Blood-oxygenation-level-dependent functional magnetic resonance imaging for evaluating cerebral regions of female sexual arousal response

Specific factors and methodological decisions influencing brain responses to sexual stimuli in women

Most of the neuroimaging studies on sexual behavior have been conducted with male participants, leading to men-based models of sexual arousal. Here, possible factors and methodological decisions that might influence brain responses to sexual stimuli, specifically for the inclusion of women, will be reviewed. Based on this review, we suggest that future studies consider the following factors: menstrual phase, hormonal contraception use, history of sexual or psychiatric disorders or diseases, and medication use. Moreover, when researching sexual arousal, we suggest future studies assess sexual orientation and preferences, that women should select visual sexual stimuli, and a longer duration than commonly used. This review is thought to represent a useful guideline for future research in sexual arousal, which hopefully will lead to a higher inclusion of women and therefore more accurate neurobiological models of sexual arousal.

Understanding heterosexual women's erotic flexibility: the role of attention in sexual evaluations and neural responses to sexual stimuli

Many women experience desires, arousal and behavior that run counter to their sexual orientation (orientation inconsistent, 'OI'). Are such OI sexual experiences cognitively and neurobiologically distinct from those that are consistent with one's sexual orientation (orientation consistent, 'OC')? To address this question, we employed a mindful attention intervention-aimed at reducing judgment and enhancing somatosensory attention-to examine the underlying attentional and neurobiological processes of OC and OI sexual stimuli among predominantly heterosexual women. Women exhibited greater neural activity in response to OC, compared to OI, sexual stimuli in regions associated with implicit visual processing, volitional appraisal and attention. In contrast, women exhibited greater neural activity to OI, relative to OC, sexual stimuli in regions associated with complex visual processing and attentional shifting. Mindfully attending to OC sexual stimuli reduced distraction, amplified women's evaluations of OC stimuli as sexually arousing and deactivated the superior cerebellum. In contrast, mindfully attending to OI sexual stimuli amplified distraction, decreased women's evaluations of OI stimuli as sexually arousing and augmented parietal and temporo-occipital activity. Results of the current study constrain hypotheses of female erotic flexibility, suggesting that sexual orientation may be maintained by differences in attentional processing that cannot be voluntarily altered.

Altered Spontaneous Brain Activity in Women During Menopause Transition and Its Association With Cognitive Function and Serum Estradiol Level

OBJECTIVE

Serum hormone deficiencies during menopause transition may affect spontaneous brain activity and global cognition. The purpose of this study was to explore the differences in spontaneous brain activity between premenopausal and perimenopausal women, and to investigate the associations between spontaneous brain activity, serum hormone levels and global cognition.

METHODS

Thirty-two premenopausal women (47.75 ± 1.55 years) and twenty-five perimenopausal women (51.60 ± 1.63 years) underwent resting-state functional MRI (fMRI) scan. Clinical information including Mini-Mental State Examination (MMSE), levels of estradiol (E2), free testosterone, progesterone, prolactin, follicle-stimulating hormone and luteinizing hormone were measured. Regional homogeneity (ReHo) was used to evaluate spontaneous brain activity alterations between perimenopausal and premenopausal women. Correlation analysis was used to investigate the associations between brain functional alterations and clinical measures in perimenopausal group.

RESULTS

The results demonstrated increased ReHo value in the right lingual gyrus (LG) and decreased ReHo value in the right superior frontal gyrus (SFG) in perimenopausal women compared with premenopausal women. In perimenopausal group, ReHo of the right LG showed a negative correlation with level of E2 (r = -0.586, p = 0.002), ReHo of the right SFG showed a positive correlation with level of E2 (r = 0.470, p = 0.018) and MMSE (r = 0.614, p = 0.001).

CONCLUSIONS

The results demonstrated that women approaching menopause suffered from altered functions in brain regions related to cognitive function, working memory, the results also revealed a direct association between levels of E2 and brain functions in perimenopausal women.

The role of anterior and posterior insula in male genital response and in visual attention: an exploratory multimodal fMRI study

Several studies highlighted the role of insula on several functions and in sexual behavior. This exploratory study examines the relationships among genital responses, brain responses, and eye movements, to disentangle the role played by the anterior and posterior insula during different stages of male sexual response and during visual attention to sexual stimuli. In 19 healthy men, fMRI, eye movement, and penile tumescence data were collected during a visual sexual stimulation task. After a whole-brain analysis comparing neutral and sexual clips and confirming a role for the bilateral insulae, we selected two bilateral seed regions in anterior and posterior insula for functional connectivity analysis. Single-ROI-GLMs were run for the FC target regions. Single-ROI-GLMs were performed based on areas to which participants fixate: “Faces”, “Genitals,” and “Background” with the contrast “Genitals > Faces”. Single-ROI-GLMs with baseline, onset, and sustained PT response for the sexual clips were performed. We found stronger effects for the posterior than the anterior insula. In the target regions of the posterior insula, we found three different pathways: the first involved in visual attention, onset of erection, and sustained erection; the second involved only in the onset of erection, and the third limited to sustained erection.

Observing baby or sexual videos changes the functional synchronization between the prefrontal and parietal cortices in mothers in different postpartum periods

During the postpartum period (PP), mothers are more sensitive to sensory stimuli related to babies and less sensitive to those with sexual significance. The processing of emotional stimuli requires synchronization among different cerebral areas. This study characterized the cortical electroencephalographic (EEG) correlation in mothers from 1½ to 3 months (PP1), 4 to 5½ months (PP2) and over 6½ months, postpartum (PP3) while observing two videos: one of a baby (BV) and one with sexual content (SV). EEGs were recorded from the frontopolar, dorsolateral and parietal cortices. All three groups rated the BV as pleasant, but only PP3 reported higher sexual arousal with the SV. While watching the BV, PP1 showed a higher correlation among all cortical areas; PP2 manifested a decreased correlation between the prefrontal and parietal cortices, likely associated with the lower emotional modulation of the BV; and PP3 presented a higher synchronization among fewer cortical areas, probably related to longer maternal experience. These cortical synchronization patterns could represent adaptive mechanisms that enable the adequate processing of baby stimuli in new mothers. These data increase our knowledge of the cerebral processes associated with distinct sensitivities to the emotional stimuli that mothers experience during the PP.

Neuroanatomy and function of human sexual behavior: A neglected or unknown issue?

