The neural basis of sex differences in sexual behavior: A quantitative meta-analysis

Topological differences of striato-thalamo-cortical circuit in functional brain network between premature ejaculation patients with and without depression

INTRODUCTION

Premature ejaculation (PE), a common male sexual dysfunction, often accompanies by abnormal psychological factors, such as depression. Recent neuroimaging studies have revealed structural and functional brain abnormalities in PE patients. However, there is limited neurological evidence supporting the comorbidity of PE and depression. This study aimed to explore the topological changes of the functional brain networks of PE patients with depression.

METHODS

Resting-state functional magnetic resonance imaging (rs-fMRI) data were acquired from 60 PE patients (30 with depression and 30 without depression) and 29 healthy controls (HCs). Functional brain networks were constructed for all participants based on rs-fMRI data. The nodal parameters including nodal centrality and efficiency were calculated by the method of graph theory analysis and then compared between groups. In addition, the results were corrected for multiple comparisons by family-wise error (FWE) (p < .05).

RESULTS

PE patients with depression had increased degree centrality and global efficiency in the right pallidum, as well as increased degree centrality in the right thalamus when compared with HCs. PE patients without depression showed increased degree centrality in the right pallidum and thalamus, as well as increased global efficiency in the right precuneus, pallidum, and thalamus when compared with HCs. PE patients with depression demonstrated decreased degree centrality in the right pallidum and thalamus, as well as decreased global efficiency in the right precuneus, pallidum, and thalamus when compared to those without depression. All the brain regions above survived the FWE correction.

CONCLUSION

The results suggested that increased and decreased functional connectivity, as well as the capability of global integration of information in the brain, might be related to the occurrence of PE and the comorbidity depression in PE patients, respectively. These findings provided new insights into the understanding of the pathological mechanisms underlying PE and those with depression.

Women and men with distressing low sexual desire exhibit sexually dimorphic brain processing

Distressing low sexual desire, termed Hypoactive Sexual Desire Disorder (HSDD), affects approximately 10% of women and 8% of men. In women, the 'top-down' theory of HSDD describes hyperactivity in higher-level cognitive brain regions, suppressing lower-level emotional/sexual brain areas. However, it is unknown how this neurofunctional disturbance compares to HSDD in men. To investigate this, we employed task-based functional MRI in 32 women and 32 men with HSDD to measure sexual-brain processing during sexual versus non-sexual videos, as well as psychometric questionnaires to assess sexual desire/arousal. We demonstrate that women had greater activation in higher-level and lower-level brain regions, compared to men. Indeed, women who had greater hypothalamic activation in response to sexual videos, reported higher psychometric scores in the evaluative (r = 0.55, P = 0.001), motivational (r = 0.56, P = 0.003), and physiological (r = 0.57, P = 0.0006) domains of sexual desire and arousal after watching the sexual videos in the scanner. By contrast, no similar correlations were observed in men. Taken together, this is the first direct comparison of the neural correlates of distressing low sexual desire between women and men. The data supports the 'top-down' theory of HSDD in women, whereas in men HSDD appears to be associated with different neurofunctional processes.

Sleep dysfunction mediates the relationship between hypothalamic-insula connectivity and anxiety-depression symptom severity bidirectionally in young adults

BACKGROUND

The hypothalamus plays a crucial role in regulating sleep-wake cycle and motivated behavior. Sleep disturbance is associated with impairment in cognitive and affective functions. However, how hypothalamic dysfunction may contribute to inter-related sleep, cognitive, and emotional deficits remain unclear.

METHODS

We curated the Human Connectome Project dataset and investigated how hypothalamic resting state functional connectivities (rsFC) were associated with sleep dysfunction, as evaluated by the Pittsburgh Sleep Quality Index (PSQI), cognitive performance, and subjective mood states in 687 young adults (342 women). Imaging data were processed with published routines and evaluated with a corrected threshold. We examined the inter-relationship amongst hypothalamic rsFC, PSQI score, and clinical measures with mediation analyses.

RESULTS

In whole-brain regressions with age and drinking severity as covariates, men showed higher hypothalamic rsFC with the right insula in correlation with PSQI score. No clusters were identified in women at the same threshold. Both hypothalamic-insula rsFC and PSQI score were significantly correlated with anxiety and depression scores in men. Further, mediation analyses showed that PSQI score mediated the relationship between hypothalamic-insula rsFC and anxiety/depression symptom severity bidirectionally in men.

CONCLUSIONS

Sleep dysfunction is associated with negative emotions and hypothalamic rsFC with the right insula, a core structure of the interoceptive circuits. Notably, anxiety-depression symptom severity and altered hypothalamic-insula rsFC are related bidirectionally by poor sleep quality. These findings are specific to men, suggesting potential sex differences in the neural circuits regulating sleep and emotional states that need to be further investigated.

Effect of prefrontal transcranial direct current stimulation on sexual arousal: A proof of concept study

There is preliminary evidence that high-frequency repetitive transcranial magnetic stimulation targeting the right dorsolateral prefrontal cortex (DLPFC) could reduce cue-induced sexual arousal. Here, we aimed to replicate this finding by using transcranial direct current stimulation (tDCS). In a randomized, double-blind, sham-controlled crossover study design, 24 healthy male participants received anodal tDCS over right DLPFC, anodal tDCS over left DLPFC, and sham tDCS with exposure to neutral and sexual video cues before and after each intervention. None of the interventions significantly reduced subjective sexual arousal. Stimulation parameters should be varied in further studies to identify factors relevant to the intended effect.

