insula were instructed to watch and rate pictures with sexual content and neutral pictures. Event-related potentials (ERPs) were computed separately for both types of stimuli. Ninety-three percent of the anterior insula (AI) and 85% of the posterior insula (PI) contacts showed differences between ERPs. AI-positive deflections tended to have an earlier onset than PI-positive deflections. The results suggest that the AI generates a P300-like response and contributes to the early phase of the late positive potential, both components found enhanced while viewing emotional stimuli in the ERP literature. The present findings are interpreted as congruent with the role of the AI in maintaining attention to salient stimuli.

Premature Ejaculation Symptoms Are Associated with Sexual Excitability: Empirical Support for the Hyperarousability Model

Premature ejaculation (PE) is a common sexual complaint among men, but its etiology is poorly understood. Previous studies on the dual control model of sexuality has revealed that propensities for sexual excitation and inhibition can contribute to sexual dysfunctions, but few studies have included a measure of premature ejaculation. We sought to explore whether PE is associated with sexual excitation or inhibition. We applied structural equation models to data from a large population-based sample of Finnish adult men. The analyses supported a four-factor solution for the sexual inhibition/sexual excitation short-form scale. The clearest result was that increased symptoms of PE were associated with a greater propensity for sexual excitation (β = 151, p < 001, n = 2953). Importantly, this excitation was intrapersonal, as opposed to stemming from social activities. The results imply that men with PE may have stronger and more rapid reactions to sexual stimuli, which in turn may lead to ejaculating earlier than desired.