INTRODUCTION

Sexual desire, arousal, and orgasm are mediated by complex, yet still not fully understood, interactions of the somatic and autonomic nervous systems operating at the central and peripheral levels. Disruption of endocrine, neural, or vascular response, caused by aging, medical illness, neurological diseases, surgery, or drugs, can lead to sexual dysfunctions, thus significantly affecting patients' quality of life.

PURPOSE

This narrative review aims at characterizing the involvement of the central nervous system in human sexual behavior.

METHODS

A literature search was conducted using PubMed in its entirety up to June 2018, analyzing the studies dealing with the neurobiological and neurophysiological basis of human sexuality.

RESULTS

Sexual behavior is regulated by both subcortical structures, such as the hypothalamus, brainstem, and spinal cord, and several cortical brain areas acting as an orchestra to finely adjust this primitive, complex, and versatile behavior. At the central level, dopaminergic and serotonergic systems appear to play a significant role in various factors of sexual response, although adrenergic, cholinergic, and other neuropeptide transmitter systems may contribute as well.

CONCLUSIONS

Providing healthcare professionals with information concerning sexual behavior may overcome useless and sometimes dangerous barriers and improve patient management, since sexual well-being is considered one of the most important aspects of one's quality of life.

Brain Morphological Changes With Functional Deficit Associated With Sexual Arousal in Postmenopausal Women

INTRODUCTION

We have not known how menopause synchronously influences brain morphology and function associated with visually stimulated sexual arousal in postmenopausal women.

AIM

This study used a combination of functional magnetic resonance imaging and voxel-based morphometry to evaluate menopause-related brain morphological and functional changes in postmenopausal women.

METHODS

Nineteen premenopausal women and 19 postmenopausal women underwent functional and structural magnetic resonance imaging. Brain function activity was measured while the subjects viewed an erotic video clip.

MAIN OUTCOME MEASURES

A 2-sample t-test was used for cross-analysis of the 2 groups for comparison of gray matter volumes (corrected P < .05) and brain activation (uncorrected P < .01).

RESULTS

Our study revealed a relationship between sexual function and morphological changes in postmenopausal women. Compared with premenopausal women, the postmenopausal group showed significantly lower brain activations in the major parts of the limbic system and basal ganglia, including the parahippocampal gyrus, head of caudate nucleus, insula, putamen, hippocampus, hypothalamus, amygdala, and globus pallidus, which are involved in sexual behavior and emotional responses. In morphometric analyses, postmenopausal women showed significantly decreased gray matter volumes of the insula, putamen, parahippocampal gyrus, amygdala, and anterior cingulate gyrus, most of which were associated with decreased functional activity during visual sexual arousal in postmenopausal women. In addition, the premenopausal group alone showed a positive correlation between the activity of the insula and the level of estradiol (Pearson correlation r = 0.588; P = .008).

CONCLUSION

This study demonstrates an association between menopause-related brain function and morphological changes in postmenopausal women. This finding provides insight into the neural mechanisms associated with the sexual functional deficit in postmenopausal women. Baek H-S, Kim G-W, Sundaram T, et al. Brain Morphological Changes with Functional Deficit Associated with Sexual Arousal in Postmenopausal Women. Sex Med 2019;7:480-488.

Effect of Sex Hormones on Brain Connectivity Related to Sexual Function in Perimenopausal Women: A Resting-State fMRI Functional Connectivity Study

BACKGROUND

Perimenopause is associated with increased risk of depression, vasomotor symptoms, and sexual dysfunction.

AIMS

To explore the effect of sex hormones on the functional connectivity (FC) of different brain regions related to sexual function in perimenopausal women.

METHODS

32 premenopausal women (mean age, 47.75 ± 1.55 years) and 25 perimenopausal women (mean age, 51.60 ± 1.63 years) underwent sex hormone level measurements and resting-state fMRI.

MAIN OUTCOME MEASURES

Serum levels of sex hormones, including prolactin (PRL), follicle-stimulating hormone (FSH), luteotropic hormone (LH), estradiol (E2), free testosterone (free-T), and progesterone (P), were measured. 10 brain regions related to sexual function were selected according to a meta-analysis, and FCs of the selected regions of interest were calculated as Pearson's correlation coefficient.

RESULTS

Compared with premenopausal women, perimenopausal women showed increased FC between the right area 13 (A13_r) and the right medial superior frontal gyrus (mSFG), between the left dorsal granular insula (dIg_L) and the right superior frontal gyrus (SFG) (Gaussian random field-corrected at the voxel level, P < .001, and cluster level, P < .025). Furthermore, the PRL level was negatively correlated with the FC of A13_R with the right mSFG and the FC of dIg_L with the right SFG.

CLINICAL TRANSLATION

These findings may be applicable to assessing brain dysfunction with FC changes in women approaching menopause.

STRENGTHS & LIMITATIONS

This study is the first to evaluate a direct relationship between sex hormone levels and brain FC changes in women approaching menopause. Sexual function was not assessed, which may weaken the conclusions related to sexual function.

CONCLUSIONS

The results show that women approaching menopause suffered from aberrant intrinsic FC in regions related to sexual function, and reveal a direct relationship between serum sex hormone levels and FC changes related to sexual function. Lu W, Guo W, Cui D, et al. Effect of Sex Hormones on Brain Connectivity Related to Sexual Function in Perimenopausal Women: A Resting-State fMRI Functional Connectivity Study. J Sex Med 2019;16:711-720.

A Pilot Study of a Topical Intervention for Treatment of Female Sexual Dysfunction

PURPOSE/BACKGROUND

Many investigators reported that pharmacological treatment of female sexual dysfunction (FSD) has been a promising field yet to be explored. The purpose of this pilot study was to investigate the efficacy and safety of a topical cream containing small concentrations of three vasodilators with different mechanisms of action in treating FSD.

METHODS

In this randomized, controlled pilot trial, premenopausal (n = 30) and postmenopausal (n = 30) cases of 21- to 62-year age range with FSD were allocated randomly into 15 given placebo or 15 given active cream in each group. The women included had FSD for more than a 6-month duration and a total score of Female Sexual Distress Scale-Revised of at least 15. Assessing sexual function by measuring female sexual function index (FSFI) during five clinic visits, one at the end of baseline week and at the end of each week of the 4-week treatment period. The primary end point was changed from baseline FSFI total scores to week 4 treatment. Secondary end point included the changes from baseline arousal, desire, orgasm, and satisfaction scores to week 4 treatment.

