Brain processing of audiovisual sexual stimuli inducing penile erection: a positron emission tomography study

Convergent and Divergent Structural Connectivity of Brain White Matter Network Between Patients With Erectile Dysfunction and Premature Ejaculation: A Graph Theory Analysis Study

Background

Sexual dysfunction, namely, erectile dysfunction (ED) and premature ejaculation (PE), has been found to be associated with abnormal structural connectivity in the brain. Previous studies have mainly focused on a single disorder, however, convergent and divergent structural connectivity patterns of the brain network between ED and PE remain poorly understood.

Methods

T1-weighted structural data and diffusion tensor imaging data of 28 patients with psychological ED, 28 patients with lifelong PE (LPE), and 28 healthy controls (HCs) were obtained to map the white matter (WM) brain networks. Then, the graph-theoretical method was applied to investigate the differences of network properties (small-world measures) of the WM network between patients with ED and LPE. Furthermore, nodal segregative and integrative parameters (nodal clustering coefficient and characteristic path length) were also explored between these patients.

Results

Small-world architecture of the brain networks were identified for both psychological ED and LPE groups. However, patients with ED exhibited increased average characteristic path length of the brain network when compared with patients with LPE and HCs. No significant difference was found in the average characteristic path length between patients with LPE and HCs. Moreover, increased nodal characteristic path length was found in the right middle frontal gyrus (orbital part) of patients with ED and LPE when compared with HCs. In addition, patients with ED had increased nodal characteristic path length in the right middle frontal gyrus (orbital part) when compared with patients with LPE.

Conclusion

Together, our results demonstrated that decreased integration of the right middle frontal gyrus (orbital part) might be a convergent neuropathological basis for both psychological ED and LPE. In addition, patients with ED also exhibited decreased integration in the whole WM brain network, which was not found in patients with LPE. Therefore, altered integration of the whole brain network might be the divergent structural connectivity patterns for psychological ED and LPE.

Brain activations associated with anticipation and delivery of monetary reward: A systematic review and meta-analysis of fMRI studies

BACKGROUND

While multiple studies have examined the brain functional correlates of reward, meta-analyses have either focused on studies using the monetary incentive delay (MID) task, or have adopted a broad strategy, combining data from studies using both monetary and non-monetary reward, as probed using a wide range of tasks.

OBJECTIVE

To meta-analyze fMRI studies that used monetary reward and in which there was a definable cue-reward contingency. Studies were limited to those using monetary reward in order to avoid potential heterogeneity from use of other rewards, especially social rewards. Studies using gambling or delay discounting tasks were excluded on the grounds that reward anticipation is not easily quantifiable.

STUDY ELIGIBILITY

English-language fMRI studies (i) that reported fMRI findings on healthy adults; (ii) that used monetary reward; and (iii) in which a cue that was predictive of reward was compared to a no win (or lesser win) condition. Only voxel-based studies were included; those where brain coverage was incomplete were excluded.

DATA SOURCES

Ovid, Medline and PsycInfo, from 2000 to 2020, plus checking of review articles and meta-analyses.

DATA SYNTHESIS

Data were pooled using Seed-based d Mapping with Permutation of Subject Images (SDM-PSI). Heterogeneity among studies was examined using the I2 statistic. Publication bias was examined using funnel plots and statistical examination of asymmetries. Moderator variables including whether the task was pre-learnt, sex distribution, amount of money won and width of smoothing kernel were examined.

RESULTS

Pooled data from 45 studies of reward anticipation revealed activations in the ventral striatum, the middle cingulate cortex/supplementary motor area and the insula. Pooled data from 28 studies of reward delivery again revealed ventral striatal activation, plus cortical activations in the anterior and posterior cingulate cortex. There was relatively little evidence of publication bias. Among moderating variables, only whether the task was pre-learnt exerted an influence.

CONCLUSIONS

According to this meta-analysis monetary reward anticipation and delivery both activate the ventral but not the dorsal striatum, and are associated with different patterns of cortical activation.

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.

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.

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.

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.