Pattern recognition reveals sex-dependent neural substrates of sexual perception

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

Descriptive Study of Gender Dysphoria and Sexual Behavior in a Disorder of Sex Development Group

Disorder of Sex Development (DSD) refers to a heterogeneous group of congenital conditions in which chromosomal, gonadal, and anatomical sex are atypical. Typically, the diagnosis is made at birth or infancy and interventional actions are necessary in many cases. The repercussions in adult life, more specifically in the field of sexuality, have not been not widely studied yet. This study shows research data that seek to identify in a group of individuals with DSD (XX DSD, XY DSD, Chromosomal DSD), who are being monitored in the departments of pediatric surgery and urology of a hospital in the period from 2000 to 2019, and to verify the consequences on sex life after puberty. The sample has 16 participants (7 XY DSD, 4 XX DSD, and 5 Chromosomal DSD), aged between 16 and 50 years, single, with high school education, residents of the state capital and countryside of the state. The results depict the presence of a case of Gender Dysphoria; postponement of sexual debut for almost 3 years compared to the national average; a single sexual relationship for those who have already had a sexual experience with penetration; penis size below the general population average; presence of masturbatory activity in most participants. The presence of sexual attraction and masturbation indicate sexual desire. The group has a late onset of sexual life (almost 3 years after the national average). A recurrent feature in this group is that, even having already performed a penetrative sexual act, there is no continuation in their sexual life. The main noticeable aspect about Gender Dysphoria is the presence of only one case of incongruence in the Chromosomal DSD group. The limited sample prevents us from sufficient statements for generalization.

Hearing, touching, and multisensory integration during mate choice

Mate choice is a potent generator of diversity and a fundamental pillar for sexual selection and evolution. Mate choice is a multistage affair, where complex sensory information and elaborate actions are used to identify, scrutinize, and evaluate potential mating partners. While widely accepted that communication during mate assessment relies on multimodal cues, most studies investigating the mechanisms controlling this fundamental behavior have restricted their focus to the dominant sensory modality used by the species under examination, such as vision in humans and smell in rodents. However, despite their undeniable importance for the initial recognition, attraction, and approach towards a potential mate, other modalities gain relevance as the interaction progresses, amongst which are touch and audition. In this review, we will: (1) focus on recent findings of how touch and audition can contribute to the evaluation and choice of mating partners, and (2) outline our current knowledge regarding the neuronal circuits processing touch and audition (amongst others) in the context of mate choice and ask (3) how these neural circuits are connected to areas that have been studied in the light of multisensory integration.

Insights into the role of pERK1/2 signaling in post-cerebral ischemia reperfusion sexual dysfunction in rats

The purpose of the present study was to investigate the effects of ERK1/2 inhibition on both the amygdala and hippocampal structures, and to investigate its role in regulating memory for sexual information. This study utilized a cerebral ischemia reperfusion (IR) model to produce a stressful brain condition that highlights the possible involvement of a hippocampal GC/pERK1/2/BDNF pathway in the resulting sexual consequences of this ailment. Male Wistar rats were divided into four groups: (1) sham; (2) IR: subjected to 45 min of ischemia followed by 48 h of reperfusion; (3) PD98059: received PD98059 at 0.3 mg/kg, i.p.; (4) IR + PD98059. This study provides new evidence for cerebral IR-induced amygdala injury and the sexual impairments that are associated with motor and cognitive deficits in rats. These findings were correlated with histopathological changes that are defined by extensive neuronal loss in both the hippocampus and the amygdala. The current study postulated that the ERK inhibitor PD98059 could reverse IR-induced injury in the amygdala as well as reversing IR-induced sexual impairments. This hypothesis is supported by the ability of PD98059 to: (1) restore luteinizing hormone and testosterone levels; (2) increase sexual arousal and copulatory performance (as evidenced by modulating mount, intromission, ejaculation latencies, and post-ejaculatory intervals); (3) improve the histological profile in the amygdala that is associated with reduced glutamate levels, c-Fos expression, and elevated gamma aminobutyric acid levels. In conclusion, the present findings introduce pERK1/2 inhibition as a possible strategy for enhancing sexual activity in survivors of IR.

Distended Seminal Vesicles Are Involved in Specific Cerebral Sexual Arousal: A Pilot Study Using Functional Brain Imaging in Young Healthy Men

Background

Objective

Design, setting, and participants

Outcome measurements and statistical analysis

Results and limitations

Conclusions

Patient summary

Effects of sex hormones on brain GABA and glutamate levels in a cis- and transgender cohort

Sex hormones affect the GABAergic and glutamatergic neurotransmitter system as demonstrated in animal studies. However, human research has mostly been correlational in nature. Here, we aimed at substantiating causal interpretations of the interaction between sex hormones and neurotransmitter function by using magnetic resonance spectroscopy imaging (MRSI) to study the effect of gender-affirming hormone treatment (GHT) in transgender individuals. Fifteen trans men (TM) with a DSM-5 diagnosis of gender dysphoria, undergoing GHT, and 15 age-matched cisgender women (CW), receiving no therapy, underwent MRSI before and after at least 12 weeks. Additionally, sex differences in neurotransmitter levels were evaluated in an independent sample of 80 cisgender men and 79 cisgender women. Mean GABA+ (combination of GABA and macromolecules) and Glx (combination of glutamate and glutamine) ratios to total creatine (GABA+/tCr, Glx/tCr) were calculated in five predefined regions-of-interest (hippocampus, insula, pallidum, putamen and thalamus). Linear mixed models analysis revealed a significant measurement by gender identity effect (p_corr. = 0.048) for GABA+/tCr ratios in the hippocampus, with the TM cohort showing decreased GABA+/tCr levels after GHT compared to CW. Moreover, analysis of covariance showed a significant sex difference in insula GABA+/tCr ratios (p_corr. = 0.049), indicating elevated GABA levels in cisgender women compared to cisgender men. Our study demonstrates GHT treatment-induced GABA+/tCr reductions in the hippocampus, indicating hormone receptor activation on GABAergic cells and testosterone-induced neuroplastic processes within the hippocampus. Moreover, elevated GABA levels in the female compared to the male insula highlight the importance of including sex as factor in future MRS studies. DATA AVAILABILITY STATEMENT: Due to data protection laws processed data is available from the authors upon reasonable request. Please contact rupert.lanzenberger@meduniwien.ac.at with any questions or requests.