FINDINGS/RESULTS

The sexual problem reported by patients was orgasmic or/and arousal disorders. In premenopausal cases, active cream led to a high significant increase in mean change FSFI total score from the baseline to week 4 compared with placebo (1.7 ± 1.886 vs 13.35 ± 4.646, respectively; P < 0.0001). Greater improvement of mean change of orgasm and arousal domain score was also observed (0.3 ± 0.45 and 0.35 ± 0.39 vs. 2.66 ± 0.63 and 1.87 ± 0.168, respectively; P < 0.0001). In postmenopausal cases, there were significantly greater improvements with active cream in all sexual functions compared with placebo cream (P < 0.0001). In triple cream, mean change of FSFI total score, orgasm domain score, and arousal score domain were 14.85 ± 6.33, 1.87 ± 0.168 and 2.66 ± 1.182, whereas in the placebo cream, they were 1.54 ± 2.1,0.7 ± 0.76 and 0.22 ± 0.44, respectively. Meanwhile, orgasm scores increased significantly after the use of placebo cream. No serious adverse effects were reported during treatment.

IMPLICATIONS/CONCLUSIONS

The results of the pilot trial suggest that topical cream containing small concentrations of three vasodilators may act synergistically, and was effective in improving arousal, orgasmic, and satisfaction disorder with a safer profile for premenopausal and postmenopausal women with FSD. Further studies are recommended to be conducted using a large number of nondepressive and depressive patients.

The Role of Ovarian Hormones and the Medial Amygdala in Sexual Motivation

Purpose

Although research into the neurobiology of sexual desire in women is active, relatively little is understood about the origins of sexual motivation in women. The purpose of our review is to discuss factors that influence a central sexual motivate state and generalized arousal as potential drivers of sexual motivation in women and female rats.

Recent Findings

Sexual motivation is the product of interactions of the central motive state and salient sexually-relevant cues. Ovarian hormones and generalized arousal influence the central motive state, and endogenous levels of estradiol and progesterone correlate with sexual motivation and behavior in women. The amygdala is a key integratory site for generalized arousal and sexual sensory stimulation, which could then increase sexual motivation through its downstream projections.

Summary

Our model of enhanced female sexual motivation suggests that the combined effects of dopamine and progesterone receptor activation in the medial amygdala increases the incentive properties of a sexual stimulus. Further study into the interactions of ovarian hormones and mediators of generalized arousal on the processing of sexually-relevant cues informs our understanding of the neurobiology of female sexual motivation and could lead to the development of therapeutics to treat the dysfunctions of sexual desire in women.

The Physiology of Female Sexual Function and the Pathophysiology of Female Sexual Dysfunction (Committee 13A)

INTRODUCTION

The article consists of six sections written by separate authors that review female genital anatomy, the physiology of female sexual function, and the pathophysiology of female sexual dysfunction but excluding hormonal aspects.

AIM

To review the physiology of female sexual function and the pathophysiology of female sexual dysfunction especially since 2010 and to make specific recommendations according to the Oxford Centre for evidence based medicine (2009) "levels of evidence" wherever relevant.

CONCLUSION

Recommendations were made for particular studies to be undertaken especially in controversial aspects in all six sections of the reviewed topics. Despite numerous laboratory assessments of female sexual function, genital assessments alone appear insufficient to characterise fully the complete sexual response.

Menopause-related brain activation patterns during visual sexual arousal in menopausal women: An fMRI pilot study using time-course analysis

The aging process and menopausal transition are important factors in sexual dysfunction of menopausal women. No neuroimaging study has assessed the age- and menopause-related changes on brain activation areas associated with sexual arousal in menopausal women. The purpose of this study was to evaluate the time course of regional brain activity associated with sexual arousal evoked by visual stimulation in premenopausal and menopausal women, and further to assess the effect of menopause on the brain areas associated with sexual arousal in menopausal women using functional magnetic resonance imaging (fMRI). Thirty volunteers consisting of 15 premenopausal and 15 menopausal women underwent the fMRI. For the activation condition, volunteers viewed sexually arousing visual stimulation. The brain areas with significantly higher activation in premenopausal women compared with menopausal women included the thalamus, amygdala, and anterior cingulate cortex (ACC) using analysis of covariance adjusting for age (p<0.005). Blood-oxygen-level-dependent signal changes in the amygdala while viewing erotic video were positively correlated with estrogen levels in the two groups. Our findings suggest that reduced brain activity of the thalamus, amygdala, and ACC in menopausal women may be associated with menopause-related decrease in sexual arousal. These findings might help elucidate the neural mechanisms associated with sexual dysfunction in menopausal women.

Peripheral Female Genital Arousal as Assessed by Thermography Following Topical Genital Application of Alprostadil vs Placebo Arousal Gel: A Proof-of-Principle Study Without Visual Sexual Stimulation

Introduction

Female sexual arousal disorder is a pathophysiologic state characterized clinically by persistent or recurrent inability to attain or maintain an adequate lubrication-swelling response of sexual excitement until completion of sexual activity. Prior clinical experience with alprostadil products for men with erectile dysfunction supports its use in women with female sexual arousal disorder.

Aim

To compare the effect of topical alprostadil with over-the-counter (OTC) lubricant on female genital arousal in the absence of visual sexual stimuli.

Methods

Healthy premenopausal women without sexual dysfunction were recruited from the community to participate in the study. Of 17 women who consented, 10 were enrolled and completed the trial. The mean age of subjects was 32 years (range = 27–43). Study drug or placebo was applied topically to the genitals. Continuous temperature monitoring was performed. Participants completed questionnaires assessing genital sensation, effect, intensity, and duration.

Main Outcome Measures

Change in temperature from baseline in vestibule, clitoris and vulva.

Results

In all 10 subjects, topical alprostadil induced a statistically significant increase in temperature of the vestibule, clitoris, and vulva compared with the OTC lubricant. The most rapid difference in genital temperature between placebo and alprostadil was seen on the vulva, which demonstrated a significant difference at approximately 9 minutes. There was a significant difference in temperature seen for the vestibule and clitoris at 11 and 19 minutes, respectively. Sixty percent of women reported being aware or conscious of genital sensations with topical alprostadil, but not with OTC lubricant. Discordance was noted in 30% of subjects who reported being aware or conscious of genital sensations with the two treatments and 10% who reported not being aware or conscious of genital sensations with either treatment.

