Reward sensitivity is associated with brain activity during erotic stimulus processing

The Complex Role Played by the Default Mode Network during Sexual Stimulation: A Cluster-Based fMRI Meta-Analysis

The default mode network (DMN) is a complex network that plays a significant and active role during naturalistic stimulation. Previous studies that have used naturalistic stimuli, such as real-life stories or silent or sonorous films, have found that the information processing involved a complex hierarchical set of brain regions, including the DMN nodes. The DMN is not involved in low-level features and is only associated with high-level content-related incoming information. The human sexual experience involves a complex set of processes related to both external context and inner processes. Since the DMN plays an active role in the integration of naturalistic stimuli and aesthetic perception with beliefs, thoughts, and episodic autobiographical memories, we aimed at quantifying the involvement of the nodes of the DMN during visual sexual stimulation. After a systematic search in the principal electronic databases, we selected 83 fMRI studies, and an ALE meta-analysis was calculated. We performed conjunction analyses to assess differences in the DMN related to stimulus modalities, sex differences, and sexual orientation. The results show that sexual stimulation alters the topography of the DMN and highlights the DMN's active role in the integration of sexual stimuli with sexual schemas and beliefs.

Social Signal Processing in Affective Virtual Reality: Human-Shaped Agents Increase Electrodermal Activity in an Elicited Negative Environment

Prior research on affect elicitation indicates that stimuli with social content (pictures or videos) are more arousing than nonsocial stimuli. In particular, they elicit stronger physiological arousal as measured by electrodermal activity (EDA; i.e., social EDA effect). However, it is unclear how this effect applies to virtual reality (VR), which enables an enhanced sense of presence (SoP) and ecological validity. The study here approached this question from a social-emotional VR framework. A sample of N = 72 participants (55 percent women) experienced a set of six virtual environments (VEs) in the form of emotional parks specifically designed to elicit positive, negative, or neutral affectivity. Half of these VEs included human-shaped agents (social context) and the other half omitted these agents (nonsocial context). The results supported the social EDA effect, which in addition was amplified by the reported SoP. Importantly, the VE featuring a social negative content qualified this observed social EDA effect. The finding is discussed in the light of a negativity bias reported in affect literature, through which negative stimuli typically mobilize attention and bodily activation as a mechanism linked to stress responses. The study's implications extend to the use of VR in both research and practical applications, emphasizing the role of social content in influencing affective and physiological responses.

Two subtypes of compulsive sexual behavior disorder

Models explaining addictive behaviors such as the Interaction of Person-Affect-Cognition-Execution (I-PACE) model emphasize the importance of reinforcement mechanisms for developing and maintaining these behaviors, including compulsive sexual behavior disorder (CSBD) as well as personal characteristics as vulnerability factors. This study aimed to determine whether there are CSBD subtypes distinguished by reinforcement sensitivity. We hypothesize that one subtype is sensitive to positive reinforcement (C+subtype) and one is sensitive to negative reinforcement (Ȼ-subtype). We calculated a cluster analysis with data from 62 patients with CSBD and tested differences between the identified clusters by t-test. The sample consisted only of men. Cluster variables were: the sensitivity to the Behavioral Inhibition and Approach System (BIS/BAS), the severity of depressive symptoms (BDI-II), the severity of Trait Anxiety (STAI-T), Sexual Sensation Seeking (SSSS), Thrill- and Adventure-Seeking (SSS-V subscale), Disinhibition (SSS-V subscale), Experience Seeking (SSS-V subscale), and Boredom Susceptibility (SSS-V subscale). Between-cluster differences were analyzed for Trait Sexual Motivation (TSMQ) and Sexual Compulsivity (SCS). The results showed a two-cluster solution with cluster 1 representing patients sensitive to negative reinforcement (Ȼ-subtype) and cluster 2 representing patients sensitive to positive reinforcement (C+subtype). No significant difference in symptom severity of Sexual Compulsivity between clusters was found. Cluster 2 showed higher Importance of Sex and a higher motivation to seek sexual encounters than cluster 2. We found a two-cluster solution regarding reinforcement sensitivity in patients with CSBD. This may have clinical implications regarding individual therapy by focusing on the underlying maintenance mechanisms.