The Empirical Status of the Preparation Hypothesis: Explicating Women's Genital Responses to Sexual Stimuli in the Laboratory

Research conducted in our laboratory and in other laboratories has revealed that (1) women's genital responses to visual and auditory stimuli are strongly affected by the presence of sexual cues, but that (2) specific sexual cues (e.g., gender of actors, the presence of sexual violence) often have little impact on the magnitude of the responses-that is, similar genital responses are observed to very different sexual stimuli. In addition, (3) women's genital responses do not strongly correspond with self-reported sexual partner and activity preferences, or (4) with self-reported sexual arousal during the presentation of sexual stimuli. Taken together, these facts represent a puzzle, especially considering that men's genital responses are highly affected by specific sexual cues and strongly correspond to stated preferences and self-reported sexual arousal. One hypothesis to explain female low cue-specificity and low concordance (relative to men) is the preparation hypothesis: Women's indiscriminate genital responses serve a protective function. That is, they do not indicate or necessarily promote sexual interest and motivation, but rather prepare the vaginal lumen for possible sexual activity and therefore prevent injuries that may occur as a result of penetration. We review evidence for and against this hypothesis. We conclude that the evidence is favorable but not entirely convincing, and more work is required to reach a firm conclusion. We offer directions for future research.

The Brain Activation-Based Sexual Image Classifier (BASIC): A Sensitive and Specific fMRI Activity Pattern for Sexual Image Processing

Previous studies suggest there is a complex relationship between sexual and general affective stimulus processing, which varies across individuals and situations. We examined whether sexual and general affective processing can be distinguished at the brain level. In addition, we explored to what degree possible distinctions are generalizable across individuals and different types of sexual stimuli, and whether they are limited to the engagement of lower-level processes, such as the detection of visual features. Data on sexual images, nonsexual positive and negative images, and neutral images from Wehrum et al. (2013) (N = 100) were reanalyzed using multivariate support vector machine models to create the brain activation-based sexual image classifier (BASIC) model. This model was tested for sensitivity, specificity, and generalizability in cross-validation (N = 100) and an independent test cohort (N = 18; Kragel et al. 2019). The BASIC model showed highly accurate performance (94–100%) in classifying sexual versus neutral or nonsexual affective images in both datasets with forced choice tests. Virtual lesions and tests of individual large-scale networks (e.g., visual or attention networks) show that individual networks are neither necessary nor sufficient to classify sexual versus nonsexual stimulus processing. Thus, responses to sexual images are distributed across brain systems.

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.

Sexual incentive delay in the scanner: Sexual cue and reward processing, and links to problematic porn consumption and sexual motivation

BACKGROUND AND AIMS

The use of pornography, while unproblematic for the majority, can grow into addiction-like behavior which in its extreme form is labeled as compulsive sexual behavioral disorder in the ICD-11 (WHO, 2018). The aim of this study was to investigate the addiction-specific reactivity to cues in order to better understand underlying mechanisms in the development of this disorder.

METHODS

We have used an optimized Sexual Incentive Delay Task to study brain activity in reward associated brain areas during an anticipation phase (with cues predicting pornographic videos, control videos or no videos) and a corresponding delivery phase in healthy men. Correlations to indicators of problematic pornography use, the time spent on pornography use, and trait sexual motivation were analyzed.

RESULTS

The results of 74 men showed that reward-related brain areas (amygdala, dorsal cingulate cortex, orbitofrontal cortex, nucleus accumbens, thalamus, putamen, caudate nucleus, and insula) were significantly more activated by both the pornographic videos and the pornographic cues than by control videos and control cues, respectively. However, we found no relationship between these activations and indicators of problematic pornography use, time spent on pornography use, or with trait sexual motivation.

DISCUSSION AND CONCLUSIONS

The activity in reward-related brain areas to both visual sexual stimuli as well as cues indicates that optimization of the Sexual Incentive Delay Task was successful. Presumably, associations between reward-related brain activity and indicators for problematic or pathological pornography use might only occur in samples with increased levels and not in a rather healthy sample used in the present study.

Sex differences in neural responses to reward and the influences of individual reward and punishment sensitivity

BACKGROUND

Men and women show differences in sensitivity to reward and punishment, which may impact behavior in health and disease. However, the neural bases of these sex differences remain under-investigated. Here, by combining functional magnetic resonance imaging (fMRI) and a variant of the Monetary Incentive Delay Task (MIDT), we examined sex differences in the neural responses to wins and losses and how individual reward and punishment sensitivity modulates these regional activities.

METHODS

Thirty-sex men and 27 women participated in the fMRI study. We assessed sensitivity to punishment (SP) and sensitivity to reward (SR) with the Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSRQ). In the MIDT, participants pressed a button to collect reward ($1, 1¢, or nil), with the reaction time window titrated across trials so participants achieved a success rate of approximately 67%. We processed the Imaging data with published routines and evaluated the results with a corrected threshold.

RESULTS

Women showed higher SP score than men and men showed higher SR score than women. Men relative to women showed higher response to the receipt of dollar or cent reward in bilateral orbitofrontal and visual cortex. Men as compared to women also showed higher response to dollar loss in bilateral orbitofrontal cortex. Further, in whole-brain regressions, women relative to men demonstrated more significant modulation by SP in the neural responses to wins and larger wins, and the sex differences were confirmed by slope tests.

CONCLUSIONS

Together, men showed higher SR and neural sensitivity to both wins, large or small, and losses than women. Individual differences in SP were associated with diminished neural responses to wins and larger wins in women only. These findings highlight how men and women may differ in reward-related brain activations in the MIDT and add to the imaging literature of sex differences in cognitive and affective functions.

Periodontitis, erectile dysfunction, reproductive hormones, and semen quality: A systematic review

BACKGROUND

There is increasing evidence that periodontitis may affect male sexual health (MSH) (erectile function, production of sex hormones, and semen quality). However, a limited number of clinical studies demonstrate the association between MSH and periodontitis.