Conclusion

Topical alprostadil administered to healthy premenopausal women induced statistically significant, sustained increases in genital temperatures of the vestibule, clitoris, and vulva within 20 minutes compared with OTC lubricant.

Neural substrates of sexual arousal in heterosexual males: event-related fMRI investigation

BACKGROUND

Sexual behavior is an important role for the survival of species. The advancement of brain imaging methods has enabled the understanding of the brain mechanism related to sexual arousal. The previous studies on the brain mechanism related to sexual arousal have mostly conducted on block design paradigm.

METHODS

Despite its requirement for stricter experimental control, the event-related paradigm is known to be more efficient in detecting instant emotional and cognitive responses. The paradigm also enables the observation of hemodynamic responses through time. Therefore, this study used the event-related fMRI to examine the brain activation in various areas associated with sexual arousal as well as changes in hemodynamic responses with time.

RESULTS

Strong activations were observed in the various areas associated with sexual arousal comprised of various factors: (1) activation areas related to cognitive factors: the occipital lobe and parietal lobe; (2) activation areas related to emotional factors: the thalamus and amygdala; (3) activation areas related to motivational factors: the anterior cingulate gyrus, orbitofrontal cortex, and insula; and (4) activation areas related to physiological factors: the precentral gyrus, putamen, and globus pallidus. We also identified the activation of the putamen and globus pallidus that were not well observed in previous block design studies. In the result of the hemodynamic response, the neural activity in those areas showed more transient aspects of the hemodynamic responses relative to the neural activity of other areas.

CONCLUSIONS

These results suggested that the event-related paradigm is better at detecting the neural activity of the brain regions, which tend to appear suddenly, but disappear soon.

Hypoactive Sexual Desire Disorder: A Review of Epidemiology, Biopsychology, Diagnosis, and Treatment

INTRODUCTION

Hypoactive Sexual Desire Disorder (HSDD) is defined in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Revised (DSM-IV-TR) as persistent deficient sexual fantasies and desire for sexual activity that causes marked distress or interpersonal difficulty. In the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), HSDD has been subsumed by Female Sexual Interest/Arousal Disorder. However, decades of research based on DSM-IV-TR HSDD criteria form the foundation of our understanding of the essential symptom of distressing low sexual desire, its epidemiology, clinical management, and treatment.

AIM

This publication reviews the state of knowledge about HSDD.

METHODS

A literature search was performed using terms HSDD and female sexual dysfunction (FSD).

MAIN OUTCOME MEASURES

Physicians acknowledge that FSD is common and distressing; however, they infrequently address it, citing low confidence, time constraints, and lack of treatment as barriers.

RESULTS

HSDD is present in 8.9% of women ages 18 to 44, 12.3% ages 45 to 64, and 7.4% over 65. Although low sexual desire increases with age, distress decreases; so prevalence of HSDD remains relatively constant across age. HSDD is associated with lower health-related quality of life; lower general happiness and satisfaction with partners; and more frequent negative emotional states. HSDD is underdetected and undertreated. Less than half of patients with sexual problems seek help from or initiate discussions with physicians. Patients are inhibited by fear of embarrassing physicians and believe that physicians should initiate discussions. The Decreased Sexual Desire Screener, a tool for detecting and diagnosing HSDD, is validated for use in general practice.

CONCLUSION

Women can benefit from intervention in primary care, behavioral health and sexual medicine settings. Psychotherapeutic and pharmacological interventions aim to enhance sexual excitatory process and decrease inhibitory processes. Flibanserin, the first centrally acting daily medication for HSDD, was recently approved in the US for premenopausal women.

Brain activation-based sexual orientation in female-to-male transsexuals

This study was performed to identify the sexual orientation in association with brain activation pattern in response to visual erotic stimuli in female-to-male (FtM) transsexuals by using functional magnetic resonance imaging (fMRI). Eleven FtM transsexuals who have had sex-reassignment surgery to alter their natal bodies with the gender-identity disorder were participated. Brain activation for sexual orientation was induced by visual stimuli with female and male erotic nude pictures compared with emotionally-neutral pictures. During viewing the erotic female pictures, the brain areas dominantly activated consist of the superior frontal gyrus, supplementary motor area, anterior/median cingulate gyri and hypothalamus, whereas during viewing male pictures, the brain areas with predominant activities were the middle frontal gyrus, precentral gyrus, middle temporal gyrus, fusiform gyrus, angular gyrus, precuneus, superior/middle occipital gyri, cerebellar cortex and vermis. These findings demonstrate that the brain activation patterns induced by viewing male or female erotic pictures show some correlation to the sexual orientation opposite to the genetic sex in FtM transsexuals. This study would be helpful to understand the neural mechanism associated with visual sexual arousal in patients with gender disorder.

A comparative study of brain activation patterns associated with sexual arousal between males and females using 3.0-T functional magnetic resonance imaging

Background In contrast to the previous studies using a 1.5-T magnetic resonance imaging system, our study was performed on a higher magnetic field strength, 3.0 T, to gain more valuable information on the functional brain anatomy associated with visual sexual arousal for discriminating the gender difference by increasing the detection power of brain activation. Methods: Twenty-four healthy subjects consisting of 12 males and 12 females underwent functional magnetic resonance imaging examination for this study. Brain activity was measured while viewing erotic videos. Results: The predominant activation areas observed in males as compared with females included the hypothalamus, the globus pallidus, the head of the caudate nucleus, the parahippocampal gyrus, the amygdala and the septal area, whereas the predominant activation in females was observed in the anterior cingulate gyrus and the putamen. Conclusion: Our findings suggest that the brain activation patterns associated with visual sexual arousal are specific to gender. This gender difference in brain activation patterns is more remarkable at higher magnet field (3.0 T) than at 1.5 T.

Brain neuronal activation induced by flibanserin treatment in female rats

RATIONALE

Flibanserin, a 5-HT1A agonist and 5-HT2A antagonist, is developed for the treatment of hypoactive sexual desire disorder in women, and its efficacy has been evidenced in several clinical studies. Flibanserin prosexual effects have been also evidenced in preclinical animal models. However, the mechanism of action of flibanserin remains not fully understood.

OBJECTIVE

The aim of the present study was to examine brain neuronal activation in female rats treated with flibanserin, using single immunocytochemical labeling of Fos protein, a marker of neuronal activation, and co-localization of Fos and catecholaminergic marker.