No significant effect of frequent online sexual behaviour on Pavlovian-to-instrumental transfer (PIT): Implications for compulsive sexual behaviour disorder

Reward based learning is broadly acknowledged to underpin the development and maintenance of addictive behaviour although the mechanism in sexual compulsivity is less understood. Using a Pavlovian-to-Instrumental Transfer (PIT) task we tested whether the motivational aspect of conditioned Pavlovian conditioned stimulus invigorated instrumental responding in relation to specific compatible monetary rewards. Performance on the task was analysed between two groups of males based on Low (N = 38) and High (N = 41) self-report online sexual behaviour (OSB). Psychometric tests including sexual compulsivity scale and behavioural activation/behavioural inhibition (BIS/BAS) were also administered to determine the relationship between OSB and general reward sensitivity. We show clear evidence of acquisition in the Pavlovian and instrumental conditioning phases. Specific transfer effect was greater in the High-OSB group although the difference compared to the Low-OSB group was non-significant. OSB negatively correlated with both BIS and BAS indicative of introversion and low reward sensitivity. OSB positively correlated with sexual compulsivity although it is unclear whether individuals in the High-OSB group considered their behaviour either excessive or problematic. These findings contribute to the ongoing debate regarding the nature of problematic OSB. Fundamental differences in motivational characteristics and mechanism contributing to compulsive behaviour in relation to high-OSB might indicate incompatibility with behavioural addiction models. PIT was not enhanced in high-OSB by appetitive conditioning, although problematic OSB could stem from failure to inhibit actions. Further research should investigate whether aversive conditioning differentially affects responding in high-OSB individuals, potentially explaining perseverant behaviour despite negative consequences.

Functional Connectivity of Nucleus Accumbens Is Associated with Lifelong Premature Ejaculation in Male Adults : A Resting-state fMRI Study

PURPOSE

Ejaculation represents a crucial component of sexual behavior in men, which is involved in reward functions of certain brain areas including the nucleus accumbens (NAcc). Lifelong premature ejaculation (PE) is one of the most prevalent sexual dysfunctions in men. It is suggested to be related to abnormal brain function. This study aimed to explore changes of the functional connectivity patterns of NAcc and possible correlations of the neuroimaging abnormalities with clinical features in lifelong PE patients.

METHODS

The sample consisted with 42 lifelong PE patients and 30 healthy controls. All participants underwent functional magnetic resonance imaging scans and clinical symptoms. The functional connectivity (FC) approach was applied to investigate differences of NAcc-seed intrinsic connectivity between two groups and correlation analysis was used to access possible relationships between the imaging findings and clinical features, such as premature ejaculation diagnostic tool (PEDT) or intravaginal ejaculatory latency time (IELT).

RESULTS

Results showed that lifelong PE patients had decreased FC between the NAcc and thalamus, superior temporal pole, superior temporal cortex (STC), inferior frontal gyrus (IFG), orbitofrontal cortex, caudate and putamen. A significantly negative correlation between the PEDT score and NAcc-STC connectivity (r = -0.46) was found in lifelong PE patients, while IELT score positively correlated with the NAcc-IFG connectivity (r = 0.48) and NAcc-thalamus connectivity (r = 0.46).

CONCLUSION

The findings may facilitate a more sophisticated understanding of neural mechanisms of lifelong PE, particularly associated with the NAcc-related intrinsic connectivity during the resting state.

