A sex difference in features that elicit genital response

Previous research suggests that women's genital arousal is an automatic response to sexual stimuli, whereas men's genital arousal is dependent upon stimulus features specific to their sexual interests. In this study, we tested the hypothesis that a nonhuman sexual stimulus would elicit a genital response in women but not in men. Eighteen heterosexual women and 18 heterosexual men viewed seven sexual film stimuli, six human films and one nonhuman primate film, while measurements of genital and subjective sexual arousal were recorded. Women showed small increases in genital arousal to the nonhuman stimulus and large increases in genital arousal to both human male and female stimuli. Men did not show any genital arousal to the nonhuman stimulus and demonstrated a category-specific pattern of arousal to the human stimuli that corresponded to their stated sexual orientation. These results suggest that stimulus features necessary to evoke genital arousal are much less specific in women than in men.     

Examining gender specificity of sexual response with concurrent thermography and plethysmography

Men's genital responses are significantly greater to sexual stimuli of their preferred gender compared to their nonpreferred gender (gender‐specific), whereas androphilic (i.e., sexually attracted to men) women's genital responses are similar to sexual stimuli depicting either women or men (gender‐nonspecific). This gendered pattern of genital response has only been demonstrated using vaginal photoplethysmography (VPP) in women and primarily penile plethysmography (PPG) in men. These measures assess different aspects of genital vasocongestion, thereby limiting comparisons between genders. Thermography is a newer sexual psychophysiology methodology that measures genital vasocongestion via temperature change and is better suited to assess sexual response between genders because the dependent measure, change in genital temperature, is similar for women and men. Further, previous studies have assessed gender specificity of sexual response across relatively short sexual stimuli, allowing only the examination of initial phases of sexual response. We examined gender specificity of sexual arousal by measuring women's and men's genital responses to lengthier stimuli with concurrent thermography and VPP/PPG. Gynephilic men (i.e., sexually attracted to women; n = 27) and androphilic women (n = 28) viewed 10‐min films depicting men masturbating, women masturbating, and a nonsexual film, and reported feelings of sexual arousal while genital responses were assessed. Across measures, men's sexual responses were gender‐specific and women's responses were gender‐nonspecific, indicating that the gender difference in gender specificity of arousal is robust to methodology and stimulus duration. These findings replicate previous research, extend knowledge of gendered sexual response, and highlight the utility of multimethod approaches in sexual psychophysiology.     

Sexual orientation-related differences in prepulse inhibition of the human startle response

Prepulse inhibition (PPI) refers to a reduction in the startle response to a strong sensory stimulus when this stimulus is preceded by a weaker stimulus--the prepulse. PPI reflects a nonlearned sensorimotor gating mechanism and also shows a robust gender difference, with women exhibiting lower PPI than men. The present study examined the eyeblink startle responses to acoustic stimuli of 59 healthy heterosexual and homosexual men and women. Homosexual women showed significantly masculinized PPI compared with heterosexual women, whereas no difference was observed in PPI between homosexual and heterosexual men. These data provide the first evidence for within-gender differences in basic sensorimotor gating mechanisms and implicate the known neural substrates of PPI in human sexual orientation.     

Gender, sexuality, body image and eating behaviours

One hundred and twenty one participants reported sexual orientation, body mass index, body shape concerns, eating motives and eating styles. Measures of body dissatisfaction were greater in heterosexual women and homosexual men (ps <.05), while heterosexual women had smaller (ps <.001) ideal body shapes. Eating weight control motive was lower in heterosexual men compared to women (ps <.05). Restrained eating was lower in heterosexual men compared to heterosexual women or homosexual men (ps <.001). The findings support the role of socially prescribed body shapes on body shape concerns, eating motivations, and eating styles in men and women and suggest impacts are greater for heterosexual women and homosexual men.     