METHOD

Six groups of female rats received either acute or chronic administrations of vehicle, flibanserin 15 mg/kg or flibanserin 45 mg/kg. The brains were collected and processed for immunocytochemical labeling.

RESULTS

Acute flibanserin increased levels of Fos immunoreactivity in the nucleus accumbens, arcuate hypothalamic nucleus, locus coeruleus, lateral paragigantocellular nucleus, and nucleus of the solitary tract. Chronic 22-day treatment with flibanserin increased Fos expression in the medial preoptic area and arcuate nucleus of the hypothalamus, ventral tegmental area, locus coeruleus, and lateral paragigantocellular nucleus. Both acute and chronic flibanserin increased the density of activated catecholaminergic neurons in the ventral tegmental area but not in the locus coeruleus.

CONCLUSION

Altogether, our results showed that flibanserin, at the dose known to enhance female sexual motivation, preferentially activated the brain regions belonging to the mesolimbic dopaminergic pathway and hypothalamic structures involved in the integration of sexual cues related to sexual motivation.

Neural correlates of sexual arousal in heterosexual and homosexual women and men

Most men have a category-specific pattern of genital and subjective sexual arousal, responding much more strongly to erotic stimuli depicting their preferred sex than to erotic stimuli depicting their nonpreferred sex. In contrast, women tend to have a less specific arousal pattern. To better understand this sex difference, we used neuroimaging to explore its neural correlates. Heterosexual and homosexual women viewed erotic photographs of either men or women. Evoked neural activity was monitored via fMRI and compared with responses to the same stimuli in heterosexual and homosexual men. Overall, a network of limbic (as well as the anterior cingulate) and visual processing regions showed significantly less category-specific activity in women than men. This was primarily driven by weaker overall activations to preferred-sex stimuli in women, though there was also some evidence of stronger limbic activations to nonpreferred-sex stimuli in women. Primary results were similar for heterosexual and homosexual participants. Women did show some evidence of category-specific responses in the visual processing regions, although even in these regions they exhibited less differential activity than men. In the anterior cingulate, a region with high concentrations of sex-hormone receptors, subjective and neural category specificity measures correlated positively for women but negatively for men, suggesting a possible sex difference in the role of the anterior cingulate. Overall, results suggest that men tend to show more differentiated neural responses than do women to erotic photographs of one sex compared to the other sex, though women may not be entirely indifferent to which sex is depicted.

Oxytocin, motivation and the role of dopamine

The hypothalamic neuropeptide oxytocin has drawn the attention of scientists for more than a century. The understanding of the function of oxytocin has expanded dramatically over the years from a simple peptide adept at inducing uterine contractions and milk ejection to a complex neuromodulator with a capacity to shape human social behavior. Decades of research have outlined oxytocin's ability to enhance intricate social activities ranging from pair bonding, sexual activity, affiliative preferences, and parental behaviors. The precise neural mechanisms underlying oxytocin's influence on such behaviors have just begun to be understood. Research suggests that oxytocin interacts closely with the neural pathways responsible for processing motivationally relevant stimuli. In particular, oxytocin appears to impact dopaminergic activity within the mesocorticolimbic dopamine system, which is crucial not only for reward and motivated behavior but also for the expression of affiliative behaviors. Though most of the work performed in this area has been done using animal models, several neuroimaging studies suggest similar relationships may be observed in humans. In order to introduce this topic further, this paper will review the recent evidence that oxytocin may exert some of its social-behavioral effects through its impact on motivational networks.

Brain activation patterns in women with acquired hypoactive sexual desire disorder and women with normal sexual function: a cross-sectional pilot study

OBJECTIVE

To examine and compare brain activation patterns of premenopausal women with normal sexual function and those with hypoactive sexual desire disorder (HSDD) during viewing of validated sexually explicit film clips.

DESIGN

Cross-sectional pilot study.

SETTING

University-based clinical research center.

PATIENT(S)

Premenopausal women.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Areas of brain activation during viewing of sexually explicit film clips.

RESULT(S)

Women with normal sexual function showed significantly greater activation of the right thalamus, left insula, left precentral gyrus, and left parahippocampal gyrus in comparison with women with HSDD, who exhibited greater activation of the right medial frontal gyrus and left precuneus regions.

CONCLUSION(S)

Women with HSDD may have alterations in activation of limbic and cortical structures responsible for acquiring, encoding, and retrieving memory, the processing and memory of emotional reactions, and areas responsible for heightened attention to one's own physical state.

Gender commonalities and differences in the neural processing of visual sexual stimuli

INTRODUCTION

Few studies so far have directly compared the neural processing of visual sexual stimuli in men and women. Also, most of these studies only compared sexual with neutral stimuli, making it difficult to disentangle sexual stimulus processing from general emotional processing.

AIM

The current study aimed to explore gender commonalities and differences in neural activity associated with the processing of visual sexual stimuli in a large sample of 50 men and 50 women. In order to disentangle effects of sexual processing from those of general emotional processing, we employed sexual, neutral, positive, and negative emotional pictures.

METHODS

Subjects passively viewed sexual, neutral, positive, and negative emotional pictures during a functional magnetic resonance imaging (fMRI) session. Pictures were presented in 24 blocks of five pictures each. Every block was rated immediately after its presentation with respect to valence, arousal, and sexual arousal.

MAIN OUTCOME MEASURES

Blood oxygen level dependent responses measured by fMRI and subjective ratings.

RESULTS

fMRI analysis revealed a distributed network for the neural processing of sexual stimuli comprising the hypothalamus, the nucleus accumbens, as well as orbitofrontal, occipital, and parietal areas. This network could be identified (i) for both men and women, with men showing overall stronger activations than women and (ii) independent of general emotional arousal or valence effects.

CONCLUSION

Our data speak in favor of a common neural network associated with the processing of visual sexual stimuli in men and women. Apart from the observed gender commonalities, overall stronger responses in men were observed that might indicate stronger sexual responsivity in men.

Assessment of brain metabolites change during visual sexual stimulation in healthy women using functional MR spectroscopy

INTRODUCTION

Numerous functional magnetic resonance imaging (fMRI) studies demonstrated the key brain areas associated with visual sexual arousal. However, the changes in brain metabolites involved in sexual stimuli have not been reported.