OBJECTIVES

The aim of this study was to explore the relationship between periodontitis and MSF.

MATERIALS AND METHODS

A comprehensive systematic review of the published literature in MEDLINE, PubMed, Scopus, Cochrane, EMBASE, and Web of Science databases from the earliest available online indexing year until October 2020 was performed, in accordance with the PRISMA guidelines. Keywords related to periodontitis were combined with words describing MSH.

RESULT

A total of 19 studies were included and discussed in the systematic review. The number of study participants ranged from 53 to 197,136 individuals, aged between 18 and 95 years (mean age, 41.2 years). Six studies did not report the age of the participants. Out of nine studies, eight found a significant association between erectile dysfunction (ED) and periodontitis. Only three studies evaluated the association between sex hormone levels and periodontitis, and two of these studies showed that patients with periodontitis are expected to exhibit higher levels of testosterone. Finally, out of five studies, two demonstrated a significant association between semen quality and periodontitis.

DISCUSSION

The findings in this review were limited by the quality and the few available studies. Results from the observational studies might have been affected by recall bias and confounded by cofactors.

CONCLUSION

The results of this systematic review revealed a significant association between periodontitis and ED, although the responsible mechanisms remain unclear. The potential associations between sex hormone levels, semen quality, and periodontitis are yet to be demonstrated. In order to improve patient management, dentists and physicians need to be aware of the association between male sexual health problems and periodontitis.

Neural and Hormonal Correlates of Sexual Arousal in Transgender Persons

BACKGROUND

Whereas mounting work has begun to document the neural correlates underlying sexual arousal (SA) in humans, the associations between gender identity and the brain correlates of SA as well as their hormonal contributions remain unknown.

AIM

This study investigated neural activation to sexual arousal in transgender and cisgender persons.

METHODS

20 transgender men and 19 transgender women (TW) already living in their identified gender were compared to 21 cisgender men (CM) and 19 cisgender women. Participants viewed erotic and neutral video clips while undergoing 3 Tesla magnetic resonance imaging.

OUTCOMES

Group-specific brain activation, brain functional connectivity, and brain-hormone associations within the neurophenomenological model of sexual arousal (Stoleru et al, 2012).

RESULTS

Consistent with the model, participants activated most of its components. However, between-group differences were mostly showing larger activation for CM relative to any of the other 3 groups. Moreover, functional connectivity analyses (psychophysiological interactions) indicated unique patterns for CM, cisgender women, and TW in how different components of SA communicated with one another. Finally, androgens in transgender men and estrogens in TW correlated negatively with parietal cortex and primary (sensori-) motor regions, respectively, while CM showed positive correlations of androgens with parietal cortex, somatosensory regions, and the insula.

CLINICAL IMPLICATIONS

Data provide information on neurobiological changes in sexual arousal during treatment with gender-affirming hormone therapy.

STRENGTHS & LIMITATIONS

Although a limitation is the lack of pretreatment data, the present study provides comprehensive information including brain activation, functional connectivity, and hormonal associations in a large sample.

CONCLUSIONS

The results highlight a complex picture of the neural correlates of SA in gender identity and sex assigned at birth. Mueller SC, Wierckx K, T'Sjoen G. Neural and Hormonal Correlates of Sexual Arousal in Transgender Persons. J Sex Med 2020;17:2495-2507.

Pharmacotherapy of Sexual Addiction

PURPOSE OF REVIEW

We reviewed recent data on sexual addiction and its treatment. We examined the different definitions of this disorder, related to the pathophysiological mechanisms. We addressed the pharmacological treatment of sexual addiction.

RECENT FINDINGS

Hypersexual behavior can be considered an addictive disorder. Sexual addiction is accompanied by significant psychiatric and addictive comorbidities and is responsible for life impairment. A comprehensive and efficient treatment must be proposed. Selective serotonin reuptake inhibitors seem the first-line pharmacological treatment for sexual addiction. Naltrexone could be another therapeutic option. Psychotherapy and preferentially cognitive-behavioral therapy should be used in association with pharmacotherapy and treatments of comorbidities.

Hypothalamic response to cocaine cues and cocaine addiction severity

The dopaminergic motive system is compromised in cocaine addiction. Abundant research has examined the roles of the dopaminergic midbrain and ventral striatum (VS) in cue-induced craving and habitual drug consumption. Interconnected with the dopaminergic circuits, the hypothalamus is widely implicated in motivated behavior, including food and drug seeking. However, very few studies have investigated how the hypothalamus responds to drug cues and whether hypothalamic responses are related to clinical features such as craving and addiction severity. Here, in 23 cocaine-dependent individuals (CD) exposed to cocaine vs neutral cues during functional magnetic resonance imaging (fMRI), we examined regional responses using established routines. At a corrected threshold, CD demonstrated increased activation to cocaine vs neutral cues in bilateral visual cortex, inferior parietal and middle frontal gyri, and the hypothalamus. The extent of hypothalamus but not other regional response was correlated with craving and cocaine addiction severity, each as assessed by the Cocaine Craving Questionnaire (CCQ) and Cocaine Selective Severity Assessment (CSSA). In contrast, subjective "acute" craving as elicited by cocaine cues during fMRI involved deactivation of bilateral orbitofrontal cortex (OFC) and angular gyri (AG), and the OFC and AG responses were not related to CCQ or CSSA score. These findings distinguished tonic craving as a critical factor in capturing cocaine addiction severity and substantiated a role of the hypothalamus in motivational dysfunction in cocaine addiction.

Hypothalamic Responses to Cocaine and Food Cues in Individuals with Cocaine Dependence

BACKGROUND

Individuals with cocaine addiction are characterized by under-responsiveness to natural reinforcers. As part of the dopaminergic pathways, the hypothalamus supports motivated behaviors. Rodent studies suggested inter-related roles of the hypothalamus in regulating drug and food intake. However, few studies have investigated hypothalamic responses to drugs and food or related cues in humans.