Racial disparities in sexual risk behaviors and drug use among older gay/bisexual and heterosexual men living with HIV/AIDS

Adults over age 50 comprise 11% of yearly AIDS cases, yet little is known about their sexual risk behaviors and drug use following diagnosis with HIV/AIDS. The present questionnaire study examines potential racial differences in sexual risk and drug use behaviors among 59 HIV-infected gay/bisexual and heterosexual men over age 50 who were recruited from HIV-related organizations in New York City between 1996-1998. The majority (59%) of older men reported unprotected sex since diagnosis, and 36% had done so in the past six months. African-American gay/bisexual men (n=12) were significantly more likely than white gay/bisexual men (n=32) to report unprotected vaginal/anal sex in the past six months (67% versus 22%, p<0.01), since diagnosis (42% versus 9%, p<0.05), and to report a history of intravenous drug use (50% versus 3%, p<0.01), but did not differ from heterosexual African-American men (n=15). No differences were found in reports of unprotected oral sex or recent use of hard drugs (i.e., crack, cocaine, heroin). These findings suggest that interventions targeting older African-American men (both gay/bisexual and heterosexual) with HIV/AIDS are needed to reduce risk behaviors and prevent HIV transmission in this population.     

A specific sexual orientation-related difference in navigation strategy

During spatial navigation, women typically navigate an environment using a landmark strategy, whereas men typically use an orientation strategy. To examine the as yet unknown effects of sexual orientation on these normative sex differences, this study required 80 healthy heterosexual and homosexual adult men and women to provide directions from experimental maps for 4 routes. The frequency and type of strategy used by each participant were computed. Expected sex differences were demonstrated, and a robust cross-sex shift was shown by homosexual men in using landmarks. This remained after controlling for differences in mental rotation, directional sense, and general intelligence. The findings may limit the number of putative neurodevelopmental pathways responsible for sex differences in navigation strategy utility.     

Men and women differ in amygdala response to visual sexual stimuli

Men are generally more interested in and responsive to visual sexually arousing stimuli than are women. Here we used functional magnetic resonance imaging (fMRI) to show that the amygdala and hypothalamus are more strongly activated in men than in women when viewing identical sexual stimuli. This was true even when women reported greater arousal. Sex differences were specific to the sexual nature of the stimuli, were restricted primarily to limbic regions, and were larger in the left amygdala than the right amygdala. Men and women showed similar activation patterns across multiple brain regions, including ventral striatal regions involved in reward. Our findings indicate that the amygdala mediates sex differences in responsiveness to appetitive and biologically salient stimuli; the human amygdala may also mediate the reportedly greater role of visual stimuli in male sexual behavior, paralleling prior animal findings.     

HIV risk behaviors among African American men in Los Angeles County who self-identify as heterosexual

There are limited data on high-risk behaviors among heterosexual African American men with HIV infection. Risk behaviors were examined in a case-control study of HIV-infected (n = 90) and uninfected (n = 272) African American men who self-identified as heterosexual. Of men who self-identified as heterosexual, 31% (n = 28) of the infected men and 16% (n = 43) of the uninfected men reported having had anal sex with men. Among the heterosexual men reporting anal sex with men, 100% of the infected and 67% of the uninfected men reported inconsistent condom use during anal sex with men. Few of the infected (12%) and uninfected (2%) men reported oral sex with other men. Of the men who self-identified as heterosexual, 46% of those who were HIV-positive and 37% of those who were HIV-negative reported anal sex with women with infrequent condom use. An increasing risk for HIV was associated with decreasing age at first sexual experience (chi2, 9.3; p = .002). A history of injecting drugs (odds ratio [OR], 3.1; 95% confidence intervals [CIs], 1.8, 5.4) and amphetamine (OR, 4.3; 95% CIs, 1.1, 16.7) and methamphetamine (OR, 2.9; 95% CIs, 1.4, 6.3) use were associated with HIV. Innovative HIV prevention strategies are needed that move beyond the traditional gay versus straight model to effectively access hard-to-reach African American men who self-identify as heterosexual.     