AIM

This study utilized functional MR spectroscopy (fMRS) to evaluate the changes in brain metabolites associated with sexual arousal induced by stimulation with erotic video clips in healthy women.

METHODS

Twenty-three healthy, right-handed women (38.4 ± 10.0 years) participated in (1) H-fMRS and fMRI studies. T1 and T2 MR images were used for voxel localization of the anterior cingulate gyrus, which is one of the most important key centers associated with sexual arousal.

MAIN OUTCOME MEASURES

The changes of brain metabolites were measured using (1) H-fMRS during time-course activation: "before," "during," and "after" visual sexual stimulation. The time-course variation of the brain metabolites was analyzed by the repeated-measures analysis of variance.

RESULTS

The CVmean of all the metabolites had <30% (range, 9-29%). The ICCs of α-glutamine-glutamate (Glx), choline (Cho), β·γ-Glx, N-acetylaspartate (NAA) and lactate (Lac) all exceeded 0.6. However, myo-inositol (mI) and lipid (Lip) were <0.6. The concentration of brain metabolites including α-Glx, β·γ-Glx, Cho, and Lac comparatively increased significantly during visual sexual stimulation.

CONCLUSIONS

(1) H-fMRS, for the first time, was applied to assess the brain metabolic changes during visually-evoked sexual arousal. The fMRS outcomes in relation to functional MRI data will be useful to understand the neural mechanism associated with sexual arousal.

Gender difference in brain activation to audio-visual sexual stimulation; do women and men experience the same level of arousal in response to the same video clip?

Factors related to sexual arousal are different in men and women. The conditions for women to become aroused are more complex. However, the conventional audio-visual stimulation (AVS) materials used to evaluate sexual arousal are universal. In the present study, we investigated sexual differences in the response to different types of AVS by studying activated areas of the brain using functional magnetic resonance imaging (fMRI). fMRI was performed during two types of AVS in 20 healthy heterosexual volunteers (aged 20-28 years, 10 men and 10 women). The two AVS types were: (1) mood type, erotic video clips with a concrete story and (2) physical type, directly exposing sexual intercourse and genitalia. fMRI images were analyzed and compared for each stimulation with a Mann-Whitney U test, with statistical significance set at P<0.05. Men preferred the physical type of AVS to the mood type (mean arousal score 2.14 vs 1.86 in females) and women preferred the mood type (mean arousal score 2.14 vs 1.86 in males) (P<0.05). Degrees of activation in brain areas differed between genders and types of AVS for each gender. This should be considered when applying the AVS method to evaluate and diagnose female sexual dysfunction.

Effects of antidepressant treatment on sexual arousal in depressed women: a preliminary FMRI study

OBJECTIVE

There was a recent study to explore the cerebral regions associated with sexual arousal in depressed women using functional magnetic resonance imaging (fMRI). The purpose of this neuroimaging study was to investigate the effects of antidepressant treatment on sexual arousal in depressed women.

METHODS

SEVEN DEPRESSED WOMEN WITH SEXUAL AROUSAL DYSFUNCTION (MEAN AGE: 41.7±13.8, mean scores of the Beck Depression Inventory (BDI) and the 17-item Hamilton Rating Scale for Depression (HAMD-17): 35.6±7.1 and 34.9±3.1, respectively) and nine healthy women (mean age: 40.3±11.6) underwent fMRI before and after antidepressant treatment. The fMRI paradigm contrasted a 1 minute rest period viewing non-erotic film with 4 minutes of sexual stimulation viewing an erotic video film. Data were analyzed by SPM 2. The relative number of pixels activated in each period was used as an index of activation. All depressed women were treated with mirtazapine (mean dosage: 37.5 mg/day) for 8 to 10 weeks.

RESULTS

Levels of brain activity during sexual arousal in depressed women significantly increased with antidepressant treatment (p<0.05) in the regions of the hypothalamus (3.0% to 11.2%), septal area (8.6% to 27.8%) and parahippocampal gyrus (5.8% to 14.6%). Self-reported sexual arousal during visual sexual stimulation also significantly increased post-treatment, and severity of depressive symptoms improved, as measured by the BDI and HAMD-17 (p<0.05).

CONCLUSION

These results show that sexual arousal dysfunction of depressed women may improve after treatment of depression, and that this improvement is associated with increased activation of the hypothalamus, septal area, and parahippocampal gyrus during sexual arousal.

Brain activation in response to visually evoked sexual arousal in male-to-female transsexuals: 3.0 tesla functional magnetic resonance imaging

Objective

This study used functional magnetic resonance imaging (fMRI) to contrast the differential brain activation patterns in response to visual stimulation with both male and female erotic nude pictures in male-to-female (MTF) transsexuals who underwent a sex reassignment surgery.

Materials and Methods

A total of nine healthy MTF transsexuals after a sex reassignment surgery underwent fMRI on a 3.0 Tesla MR Scanner. The brain activation patterns were induced by visual stimulation with both male and female erotic nude pictures.

Results

The sex hormone levels of the postoperative MTF transsexuals were in the normal range of healthy heterosexual females. The brain areas, which were activated by viewing male nude pictures when compared with viewing female nude pictures, included predominantly the cerebellum, hippocampus, putamen, anterior cingulate gyrus, head of caudate nucleus, amygdala, midbrain, thalamus, insula, and body of caudate nucleus. On the other hand, brain activation induced by viewing female nude pictures was predominantly observed in the hypothalamus and the septal area.

Conclusion

Our findings suggest that distinct brain activation patterns associated with visual sexual arousal in postoperative MTF transsexuals reflect their sexual orientation to males.

Functional neuroimaging studies of sexual arousal and orgasm in healthy men and women: a review and meta-analysis

In the last fifteen years, functional neuroimaging techniques have been used to investigate the neuroanatomical correlates of sexual arousal in healthy human subjects. In most studies, subjects have been requested to watch visual sexual stimuli and control stimuli. Our review and meta-analysis found that in heterosexual men, sites of cortical activation consistently reported across studies are the lateral occipitotemporal, inferotemporal, parietal, orbitofrontal, medial prefrontal, insular, anterior cingulate, and frontal premotor cortices as well as, for subcortical regions, the amygdalas, claustrum, hypothalamus, caudate nucleus, thalami, cerebellum, and substantia nigra. Heterosexual and gay men show a similar pattern of activation. Visual sexual stimuli activate the amygdalas and thalami more in men than in women. Ejaculation is associated with decreased activation throughout the prefrontal cortex. We present a neurophenomenological model to understand how these multiple regional brain responses could account for the varied facets of the subjective experience of sexual arousal. Further research should shift from passive to active paradigms, focus on functional connectivity and use subliminal presentation of stimuli.