METHODS

We examined regional responses in 20 cocaine-dependent and 24 healthy control participants exposed to cocaine/food (cocaine dependent) and food (healthy control) vs neutral cues during functional magnetic resonance imaging. We examined the relationship between imaging findings and clinical variables and performed mediation analyses to examine the inter-relationships between cue-related activations, tonic cocaine craving, and recent cocaine use.

RESULTS

At a corrected threshold, cocaine-dependent participants demonstrated higher activation to cocaine than to food cues in the hypothalamus, inferior parietal cortex, and visual cortex. Cocaine-dependent participants as compared with healthy control participants also demonstrated higher hypothalamic activation to food cues. Further, the extent of these cue-induced hypothalamic activations was correlated with tonic craving, as assessed by the Cocaine Craving Questionnaire, and days of cocaine use in the prior month. In mediation analyses, hypothalamic activation to cocaine and food cues both completely mediated the relationship between the Cocaine Craving Questionnaire score and days of cocaine use in the past month.

CONCLUSIONS

The results were consistent with the proposition that the mechanisms of feeding and drug addiction are inter-linked in the hypothalamus and altered in cocaine addiction. The findings provide new evidence in support of hypothalamic dysfunction in cocaine addiction.

Attentional bias toward and distractibility by sexual cues: A meta-analytic integration

From an evolutionary perspective, sexual stimuli are highly salient and are assumed to be processed with high priority. Hence, attentional processing of sexual cues is expected to not only bias attention but to also distract from other cognitive (foreground) tasks. It is, however, unclear to what extent these stimuli capture attention and whether there are differences between men and women. This meta-analysis combined the results of 32 studies employing experiments of attentional bias toward and distraction by sexual stimuli. From these, 13 studies provided data to examine gender differences. Overall, attentional bias and distractibility was lower than anticipated (g_z = 0.43, p < .001) and there was support for the assumption of higher attention bias/interference in men (g_s = 0.29, p = .031). Importantly, there was evidence for the presence of publication bias. With this in mind, findings are discussed in the context of stimulus features, the impact of provoked sexual arousal and motivational state, and gender-specific and -nonspecific neural processing of sexual stimuli which influence attention toward them.

No Sex Difference Found: Cues of Sexual Stimuli Activate the Reward System in both Sexes

Sexually explicit material (SEM) is increasingly used in western societies. One reason for this high usage might be the rewarding property of SEM demonstrated in many brain imaging studies showing an activation of the reward system during the presentation of SEM. It is not yet well understood why women use SEM to a remarkably lesser extent than men. Maybe men react stronger to stimuli - so called SEM cues -, which signal the presentation of SEM and are therefore more vulnerable to use SEM than women. Therefore, the present study aimed at investigating the sex specific neural correlates towards SEM and SEM cues. We were further interested in whether person characteristics as trait sexual motivation, extent of SEM use in the last month, and age at onset of goal-oriented SEM use affect the neural responses to SEM and SEM cues. The trials of the fMRI experiment consisted of an expectation phase with SEM or neutral cues and a presentation phase with SEM or neutral stimuli, respectively. Analyses showed that the reward circuitry was activated by SEM, but also by SEM cues. There were some sex differences in hemodynamic responses to SEM during the presentation phase, but not during the expectation phase to SEM cues in any of the regions of interest. The influence of the investigated person characteristics was only small if existent. The results suggest that sex specific cue processing cannot explain sex differences in the use of SEM.

Neural substrates of sexual arousal are not sex dependent

Neuroimaging studies suggest differences in the underlying biology of sexual arousal associated with sex and sexual orientation, yet their findings are conflicting. Following a thorough statistical review of all significant neuroimaging studies, we offer strong quantitative evidence that the neuronal response to visual sexual stimuli, contrary to the widely accepted view, is independent of biological sex. Both men and women show increased activation in many cortical and subcortical brain regions thought to be involved in the response to visual sexual stimuli, while the limited sex differences that have been found and reported previously refer to subjective rating of the content.

Sexual arousal is a dynamical, highly coordinated neurophysiological process that is often induced by visual stimuli. Numerous studies have proposed that the cognitive processing stage of responding to sexual stimuli is the first stage, in which sex differences occur, and the divergence between men and women has been attributed to differences in the concerted activity of neural networks. The present comprehensive metaanalysis challenges this hypothesis and provides robust quantitative evidence that the neuronal circuitries activated by visual sexual stimuli are independent of biological sex. Sixty-one functional magnetic resonance imaging studies (1,850 individuals) that presented erotic visual stimuli to men and women of different sexual orientation were identified. Coordinate-based activation likelihood estimation was used to conduct metaanalyses. Sensitivity and clustering analyses of averaged neuronal response patterns were performed to investigate robustness of the findings. In contrast to neutral stimuli, sexual pictures and videos induce significant activations in brain regions, including insula, middle occipital, anterior cingulate and fusiform gyrus, amygdala, striatum, pulvinar, and substantia nigra. Cluster analysis suggests stimulus type as the most, and biological sex as the least, predictor for classification. Contrast analysis further shows no significant sex-specific differences within groups. Systematic review of sex differences in gray matter volume of brain regions associated with sexual arousal (3,723 adults) did not show any causal relationship between structural features and functional response to visual sexual stimuli. The neural basis of sexual arousal in humans is associated with sexual orientation yet, contrary to the widely accepted view, is not different between women and men.

Expectation of sexual images of adults and children elicits differential dorsal anterior cingulate cortex activation in pedophilic sexual offenders and healthy controls

Background

Pedophilic disorder is characterized by increased sexual interest towards children, with comparatively lesser interest towards adults. In real life, the behavior of subjects with pedophilic disorder is shaped by evaluative processes in response to sexually relevant cues. Therefore, brain activation during anticipation of sexually relevant cues is of potential interest. Whereas previous research demonstrated reduced activation when viewing adult (non-preferred) sexual stimuli in pedophilic sex offenders (PSOs), it is not known if anticipation of preferred versus unpreferred stimuli will elicit differential brain activation.