Homosexuality and illegal residency status in relation to substance abuse and personality traits among Mexican nationals

Maladaptive behavioral and personality reactions to severe stressors among Mexican homosexual men were assessed by comparing substance abuse and Rorschach data obtained from three samples: (a) homosexuals residing illegally in the United States (n = 40), (b) homosexuals living in Mexico (n = 21) and (c) heterosexuals living illegally in the United States (n = 25). The results of orthogonal contrasts showed very similar personality structure and substance abuse patterns among the participants in the two homosexual groups. As predicted, these men were found to be using alcohol or drugs to a greater extent than the heterosexual controls. Rorschach findings indicated that the homosexual subjects were experiencing dysphoric mood and distorted perceptions; they were also having significant difficulties coping with an environment that was discerned as increasingly dangerous. These results are relevant to the stress reduction hypothesis of addiction and provide quantitative information regarding the extent of psychopathology in this underserved Hispanic population.     

Sexual orientation and mental health in a birth cohort of young adults

BACKGROUND: This paper sought to examine the relationship between sexual orientation and mental health in a New Zealand birth cohort studied to age 25 years. METHOD: The analysis is based on a sample of 967 participants (469 males; 498 females) in the Christchurch Health and Development Study. As part of this study information was gathered on: (a) measures of sexual orientation, same-sex behaviour and sexual attraction obtained at ages 21 and 25 years; (b) measures of mental disorders and suicidal behaviours over the interval 21-25 years; (c) measures of childhood and family background. RESULTS: Latent class analysis was used to combine indicators of sexual orientation, same sex behaviour and attraction to form an empirically based classification of sexual orientation. The best-fitting model classified the sample into three groups: exclusively heterosexual orientation (87.6%); predominantly heterosexual but with same-sex inclinations or experience (9.6%); predominantly homosexual (2.8%). Proportionately more women than men were classified as predominantly heterosexual (14.2% v. 4.8% respectively) or predominantly homosexual (3.9% v. 1.5% respectively). Cohort members with a predominantly homosexual orientation had rates of mental disorder and suicidal behaviours that were between 1.5 and 12 times higher than for those with an exclusively heterosexual orientation. These associations persisted after adjustment for confounding. The associations between sexual orientation and mental health were more marked for males than females. CONCLUSIONS. The findings suggest a continuum of sexual preferences amongst young adults. Variations in sexual orientation were clearly associated with mental health. These associations tended to be stronger for males.     

Are all males equal? Anatomic and functional basis for sexual orientation in males.

In non-human primates anterior hypothalamic nuclei are closely involved in heterosexual activity in males. In humans, hypothalamic nuclei which correspond to these nuclei in non-human primates have been shown to have a neuronal density in homosexual men that is approximately half of that seen in heterosexual men. In addition, homosexual men exhibit a positive luteinizing hormone response to acutely administered estrogen that is intermediate between women (flat response) and heterosexual men (exaggerated response). Furthermore, on the basis of serum testosterone concentrations in similarly feminized transsexual males on estrogen/progestogen treatment 3 distinct groups can be identified. It is postulated that anatomic differences in the anterior hypothalamic nuclei that regulate sexual orientation in males may lead to alteration in the gonadotropin releasing hormone (GnRH) pulse/frequency leading to a more female-type pattern of gonadotropin secretion in homosexual males. Based on data in transsexual males this pattern may be more or less of the female-type in subsets of male homosexuals.     

Prevalence and correlates of HIV infection among young injection drug users in San Francisco

OBJECTIVE: We assessed the prevalence of HIV infection and associated risk behaviors among street-recruited young injection drug users (IDUs) in San Francisco. METHODS: In a cross-sectional study, 304 young (age <30 years) IDUs with a history of injecting in the previous 30 days were interviewed and tested for antibodies to HIV. Analyses assessing independent associations with HIV infection were limited to males only, due to the low number of infections in women. RESULTS: The prevalence of HIV infection was 5.3% overall but was highly stratified by gender and sexual preference (15.6% among homosexual/bisexual men vs. heterosexual men) and recruitment neighborhood (18% in the Polk Street area). Of 16 HIV infections, 14 (88%) were in males. Factors independently associated with HIV infection in males included sexual preference (homosexual/bisexual vs. heterosexual: adjusted odds ratio [AOR], 7.5; 95% confidence interval [CI], 1.5-36.6), recruitment neighborhood (Polk Street neighborhood vs. other neighborhoods: AOR, 4.8; 95% CI, 1.4-16.7), and duration of residence in San Francisco (>or=1 year vs. <1 year: AOR, 11.8; 95% CI, 1.4-95.8). CONCLUSIONS: The prevalence of HIV infection was highest among male IDUs who have sex with men. The strong associations between HIV infection and sexual orientation and HIV infection and recruitment locale suggest that risk may be attributable largely to sexual risk. In addition to successful prevention efforts aimed at reducing needle-associated risk, current intervention models aimed at young IDUs should target high-risk neighborhoods and emphasize sexual risk reduction measures, in particular among men who have sex with men.     