The functional neuroanatomy of male psychosexual and physiosexual arousal: a quantitative meta-analysis

Reproductive behavior is mandatory for conservation of species and mediated by a state of sexual arousal (SA), involving both complex mental processes and bodily reactions. An early neurobehavioral model of SA proposes cognitive, emotional, motivational, and autonomic components. In a comprehensive quantitative meta-analysis on previous neuroimaging findings, we provide here evidence for distinct brain networks underlying psychosexual and physiosexual arousal. Psychosexual (i.e., mental sexual) arousal recruits brain areas crucial for cognitive evaluation, top-down modulation of attention and exteroceptive sensory processing, relevance detection and affective evaluation, as well as regions implicated in the representation of urges and in triggering autonomic processes. In contrast, physiosexual (i.e., physiological sexual) arousal is mediated by regions responsible for regulation and monitoring of initiated autonomic processes and emotions and for somatosensory processing. These circuits are interconnected by subcortical structures (putamen and claustrum) that provide exchange of sensorimotor information and crossmodal processing between and within the networks. Brain deactivations may imply attenuation of introspective processes and social cognition, but be necessary to release intrinsic inhibition of SA.

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.

Bladder, bowel, and sexual dysfunction in Parkinson's disease

Bladder dysfunction (urinary urgency/frequency), bowel dysfunction (constipation), and sexual dysfunction (erectile dysfunction) (also called “pelvic organ” dysfunctions) are common nonmotor disorders in Parkinson's disease (PD). In contrast to motor disorders, pelvic organ autonomic dysfunctions are often nonresponsive to levodopa treatment. The brain pathology causing the bladder dysfunction (appearance of overactivity) involves an altered dopamine-basal ganglia circuit, which normally suppresses the micturition reflex. By contrast, peripheral myenteric pathology causing slowed colonic transit (loss of rectal contractions) and central pathology causing weak strain and paradoxical anal sphincter contraction on defecation (PSD, also called as anismus) are responsible for the bowel dysfunction. In addition, hypothalamic dysfunction is mostly responsible for the sexual dysfunction (decrease in libido and erection) in PD, via altered dopamine-oxytocin pathways, which normally promote libido and erection. The pathophysiology of the pelvic organ dysfunction in PD differs from that in multiple system atrophy; therefore, it might aid in differential diagnosis. Anticholinergic agents are used to treat bladder dysfunction in PD, although these drugs should be used with caution particularly in elderly patients who have cognitive decline. Dietary fibers, laxatives, and “prokinetic” drugs such as serotonergic agonists are used to treat bowel dysfunction in PD. Phosphodiesterase inhibitors are used to treat sexual dysfunction in PD. These treatments might be beneficial in maximizing the patients' quality of life.

A dual physiological character for sexual function: libido and sexual pheromones

Human sexual response is a complex function involving many cerebral, spinal and peripheral aspects; the last are relatively known and benefit from good pharmacological control, as in the case of erectile dysfunction. Spinal cord sexual reflexes also have a good theoretical and experimental description. There is minimal understanding of the cerebral sexual processes (libido, sexual arousal, orgasm). The initial perspective was that the cerebral areas implied in sexuality exert descending stimulatory and inhibitory influences on spinal cord sexual centres/reflexes. This was a wrong supposition, which inhibited progress in this subject, with a considerable impact on a subject's individual and social life. A new approach to sexual function arises from the idea that simple neurological structures can support only simple functions, while a more complex function requires correspondingly complex anatomical structures. For this reason the spinal cord would not be able to realise the integration of multiple (spinal and psychosensorial) stimuli into a unique and coherent ejaculation response. Consequently, all mechanisms implied in human sexuality would be cerebral processes, ejaculation reflexes ascending in evolution to the cerebral level. This new evolutionary concept was developed after 2001 in five distinct articles on the cerebral duality of sexual arousal, sexual hormones, ejaculation and serotonergic receptors. During this period other published results suggested a possible cerebral duality for sexual pheromones and libido in humans. All these dual physiological aspects are integrated in this review into one neurophysiological model, thus trying to further develop the new concepts of sexual function and perhaps relational behaviour. In conclusion, ejaculation is a dual cerebral process with arousal sensation (hormonally modulated) and libido perception (pheromonally modulated) as the afferent part. Two neurophysiological axes could exist in both men and women. In this assumption the mechanisms for libido and sexual arousal are not the only ones invoked, their correlations and implications are also suggested, perhaps critical aspects for further developments in the field.

Sex differences in visual attention to sexually explicit videos: a preliminary study

INTRODUCTION

Although men appear to be more interested in sexual stimuli than women, this difference is not completely understood. Eye-tracking technology has been used to investigate visual attention to still sexual images; however, it has not been applied to moving sexual images.