Opposed hemispheric specializations for human hypersexuality and orgasm?

With a multiple case report analysis we demonstrate that hypersexuality more often results from right hemisphere (RH) (n=26) than left hemisphere (LH) (n=7) lesions, possibly because of LH release after the RH lesion, and that ictal orgasm more often occurs in patients with right-sided (n=23) than left-sided (n=8) seizure foci, with the symptom probably resulting from RH activation. The LH may be specialized for increasing sexual tension, whereas the RH may be specialized for release of this tension (orgasm), the former being catabolic and the latter anabolic. Several other interpretations of the findings are also discussed.

Future sexual medicine physiological treatment targets

INTRODUCTION

Sexual function in men and women incorporates physiologic processes and regulation of the central and peripheral nervous systems, the vascular system, and the endocrine system. There is need for state-of-the-art information as there is an evolving research understanding of the underlying molecular biological factors and mechanisms governing sexual physiologic functions.

AIM

To develop an evidence-based, state-of-the-art consensus report on the current knowledge of the major cellular and molecular targets of biologic systems responsible for sexual physiologic function.

METHODS

State-of-the-art knowledge representing the opinions of seven experts from four countries was developed in a consensus process over a 2-year period.

MAIN OUTCOME MEASURES

Expert opinion was based on the grading of evidence-based medical literature, widespread internal committee discussion, public presentation, and debate.

RESULTS

Scientific investigation in this field is needed to increase knowledge and foster development of the future line of treatments for all forms of biological-based sexual dysfunction. This article addresses the current knowledge of the major cellular and molecular targets of biological systems responsible for sexual physiologic function. Future treatment targets include growth factor therapy, gene therapy, stem and cell-based therapies, and regenerative medicine.

CONCLUSIONS

Scientific discovery is critically important for developing new and increasingly effective treatments in sexual medicine. Broad physiologic directions should be vigorously explored and considered for future management of sexual disorders.

Low sexual desire--is it all in her head? Pathophysiology, diagnosis, and treatment of hypoactive sexual desire disorder

Hypoactive sexual desire disorder (HSDD) is thought to be the most prevalent form of female sexual dysfunction (FSD), affecting up to 1 in 10 US women. Hypoactive sexual desire disorder is defined by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) as persistent or recurrent deficiency or absence of sexual fantasies and thoughts, and/or desire for, or receptivity to, sexual activity, which causes personal distress or interpersonal difficulties and is not caused by a medical condition or drug. This definition has recently received criticism and recommendations for changes encompass the inclusion of duration, intensity, and frequency, and the elimination of distress as a diagnostic criterion. More recently, it has been suggested that arousal and desire be combined into one disorder for the upcoming DSM-V. Causes of low desire include chronic medical conditions, medications, surgeries, and psychosocial factors, but not necessarily increased age; both pre- and postmenopausal women can have HSDD, although the frequency appears to vary by age. Sexual function requires the complex interaction of multiple neurotransmitters and hormones, both centrally and peripherally, and sexual desire is considered the result of a complex balance between inhibitory and excitatory pathways in the brain. For example, dopamine, estrogen, progesterone, and testosterone play an excitatory role, whereas serotonin and prolactin are inhibitory. Thus, decreased sexual desire could be due to a reduced level of excitatory activity, an increased level of inhibitory activity, or both. A number of validated self-report and clinician-administered instruments are available for assessing female sexual function; however, most have been used primarily in clinical research trials. The Decreased Sexual Desire Screener (DSDS) was developed for practicing clinicians who are neither trained nor specialized in FSD to assist in making an accurate diagnosis of generalized acquired HSDD. As our understanding of the pathophysiology of HSDD increases, it may become easier for physicians to identify and treat women with low sexual desire.

Incorporating emotions specific to the sexual response into theories of emotion using the Indiana Sexual and Affective Word Set

The sexual response includes an emotional component, but it is not clear whether this component is specific to sex and whether it is best explained by dimensional or discrete emotion theories. To determine whether the emotional component of the sexual response is distinct from other emotions, participants (n = 1099) rated 1450 sexual and non-sexual words according to dimensional theories of emotion (using scales of valence, arousal, and dominance) and according to theories of basic emotion (using scales of happiness, anger, sadness, fear, and disgust). In addition, ratings were provided for newly developed scales of sexual valence, arousal, and energy. A factor analysis produced four factors, together accounting for 91.5% of the variance in participant ratings. Using logistic regression analysis, we found that one word category or factor, labeled "sexual," was predicted only by the new sexual arousal and energy scales. The remaining three factors, labeled "disgusting," "happy," and "basic aversive" were best predicted by basic (or discrete) emotion ratings. Dimensional ratings of valence, sexual valence, and arousal were not predictive of any of the four categories. These results suggest that the addition of sexually specific emotions to basic emotion theories is justified and needed to account fully for emotional responses to sexual stimuli. In addition, the findings provide initial validation for the Indiana Sexual and Affective Words Set (ISAWS), supporting its use in future studies.

Agreement of self-reported and genital measures of sexual arousal in men and women: a meta-analysis

The assessment of sexual arousal in men and women informs theoretical studies of human sexuality and provides a method to assess and evaluate the treatment of sexual dysfunctions and paraphilias. Understanding measures of arousal is, therefore, paramount to further theoretical and practical advances in the study of human sexuality. In this meta-analysis, we review research to quantify the extent of agreement between self-reported and genital measures of sexual arousal, to determine if there is a gender difference in this agreement, and to identify theoretical and methodological moderators of subjective-genital agreement. We identified 132 peer- or academically-reviewed laboratory studies published between 1969 and 2007 reporting a correlation between self-reported and genital measures of sexual arousal, with total sample sizes of 2,505 women and 1,918 men. There was a statistically significant gender difference in the agreement between self-reported and genital measures, with men (r = .66) showing a greater degree of agreement than women (r = .26). Two methodological moderators of the gender difference in subjective-genital agreement were identified: stimulus variability and timing of the assessment of self-reported sexual arousal. The results have implications for assessment of sexual arousal, the nature of gender differences in sexual arousal, and models of sexual response.