Partner notification and focused intervention as a means of identifying HIV-positive patients.

Partner notification as a means of contact tracing human immunodeficiency virus (HIV)-infected persons remains controversial. It is argued against by many gay activists, while primary public health officials and leaders in ethnic communities continue to support this as a means of identifying unknown cases. Human immunodeficiency virus-positive patients were interviewed to determine if partner notification could be a useful instrument. Based on interviews, patients at risk of infection through heterosexual contact were able to identify most of their sexual partners; the majority of these patients were women. Twenty-two of 22 women infected heterosexually were able to identify all of their sexual partners. Five of 8 heterosexual men were able to identify all of their sexual partners, but these men were infected through intravenous drug use. Six of 44 homosexual men interviewed were able to make these identifications. Two focus groups of homosexual men who were HIV-positive patients were organized; each was asked one question. Men in group B were asked if they could identify HIV-positive persons whom they suspected were not in a treatment program. Men in group A were asked if they they thought they knew HIV-positive persons still practicing unsafe sex. Thirteen of the 14 patients in group A were able to identify 30 persons they felt were still practicing unsafe sex; 17 of 30 tested HIV-positive and 9 were unaware of their status. The 14 patients in group B identified 15 persons they felt were HIV-positive; 11 were found to be HIV-positive and 8 were unaware of their status. These findings suggest that partner notification definitely has a role in heterosexual contact tracing, and focused intervention is a more cost-effective approach to early intervention.     

A survey of HIV infection and related high-risk factors among men who have sex with men in Suzhou,Jiangsu,China

A cross-sectional study using the snowball sampling method was conducted in May 2008 to investigate human immunodeficiency virus (HIV) infection status and related high risk factors among men who have sex with men (MSM) in Suzhou city of Jiangsu province. The researchers carried out a face-to-face questionnaire interview among MSM, and collected their blood samples to test for HIV and other sexually transmitted diseases (STDs). Among the 280 respondents, 91.1% had homosexual acts in the past 6 months and 87.5% had multiple homosexual partners; 46.4% had heterosexual sex in the past 6 months and 33.1% had multiple heterosexual partners. The rate of continued condom use was 44.3% in homosexual sex in the past 6 months, while the rate in heterosexual sex was 33.9%. Laboratory test results showed that the prevalences of HIV and syphilis were 7.1% (20/280) and 15.0% (42/280), respectively, but no HCV-positive person was found. In the multivariate logistic regression model, subjects with a monthly income of more than RMB $ 1,000 (OR=4.83,95% CI=1.44-16.22), subjects who often went to bars for sexual partners (OR=2.25, 95%CI=1.21-4.20), and subjects who had more than one sexual partner in the past 6 months (OR=0.49, 95%CI=0.25-0.97) and had sex with fixed sexual partners in the past 6 months (OR=0.42, 95%CI=0.25-0.75) were significantly associated with the rate of continued condom use in homosexual sex in the past 6 months. Unprotected sex and multiple sexual partners were more common among MSM in Suzhou city; furthermore, the prevalences of HIV infection and syphilis were relatively high. HIV preventive measures should be designed to address these risk factors and control the spread of HIV among MSM.     