AIM

To investigate whether sex difference exists in visual attention to sexual videos.

METHODS

Eleven male and 11 female healthy volunteers were studied by our new methodology.

MAIN OUTCOME MEASURES

The subjects viewed two sexual videos (one depicting sexual intercourse and one not) in which several regions were designated for eye-gaze analysis in each frame. Visual attention was measured across each designated region according to gaze duration. Sex differences, the region attracting the most attention, and visually favored sex were evaluated.

RESULTS

In the nonintercourse clip, gaze time for the face and body of the actress was significantly shorter among women than among men. Gaze time for the face and body of the actor and nonhuman regions was significantly longer for women than men. The region attracting the most attention was the face of the actress for both men and women. Men viewed the opposite sex for a significantly longer period than did women, and women viewed their own sex for a significantly longer period than did men. However, gaze times for the clip showing intercourse were not significantly different between sexes.

CONCLUSIONS

A sex difference existed in visual attention to a sexual video without heterosexual intercourse; men viewed the opposite sex for longer periods than did women, and women viewed the same sex for longer periods than did men. There was no statistically significant sex difference in viewing patterns in a sexual video showing heterosexual intercourse, and we speculate that men and women may have similar visual attention patterns if the sexual stimuli are sufficiently explicit.

Fos expression at the cerebellum following non-contact arousal and mating behavior in male rats

The cerebellum is considered a center underlying fine movements, cognition, memory and sexual responses. The latter feature led us to correlate sexual arousal and copulation in male rats with neural activity at the cerebellar cortex. Two behavioral paradigms were used in this investigation: the stimulation of males by distant receptive females (non-contact sexual stimulation), and the execution of up to three consecutive ejaculations. The vermis area of the cerebellum was removed following behavioral experiments, cut into sagittal sections, and analyzed with Fos immunohistochemistry to determine neuronal activation. At the mid-vermis region (sections from the midline to 0.1 mm laterally), non-contact stimulation significantly increased the activity of granule neurons. The number of activated cells increased in every lobule, but lobules 1 and 6 to 9 showed the greatest increment. In sexual behavior tests, males reaching one ejaculation had a high number of activated neurons similar to those counted after non-contact stimulation. However, two or three consecutive ejaculations showed a smaller number of Fos-ir cells. In contrast to the mid-vermis region, sections farthest from the midline (0.1 to 0.9 mm laterally) revealed that only lobule 7 expressed activated neurons. These data suggest that a well-delineated group of granule neurons have a sexual biphasic response at the cerebellar vermis, and that Fos in them is under an active degradation mechanism. Thus, they participate as a neural substrate for male rat sexual responses with an activation-deactivation process corresponding with the sensory stimulation and motor performance occurring during copulation.

Differential brain processing of audiovisual sexual stimuli in men: Comparative positron emission tomography study of the initiation and maintenance of penile erection during sexual arousal

The human male psychosexual cycle consists of four phases: excitation, plateau, orgasm, and resolution. Identification of the specific neural substrates of each phase may provide information regarding the brain's pathophysiology of sexual dysfunction. We previously analyzed regional cerebral blood flow (rCBF) with H(2)15O-positron emission tomography (PET) during the excitation phase (initiation of penile erection) induced by audiovisual sexual stimuli (AVSS) and identified activation of the cerebellar vermis, the bilateral extrastriate cortex, and right orbitofrontal cortex, suggesting a role of cognition/emotion in the excitement phase. In the present study, we analyzed rCBF of the same six healthy volunteers during the plateau phase (maintenance of penile erection) induced by AVSS and compared the results with those of the excitation phase. Penile rigidity was monitored in real time with RigiScan Plus during PET scanning. Images were analyzed by statistical parametric mapping (SPM) software, and rCBF in the amygdala, hypothalamus, anterior cingulate, and insula was measured. During the plateau phase, primary subcortical activation was noted in the right ventral putamen, indicating motivational factors in the sexual response via the limbic reward circuit. A significant increase in rCBF in the left hypothalamus was also observed during the plateau phase. The right anterior cingulate and left insula were specifically activated during the excitation phase but not during the plateau phase. These results indicate a significant role of the ventral putamen and the hypothalamus in the plateau phase and confirm that paralimbic and limbic components of the human brain differentially coordinate the sexual response in a psychosexual phase-dependent manner.