Methods

Two fMRI studies (1.5 and 7 Tesla) were conducted in separate samples, each with 26 subjects (13/13 PSOs/controls) to assess brain activity during expectancy of subsequent adult (non-preferred) sexual stimuli. In the second study (7 Tesla) additionally child (preferred) cues were presented.

Results

As predicted, expectancy of adult sexual stimuli generated smaller dorsal anterior cingulate cortex (dACC) activation in PSOs in both studies, driven by stronger activation during expectancy of adult erotic stimuli in non-pedophilic controls (HCs). In the second study, PSOs showed significantly increased activations in dACC during expectancy of child stimuli compared with expectancy of adult stimuli. This difference was significantly greater compared to the same contrast in HCs, thus demonstrating preference specificity of dACC activation.

Conclusion

Our findings support the notion of decreased brain activation to adult cues in PSOs and preference specificity in neural response during expectancy of erotic stimuli. The localization of these cue reactivity differences in the salience network supports the interpretation that PSOs show abnormally increased preparatory activation even before relevant sexual stimuli are actually presented.

•

We studied expectancy-related brain activity in pedophilic offenders and controls.

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Activation during anticipation elicits reactivity differences in salience network.

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Brain activation during expectancy was stronger compared to picture perception.

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Effects in dACC of patients and controls were found in 2 fMRI studies (1.5 and 7 T).

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DACC activation during expectancy revealed preference specificity in both groups.

The neural and genetic correlates of satisfying sexual activity in heterosexual pair-bonds

INTRODUCTION

In humans, satisfying sexual activity within a pair-bond plays a significant role in relationship quality and maintenance, beyond reproduction. However, the neural and genetic correlates for this basic species-supporting function, in response to a pair-bonded partner, are unknown.

METHODS

We examined the neural correlates of oxytocin- (Oxtr rs53576) and vasopressin- (Avpr1a rs3) receptor genotypes with sexual satisfaction and frequency, among a group of individuals in pair-bonds (M relationship length = 4.1 years). Participants were scanned twice (with functional MRI), about 1-year apart, while viewing face images of their spouse and a familiar, neutral acquaintance.

RESULTS

Sex satisfaction scores showed significant interactions with Oxtr and Avpr variants associated with social behaviors in a broad network of regions involved in reward and motivation (ventral tegmental area, substantia nigra [SN], and caudate), social bonding (ventral pallidum), emotion and memory (amygdala/hippocampus), hormone control (hypothalamus); and somatosensory and self-other processing (SII, frontal, and temporal lobe). Sexual frequency interactions also showed activations in the SN and paraventricular hypothalamus for Avpr, and the prefrontal cortex for Oxtr.

CONCLUSIONS

Satisfying sexual activity in pair-bonds is associated with activation of subcortical structures that support basic motivational and physiological processes; as well as cortical regions that mediate complex thinking, empathy, and self-other processes highlighting the multifaceted role of sex in pair-bonds. Oxtr and Avpr gene variants may further amplify both basic and complex neural processes for pair-bond conservation and well-being.

Meta-analytic Evidence for Neural Dysactivity Underlying Sexual Dysfunction

INTRODUCTION

About 30-40% of the population report sexual dysfunction. Although it is well known that the brain controls sexual behavior, little is known about the neural basis of sexual dysfunction.

AIM

To assess convergence of altered brain activity associated with sexual dysfunction across available functional imaging studies.

METHODS

We used activation likelihood estimation meta-analysis to quantify interstudy concordance across 14 functional imaging studies reporting 179 foci from 40 individual analyses involving 191 subjects with sexual dysfunction and 123 controls.

MAIN OUTCOME MEASURE

Activation likelihood estimation scores were used to assess convergence of findings.

RESULTS

Consistently decreased brain activity associated with sexual dysfunction was identified in the dorsal anterior cingulate cortex, ventral striatum, dorsal midbrain, anterior midcingulate cortex, and lateral orbitofrontal cortex.

CLINICAL IMPLICATION

These findings can serve as a basis for further studies on the pathophysiology of this highly common disorder with the view to development of more-specific treatment strategies.

STRENGTH & LIMITATIONS

Findings are based on an observer-independent meta-analysis that provides robust evidence for and anatomic localization of altered brain activity related to sexual dysfunction. Our analysis cannot distinguish between the putative sources of sexual dysfunction, but it provides a more ubiquitous and general pattern of related altered neural activity.

CONCLUSION

The identified regions have previously been shown to be critically involved in mediating sexual arousal and to be part of the sympathetic division of the autonomic nervous system. This suggests that the disturbance of brain activity associated with sexual dysfunction primarily affects sexual arousal already at early stages that are controlled by the sympathetic nervous system. Poeppl TB, Langguth B, Laird AR, et al. Meta-analytic Evidence for Neural Dysactivity Underlying Sexual Dysfunction. J Sex Med 2019;16:614-617.

Serotonergic, Dopaminergic, and Noradrenergic Modulation of Erotic Stimulus Processing in the Male Human Brain

Human sexual behavior is mediated by a complex interplay of cerebral and spinal centers, as well as hormonal, peripheral, and autonomic functions. Neuroimaging studies identified central neural signatures of human sexual responses comprising neural emotional, motivational, autonomic, and cognitive components. However, empirical evidence regarding the neuromodulation of these neural signatures of human sexual responses was scarce for decades. Pharmacological functional magnetic resonance imaging (fMRI) provides a valuable tool to examine the interaction between neuromodulator systems and functional network anatomy relevant for human sexual behavior. In addition, this approach enables the examination of potential neural mechanisms regarding treatment-related sexual dysfunction under psychopharmacological agents. In this article, we introduce common neurobiological concepts regarding cerebral sexual responses based on neuroimaging findings and we discuss challenges and findings regarding investigating the neuromodulation of neural sexual stimulus processing. In particular, we summarize findings from our research program investigating how neural correlates of sexual stimulus processing are modulated by serotonergic, dopaminergic, and noradrenergic antidepressant medication in healthy males.