Determinants of the presence of human papillomaviruses in the anal canal of Russian men

Knowledge of determinants of anal human papillomavirus (HPV) infections among men is still limited as most of the studies are focused on high‐risk populations and geographically narrowed. Such knowledge obtained in different populations is essential for better understanding of HPV natural history, transmission dynamics, and its role in the development and prevention of anogenital malignancies in different regions. Here we tested anal canal swab samples from 359 Russian heterosexual (323 human immunodeficiency virus [HIV]‐negative and 27 HIV‐positive, aged 18‐67 years) men attending a sexually transmitted infection clinic 36 HPV types using a proficient Luminex assay. HPV‐positivity in anal samples was common for 332 HIV‐negative heterosexual men for overall HPV (15.7%, n = 52), oncogenic HPV (9.6%, n = 32), nononcogenic HPV (8.1%, n = 27), and multiple HPV infections (4.5%, n = 14). The most common anal HPV types were HPV16 (5.7%), HPV45, and HPV51 (1.8% each), HPV66, and HPV87 (1.8% each). No association was found with the number of lifetime sexual partners, age of participants at the time of the study, or their sexual debut. Although anal HPV positivity was more common among HIV‐positive men, the current study provides additional evidence that anal HPV can be frequently detected in heterosexual HIV‐negative men favoring further studies on transmission routes to discriminate between contamination and true HPV infection.     

Male bisexual arousal: A matter of curiosity?

Conflicting evidence exists regarding whether bisexual-identified men are sexually aroused to both men and women. We hypothesized that a distinct characteristic, level of curiosity about sexually diverse acts, distinguishes bisexual-identified men with and without bisexual arousal. Study 1 assessed men's (n = 277) sexual arousal via pupil dilation to male and female sexual stimuli. Bisexual men were, on average, higher in their sexual curiosity than other men. Despite this general difference, only bisexual-identified men with elevated sexual curiosity showed bisexual arousal. Those lower in curiosity had responses resembling those of homosexual men. Study 2 assessed men's (n = 72) sexual arousal via genital responses and replicated findings of Study 1. Study 3 provided information on the validity on our measure of sexual curiosity by relating it to general curiosity and sexual sensation seeking (n = 83). Based on their sexual arousal and personality, at least two groups of men identify as bisexual.     

Characterization of risk factors for Helicobacter pylori infection among men attending a sexually transmitted disease clinic: lack of evidence for sexual transmission.

The mechanism of transmission of Helicobacter pylori is unknown. To investigate the role of sexual behavior and demographic factors in the acquisition of H. pylori infection, we evaluated the seroprevalence of antibody to H. pylori in 370 men attending an urban sexually transmitted diseases clinic. Sera from the following three groups were analyzed by enzyme-linked immunosorbent assay for H. pylori-specific immunoglobulin G: 78 human immunodeficiency virus (HIV)-seropositive homosexual men, 102 HIV-seronegative homosexual men, and 190 HIV-seronegative heterosexual men. Overall, the seroprevalence of H. pylori was 100 of 370 men (27%), with rates of 18% in HIV-seropositive homosexual men and 20% in HIV-seronegative homosexual men versus 35% in heterosexual men (P less than 0.005, chi 2 test). By ethnic group, 21 (12%) of 181 Caucasian men, 40 (41%) of 97 black men, and 37 (43%) of 87 Hispanic men were seropositive (P less than 0.001, chi 2 test). Multivariate analysis revealed that race was associated with H. pylori seropositivity independent of HIV status, sexual preference, or age. There was no relationship between H. pylori seropositivity and the number of lifetime sexual partners or previous sexually transmitted diseases. Three HIV-seropositive men with H. pylori immunoglobulin G had essentially identical antibody titers over 8 to 16 months of follow-up. In conclusion, black and Hispanic men have significantly higher H. pylori seroprevalence rates than do Caucasian men, but neither sexual behavior nor HIV infection influences the presence or persistence of H. pylori antibody. Further evaluation of the factors associated with these ethnic differences may lead to a better understanding of H. pylori acquisition and transmission.     