Interdependent Neural Correlates of Reward and Punishment Sensitivity During Rewarded Action and Inhibition of Action

Imaging studies have distinguished the brain correlates of approach and avoidance behaviors and suggested the influence of individual differences in trait sensitivity to reward (SR) and punishment (SP) on these neural processes. Theoretical work of reinforcement sensitivity postulates that SR and SP may interdependently regulate behavior. Here, we examined the distinct and interrelated neural substrates underlying rewarded action versus inhibition of action in relation to SR and SP as evaluated by the Sensitivity to Punishment and Sensitivity to Reward Questionnaire. Forty-nine healthy adults performed a reward go/no-go task with approximately 2/3 go and 1/3 no-go trials. Correct go and no-go responses were rewarded and incorrect responses were penalized. The results showed that SR and SP modulated rewarded go and no-go, respectively, both by recruiting the rostral anterior cingulate cortex and left middle frontal gyrus (rACC/left MFG). Importantly, SR and SP influenced these regional activations in opposite directions, thus exhibiting an antagonistic relationship as suggested by the reinforcement sensitivity theory. Furthermore, mediation analysis revealed that heightened SR contributed to higher rewarded go success rate via enhanced rACC/left MFG activity. The findings demonstrate interrelated neural correlates of SR and SP to support the diametric processes of behavioral approach and avoidance.

Trauma-related dysfunction in the fronto-striatal reward circuit

INTRODUCTION

Reduced reactivity to pleasurable stimulation is a defining symptom of post-traumatic stress disorder (PTSD), but trauma exposure also increases the severity of many anxiety and mood disorders, including depression, social anxiety, and panic disorder, suggesting that reward system dysfunction might be pervasive in the internalizing disorders. The ventromedial prefrontal cortex (vmPFC) and ventral striatum are core components of the reward circuit and the current study assesses functional activity and connectivity in this circuit during emotional picture viewing in anxiety and mood disorder patients.

METHOD

Functional brain activity (fMRI) and functional connectivity in the fronto-striatal circuit were measured in a large sample of patients diagnosed with anxiety and mood disorders (n=155) during affective scene viewing as it varied with trauma exposure and temperament.

RESULTS

In women, but not men, blunted fronto-striatal connectivity was associated with increased posttraumatic anhedonic symptoms, whereas the amplitude of functional activity was not related to trauma exposure. In both men and women, reduced fronto-striatal connectivity was associated with decreases in temperamental positive affect. When predicting fronto-striatal connectivity, temperament and posttraumatic symptomology accounted for independent proportions of variance.

LIMITATIONS

In this civilian sample of anxiety disorder patients, men reported very little trauma-related symptomology.

CONCLUSIONS

Because dysfunctional reward processing due to trauma and temperament is pervasive across the internalizing disorder spectrum, assessing the integrity of the fronto-striatal reward circuit could provide important information in diagnostic and treatment protocols.

Basal ganglia lateralization in different types of reward

Reward processing is a fundamental human activity. The basal ganglia are recognized for their role in reward processes; however, specific roles of the different nuclei (e.g., nucleus accumbens, caudate, putamen and globus pallidus) remain unclear. Using quantitative meta-analyses we assessed whole-brain and basal ganglia specific contributions to money, erotic, and food reward processing. We analyzed data from 190 fMRI studies which reported stereotaxic coordinates of whole-brain, within-group results from healthy adult participants. Results showed concordance in overlapping and distinct cortical and sub-cortical brain regions as a function of reward type. Common to all reward types was concordance in basal ganglia nuclei, with distinct differences in hemispheric dominance and spatial extent in response to the different reward types. Food reward processing favored the right hemisphere; erotic rewards favored the right lateral globus pallidus and left caudate body. Money rewards engaged the basal ganglia bilaterally including its most anterior part, nucleus accumbens. We conclude by proposing a model of common reward processing in the basal ganglia and separate models for money, erotic, and food rewards.

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.