Multimodal MRI suggests that male homosexuality may be linked to cerebral midline structures

The neurobiology of sexual preference is often discussed in terms of cerebral sex dimorphism. Yet, our knowledge about possible cerebral differences between homosexual men (HoM), heterosexual men (HeM) and heterosexual women (HeW) are extremely limited. In the present MRI study, we addressed this issue investigating measures of cerebral anatomy and function, which were previously reported to show sex difference. Specifically, we asked whether there were any signs of sex atypical cerebral dimorphism among HoM, if these were widely distributed (providing substrate for more general 'female' behavioral characteristics among HoM), or restricted to networks involved in self-referential sexual arousal. Cortical thickness (Cth), surface area (SA), subcortical structural volumes, and resting state functional connectivity were compared between 30 (HoM), 35 (HeM) and 38 (HeW). HoM displayed a significantly thicker anterior cingulate cortex (ACC), precuneus, and the left occipito-temporal cortex compared to both control groups. These differences seemed coordinated, since HoM also displayed stronger cortico-cortical covariations between these regions. Furthermore, functional connections within the default mode network, which mediates self- referential processing, and includes the ACC and precuneus were significantly weaker in HoM than HeM and HeW, whereas their functional connectivity between the thalamus and hypothalamus (important nodes for sexual behavior) was stronger. In addition to these singular features, HoM displayed 'female' characteristics, with a similar Cth in the left superior parietal and cuneus cortices as HeW, but different from HeM. These data suggest both singular and sex atypical features and motivate further investigations of cerebral midline structures in relation to male homosexuality.

Post-finasteride syndrome and post-SSRI sexual dysfunction: two sides of the same coin?

Sexual dysfunction is a clinical condition due to different causes including the iatrogenic origin. For instance, it is well known that sexual dysfunction may occur in patients treated with antidepressants like selective serotonin reuptake inhibitors (SSRI). A similar side effect has been also reported during treatment with finasteride, an inhibitor of the enzyme 5alpha-reductase, for androgenetic alopecia. Interestingly, sexual dysfunction persists in both cases after drug discontinuation. These conditions have been named post-SSRI sexual dysfunction (PSSD) and post-finasteride syndrome (PFS). In particular, feeling of a lack of connection between the brain and penis, loss of libido and sex drive, difficulty in achieving an erection and genital paresthesia have been reported by patients of both conditions. It is interesting to note that the incidence of these diseases is probably so far underestimated and their etiopathogenesis is not sufficiently explored. To this aim, the present review will report the state of art of these two different pathologies and discuss, on the basis of the role exerted by three different neuromodulators such as dopamine, serotonin and neuroactive steroids, whether the persistent sexual dysfunction observed could be determined by common mechanisms.

Mental Insanity Assessment of Pedophilia: The Importance of the Trans-Disciplinary Approach. Reflections on Two Cases

A 60 plus-year-old male was charged with pedophilia for forcing a child to touch him inappropriately near a primary school fence. In another case, a 70 plus-year-old male was charged with pedophilia for intimately touching a boy in a cinema. What led them to manifest this socially-inappropriate and legally-relevant behavior? Is there an explanation for the sexually-related behavioral changes emerging late in life of these two men? Indeed, a common point exists between the two men: both were found to suffer from highly-disabling neurological conditions, known to have a potential effect on social behavior. Specifically, a large right frontoparietal meningioma was found to have important influence on the first man's cognition and control inhibition, whereas frontotemporal dementia prevented the second man from understanding the moral disvalue of his sexually-inappropriate behavior and controlling his sexual impulses. In the current presentation, particular emphasis is placed on the logical reasoning supporting the conclusions that both the pedophiles should be considered not guilty by reason of insanity. Furthermore, experimental methods have been used to explore both cases, which rely on the existence of cognitive models for the phenomena under study, the integration of insights offered by different disciplines and the application of a variety of tools and approaches that follow the "convergence of evidence" principle, which could be safely used in court to support a mental insanity claim. Here, we describe how the use of the experimental method could become useful to reduce the uncertainty in mental insanity assessments. The use of a transdisciplinary, scientifically-grounded approach can help to change the way legal phenomena are interpreted. For instance, when assessing mental insanity, consultants should not only investigate the eventual existence of a diagnosis, but should assess the cognitive/affective abilities that are necessary to understand our own behavior and emotions as well as those of others. The criteria for responsibility should be symptoms-based and not diagnosis-based. Since pedophilia is among the most hideous behaviors condemned by society, a more comprehensive and transdisciplinary approach is recommended in court.

Molecular basis of androgen action on human sexual desire

Reproduction is a fundamental process for the species maintenance and the propagation of genetic information. The energy expenditure for mating is overtaken by motivational stimuli, such as orgasm, finely regulated by steroid hormones, gonadotropins, neurotransmitters and molecules acting in the brain and peripheral organs. These functions are often investigated using animal models and translated to humans, where the androgens action is mediated by nuclear and membrane receptors converging in the regulation of both long-term genomic and rapid non-genomic signals. In both sexes, testosterone is a central player of this game and is involved in the regulation of sexual desire and arousal, and, finally, in reproduction through cognitive and peripheral physiological mechanisms which may decline with aging and circadian disruption. Finally, genetic variations impact on reproductive behaviours, resulting in sex-specific effect and different reproductive strategies. In this review, androgen actions on sexual desire are evaluated, focusing on the molecular levels of interaction.