Interleukin 2 augmentation of natural killer cell activity in homosexual men with acquired immune deficiency syndrome

Natural killer cell activity of peripheral blood mononuclear cells against K562 myeloid cells was studied in 8 normal heterosexual men, 5 healthy homosexual men, and 11 homosexual men with acquired immune deficiency syndrome. The overall natural killer cell activity was lower in healthy homosexual men and in homosexual men with acquired immune deficiency syndrome. Peripheral blood mononuclear cells from four normal heterosexual men were preincubated overnight in complete medium supplemented with various concentrations of lectin-free interleukin 2 lacking interferon. Cells from these cultures exhibited a dose-dependent augmentation of natural killer cell activity. Peripheral blood mononuclear cells obtained from 8 normal heterosexuals, 5 healthy homosexuals, and 11 homosexual men with acquired immune deficiency syndrome were preincubated overnight in complete medium supplemented with 20% interleukin 2. Natural killer cell activity cultured in 20% interleukin 2 increased to 78.4 +/- 8.4 (mean +/- standard deviation) from 30.8 +/- 11.0 in normal heterosexual men, to 68.3 +/- 17.6 from 16.8 +/- 13.6 in healthy homosexual men and to 49.3 +/- 15.3 from 11.6 +/- 6.1 in homosexual men with acquired immune deficiency syndrome at a 100:1 effector/target cell ratio. These results suggest that interleukin 2 is capable of directly stimulating natural cell-mediated cytotoxicity. Consideration of the use of interleukin 2 as a potential therapeutic agent to modify immune responses in disorders such as acquired immune deficiency syndrome appears warranted.     

Uncovering category specificity of genital sexual arousal in women: The critical role of analytic technique

Based on analytic techniques that collapse data into a single average value, it has been reported that women lack category specificity and show genital sexual arousal to a large range of sexual stimuli including those that both match and do not match their self‐reported sexual interests. These findings may be a methodological artifact of the way in which data are analyzed. This study examined whether using an analytic technique that models data over time would yield different results. Across two studies, heterosexual (N = 19) and lesbian (N = 14) women viewed erotic films featuring heterosexual, lesbian, and gay male couples, respectively, as their physiological sexual arousal was assessed with vaginal photoplethysmography. Data analysis with traditional methods comparing average genital arousal between films failed to detect specificity of genital arousal for either group. When data were analyzed with smoothing regression splines and a within‐subjects approach, both heterosexual and lesbian women demonstrated different patterns of genital sexual arousal to the different types of erotic films, suggesting that sophisticated statistical techniques may be necessary to more fully understand women's genital sexual arousal response. Heterosexual women showed category‐specific genital sexual arousal. Lesbian women showed higher arousal to the heterosexual film than the other films. However, within subjects, lesbian women showed significantly different arousal responses suggesting that lesbian women's genital arousal discriminates between different categories of stimuli at the individual level. Implications for the future use of vaginal photoplethysmography as a diagnostic tool of sexual preferences in clinical and forensic settings are discussed.     

The time course of pupil dilation evoked by visual sexual stimuli: Exploring the underlying ANS mechanisms

The early processing of visual sexual stimuli shows signs of automaticity. Moreover, there is evidence for sex‐specific patterns in cognitive and physiological responding to erotica. However, little is known about the time course of rapid pupillary responses to sexual stimuli and their correspondence with other measures of autonomic activity in women and men. To study pupil dilation as an implicit measure of sexual arousal at various stages of picture processing, we presented 35 heterosexual participants with pictures showing either erotic couples or single (male/female) erotic nudes, contrasted with people involved in everyday situations. Brightness‐adjusted grayscale pictures were shown for a duration of 2,500 ms within the central visual field, alternating with perceptually matched patches. Left pupil diameter was recorded at 500 Hz using a video‐based eye tracker. Skin conductance and heart rate were coregistered and correlated with latent components of pupil dilation (dissociated by temporal PCA). Whereas stimulus‐evoked changes in pupil size indicated virtually no initial constriction, a rapid effect of appetence emerged (dilation to erotica within 500 ms). Responses at early stages of processing were remarkably consistent across both sexes. In contrast, later phases of pupil dilation, subjective ratings, and skin conductance responses showed a sex‐specific pattern. Moreover, evidence for an association of early‐onset pupil dilation and heart rate acceleration was found, suggestive of parasympathetic inhibition, whereas the late component was mainly related to sympathetically mediated skin conductance. Taken together, our results indicate that different temporal components of pupil responses to erotic stimuli may reflect divergent underlying neural mechanisms.