Brain activation evoked by erotic films varies with different menstrual phases: an fMRI study

In humans, fluctuating hormone levels throughout the menstrual cycle are believed to regulate many cyclical sexual behaviors and motivational processes. However, there is a dearth of research investigating the neural correlates of this phenomenon. We used functional magnetic resonance imaging to identify brain regions involved in sexual arousal's regulatory process. Fifteen female participants were scanned while viewing erotic film excerpts at three time points during a single menstrual cycle: ovulation, menstruation, and at one additional time point. Tripled two-group differences analysis revealed that significant activation in the comparison was observed in non-ovulatory phases of the menstrual cycle in parts of the right inferior frontal gyrus, right lateral occipital cortex, and left postcentral gyrus, as well as in the bilateral superior parietal lobule. Thus, our results indicate that brain activity differs in the ovulatory phase of the menstrual cycle compared to during other menstrual phases. This finding provides neurological evidence for the ovulatory cycle's modulation of the processing of the sexual arousal in female human brain.

Preceding attention and the dorsomedial prefrontal cortex: process specificity versus domain dependence

The dorsomedial prefrontal cortex (DMPFC) has been shown to be involved in attending different states, all including a strong emotional component. It remains unclear, though, whether neural activity in the DMPFC is predominantly determined by either a particular domain, as emotional stimuli, or by a specific process, as attention. Here, we used functional magnetic resonance imaging to test the alternative hypotheses of domain- versus process-specificity in DMPFC. Subjects had to perceive pictures from three different domains, sexual, emotional, and neutral stimuli, in both a nonattended, i.e., unexpected, and attended, i.e., expected mode. Our results show DMPFC activation during attended, i.e., expected stimulus perception when compared with nonattended, i.e., unexpected stimuli perception. DMPFC activation and corresponding behavioral changes (reaction time, subjective ratings) were observed in all three domains, sexual, emotional, and neutral stimuli. As opposed to those process-specific effects that were found predominantly in posterior DMPFC, a process by domain interaction was found to be characteristic for more anterior parts of the DMPFC. Taken together, our findings favour the hypothesis that neural activity in the posterior DMPFC is determined by a specific process, i.e., attending stimuli, and thus characterized by process-specificity rather than by a particular domain, i.e., sexual, emotional, or neutral stimuli, reflecting domain-specificity. This suggests that the anterior and posterior DMPFC is involved in the process of attending mental states while remaining more (posterior DMPFC) or less (anterior DMPFC) independent of the type or domain of the respective stimulus.

Physiologic measures of sexual function in women: a review

OBJECTIVE

To review and describe physiologic measures of assessing sexual function in women.

DESIGN

Literature review.

SETTING

Studies that use instruments designed to measure female sexual function.

PATIENT(S)

Women participating in studies of female sexual function.

INTERVENTION(S)

Various instruments that measure physiologic features of female sexual function.

MAIN OUTCOME MEASURE(S)

Appraisal of the various instruments, including their advantages and disadvantages.

RESULT(S)

Many unique physiologic methods of evaluating female sexual function have been developed during the past four decades. Each method has its benefits and limitations.

CONCLUSION(S)

Many physiologic methods exist, but most are not well-validated. In addition there has been an inability to correlate most physiologic measures with subjective measures of sexual arousal. Furthermore, given the complex nature of the sexual response in women, physiologic measures should be considered in context of other data, including the history, physical examination, and validated questionnaires. Nonetheless, the existence of appropriate physiologic measures is vital to our understanding of female sexual function and dysfunction.

Patterns of brain activation during visually evoked sexual arousal differ between homosexual and heterosexual men

BACKGROUND AND PURPOSE

Nowadays the mechanism of homosexuality is little known. Few studies have been carried out to explore the brain functional changes of homosexual men during sexual arousal. We used functional MR imaging (fMRI) to determine whether the patterns of brain activation in homosexual and heterosexual men differed during visually evoked sexual arousal.

MATERIALS AND METHODS

To all the subjects (10 homosexual and 10 heterosexual), real-time visual stimulation was provided by 3-minute exposure to 3 types of erotic film: heterosexual couples (F-M), male homosexual couples (M-M), and female homosexual couples (F-F) engaged in sexual activity, during which time fMRI was used to determine the patterns of brain activation. Self-reports of level of sexual arousal were collected immediately afterward.

RESULTS

Statistical parametric mapping showed that viewing erotic film excerpts that induced sexual arousal was associated, in both groups, with activation of the middle prefrontal gyrus, bilateral temporal lobe and postcentral gyrus, thalamus, insula, vermis, left precuneus, occipital cortex, parietal cortex, and cerebellum. In homosexual men, the left angular gyrus, left caudate nucleus, and right pallidum were activated; in contrast, heterosexual men showed no activation in these regions. However, heterosexual men showed activation in the bilateral lingual gyrus, right hippocampus, and right parahippocampal gyrus, areas not activated in homosexual men. In both groups, region-of-interest analysis revealed no correlation between the magnitude of amygdala or thalamus activation and the reported level of sexual arousal.

CONCLUSION

Our findings indicate that different neural circuits are active during sexual arousal in homosexual and heterosexual men and may contribute to a better understanding of the neural basis of male sexual orientation.

Brain response to visual sexual stimuli in heterosexual and homosexual males

Although heterosexual and homosexual individuals clearly show differences in subjective response to heterosexual and homosexual sexual stimuli, the neurobiological processes underlying sexual orientation are largely unknown. We addressed the question whether the expected differences in subjective response to visual heterosexual and homosexual stimuli may be reflected in differences in brain activation pattern. Twenty-four healthy male volunteers, 12 heterosexuals and 12 homosexuals, were included in the study. BOLD signal was measured while subjects were viewing erotic videos of heterosexual and homosexual content. SPM02 was used for data analysis. Individual sexual arousal was assessed by subjective rating. As compared to viewing sexually neutral videos, viewing erotic videos led to a brain activation pattern characteristic for sexual arousal in both groups only when subjects were viewing videos of their respective sexual orientation. Particularly, activation in the hypothalamus, a key brain area in sexual function, was correlated with sexual arousal. Conversely, when viewing videos opposite to their sexual orientation both groups showed absent hypothalamic activation. Moreover, the activation pattern found in both groups suggests that stimuli of opposite sexual orientation triggered intense autonomic response and may be perceived, at least to some extent, as aversive.