Positron emission tomography assessment of cerebral glucose metabolic rates in autism spectrum disorder and schizophrenia

Several models have been proposed to account for observed overlaps in clinical features and genetic predisposition between schizophrenia and autism spectrum disorder. This study assessed similarities and differences in topological patterns and vectors of glucose metabolism in both disorders in reference to these models. Co-registered 18fluorodeoxyglucose PET and MRI scans were obtained in 41 schizophrenia, 25 ASD, and 55 healthy control subjects. AFNI was used to map cortical and subcortical regions of interest. Metabolic rates were compared between three diagnostic groups using univariate and multivariate repeated-measures ANOVA. Compared to controls, metabolic rates in schizophrenia subjects were decreased in the frontal lobe, anterior cingulate, superior temporal gyrus, amygdala and medial thalamic nuclei; rates were increased in the occipital cortex, hippocampus, basal ganglia and lateral thalamic nuclei. In ASD subjects metabolic rates were decreased in the parietal lobe, frontal premotor and eye-fields areas, and amygdala; rates were increased in the posterior cingulate, occipital cortex, hippocampus and basal ganglia. In relation to controls, subjects with ASD and schizophrenia showed opposite changes in metabolic rates in the primary motor and somatosensory cortex, anterior cingulate and hypothalamus; similar changes were found in prefrontal and occipital cortices, inferior parietal lobule, amygdala, hippocampus, and basal ganglia. Schizophrenia and ASD appear to be associated with a similar pattern of metabolic abnormalities in the social brain. Divergent maladaptive trade-offs, as postulated by the diametrical hypothesis of their evolutionary relationship, may involve a more circumscribed set of anterior cingulate, motor and somatosensory regions and the specific cognitive functions they subserve.

How Hot Are They? Neural Correlates of Genital Arousal: An Infrared Thermographic and Functional Magnetic Resonance Imaging Study of Sexual Arousal in Men and Women

BACKGROUND

The few studies that have examined the neural correlates of genital arousal have focused on men and are methodologically hard to compare.

AIM

To investigate the neural correlates of peripheral physiologic sexual arousal using identical methodology for men and women.

METHODS

2 groups (20 men, 20 women) viewed movie clips (erotic, humor) while genital temperature was continuously measured using infrared thermal imaging. Participants also continuously evaluated changes in their subjective arousal and answered discrete questions about liking the movies and wanting sexual stimulation. Brain activity, indicated by blood oxygen level-dependent (BOLD) response, was measured using functional magnetic resonance imaging.

OUTCOMES

BOLD responses, genital temperature, and subjective sexual arousal.

RESULTS

BOLD activity in a number of brain regions was correlated with changes in genital temperature in men and women; however, activation in women appeared to be more extensive than in men, including the anterior and posterior cingulate cortex, right cerebellum, insula, frontal operculum, and paracingulate gyrus. Examination of the strength of the correlation between BOLD response and genital temperature showed that women had a stronger brain-genital relation compared with men in a number of regions. There were no brain regions in men with stronger brain-genital correlations than in women.

CLINICAL TRANSLATION

Our findings shed light on the neurophysiologic processes involved in genital arousal for men and women. Further research examining the specific brain regions that mediate our findings is necessary to pave the way for clinical application.

STRENGTHS AND LIMITATIONS

A strength of the study is the use of thermography, which allows for a direct comparison of the neural correlates of genital arousal in men and women. This study has the common limitations of most laboratory-based sexual arousal research, including sampling bias, lack of ecologic validity, and equipment limitations, and those common to neuroimaging research, including BOLD signal interpretation and neuroimaging analysis issues.

CONCLUSIONS

Our findings provide direct sex comparisons of the neural correlates of genital arousal in men and women and suggest that brain-genital correlations could be stronger in women. Parada M, Gérard M, Larcher K, et al. How Hot Are They? Neural Correlates of Genital Arousal: An Infrared Thermographic and Functional Magnetic Resonance Imaging Study of Sexual Arousal in Men and Women. J Sex Med 2018;15:217-229.

Resting State Functional Connectivity of the Lateral and Medial Hypothalamus in Cocaine Dependence: An Exploratory Study

The role of dopamine in cocaine misuse has been extensively documented for the mesocorticolimbic circuit. Preclinical work from earlier lesion studies to recent multidisciplinary investigations has suggested that the hypothalamus is critically involved in motivated behavior, with the lateral and medial hypothalamus each involved in waking/feeding and resting/satiety. However, little is known of hypothalamus function and dysfunction in cocaine misuse. Here, we examined resting state functional connectivity of the lateral and medial hypothalamus in 70 individuals with cocaine dependence (CD) and 70 age as well as gender matched healthy controls (HC). Image pre-processing and analyses followed published work. Compared to HC, CD showed increased lateral hypothalamic connectivity with dorsolateral prefrontal cortex and decreased functional connectivity with the ventral precuneus. CD showed increased medial hypothalamic connectivity with the inferior parietal lobule and decreased connectivity with the ventromedial prefrontal cortex, temporal gyrus, fusiform gyrus, and ventral striatum. Further, at trend level significance, the connectivity strength between lateral hypothalamus and dorsolateral prefrontal cortex was positively correlated with total amount of cocaine use in the past month (p = 0.004, r = 0.35) and the connectivity strength between medial hypothalamus and ventral striatum was negatively correlated with cocaine craving as assessed by the Tiffany Cocaine Craving Questionnaire (p = 0.008, r = -0.33). Together, the findings demonstrated altered resting state functional connectivity of the hypothalamus and may provide new insight on circuit level deficits in cocaine dependence.

Brain Imaging of Human Sexual Response: Recent Developments and Future Directions

PURPOSE OF REVIEW

The purpose of this study is to provide a comprehensive summary of the latest developments in the experimental brain study of human sexuality, focusing on brain connectivity during the sexual response.

RECENT FINDINGS

Stable patterns of brain activation have been established for different phases of the sexual response, especially with regard to the wanting phase, and changes in these patterns can be linked to sexual response variations, including sexual dysfunctions. From this solid basis, connectivity studies of the human sexual response have begun to add a deeper understanding of the brain network function and structure involved.

SUMMARY

The study of "sexual" brain connectivity is still very young. Yet, by approaching the brain as a connected organ, the essence of brain function is captured much more accurately, increasing the likelihood of finding useful biomarkers and targets for intervention in sexual dysfunction.