The Role of Social Reward and Corticostriatal Connectivity in Substance Use

This report describes an ongoing R03 grant that explores the links between trait reward sensitivity, substance use, and neural responses to social and nonsocial reward. Although previous research has shown that trait reward sensitivity and neural responses to reward are linked to substance use, whether this relationship is impacted by how people process social stimuli remains unclear. We are investigating these questions via a neuroimaging study with college-aged participants, using individual difference measures that examine the relation between substance use, social context, and trait reward sensitivity with tasks that measure reward anticipation, strategic behavior, social reward consumption, and the influence of social context on reward processing. We predict that substance use will be tied to distinct patterns of striatal dysfunction. Specifically, reward hyposensitive individuals will exhibit blunted striatal responses to social and non-social reward and enhanced connectivity with the orbitofrontal cortex; in contrast, reward hypersensitive individuals will exhibit enhanced striatal responses to social and non-social reward and blunted connectivity with the orbitofrontal cortex. We also will examine the relation between self-reported reward sensitivity, substance use, and striatal responses to social reward and social context. We predict that individuals reporting the highest levels of substance use will show exaggerated striatal responses to social reward and social context, independent of self-reported reward sensitivity. Examining corticostriatal responses to reward processing will help characterize the relation between reward sensitivity, social context and substance use while providing a foundation for understanding risk factors and isolating neurocognitive mechanisms that may be targeted to increase the efficacy of interventions.

Reward network connectivity "at rest" is associated with reward sensitivity in healthy adults: A resting-state fMRI study

The behavioral approach system (BAS), based on reinforcement sensitivity theory (RST), is a neurobehavioral system responsible for detecting and promoting motivated behaviors towards appetitive stimuli. Anatomically, the frontostriatal system has been proposed as the core of the BAS, mainly the ventral tegmental area and the ventral striatum and their dopaminergic connections with medial prefrontal structures. The RST also proposes the personality trait of reward sensitivity as a measurable construct of stable individual differences in BAS activity. However, the relationship between this trait and brain connectivity "at rest" has been poorly studied, mainly because previous investigations have focused on studying brain activity under reward-related contingency paradigms. Here, we analyzed the influence of reward sensitivity on the resting-state functional connectivity (rs-FC) between BAS-related areas by correlating the BOLD time series with the scores on the Sensitivity to Reward (SR) scale in a sample of 89 healthy young adults. Rs-FC between regions of interest were all significant. Results also revealed a positive association between SR scores and the rs-FC between the VTA and the ventromedial prefrontal cortex, and between the latter structure and the anterior cingulate cortex. These results suggest that reward sensitivity could be associated with different resting-state activity in the mesocortical pathway.

Different Neural Correlates of Sexually Preferred and Sexually Nonpreferred Stimuli

BACKGROUND

The differences and relationships between stimulus-related brain activation for sexually preferred stimuli and sexually nonpreferred stimuli are still unclear.

AIM

This study aimed to identify brain regions that were mostly associated with sexual stimuli.

METHODS

We used the activation likelihood estimation, meta-analytic connectivity modelling, and behavioral domain metadata in the BrainMap database to perform this analysis.

OUTCOMES

We found convergent activation foci and created a model for the extended brain network involved in responses to sexual stimuli and also assessed the functional properties of these regions.

RESULTS

A total of 34 experiments from 15 studies including 368 subjects and 343 foci were analyzed. The results showed that sexual stimuli are related to the extensive activation of the occipital-temporal-limbic system and less extensive activation of the basal ganglia. Sexually preferred stimuli activated mainly the anterior cingulate cortex and right fusiform gyrus, while sexually nonpreferred stimuli activated the limbic system, occipital gyrus, and thalamus.

CLINICAL IMPLICATIONS

To have a further understanding of the central mechanisms of human sexuality.

STRENGTHS & LIMITATIONS

Patient characteristics and analysis techniques in the included studies were heterogeneous.

CONCLUSIONS

These findings suggest that the anterior cingulate cortex is an important cognitive control area for both sexually preferred and nonpreferred stimuli. Meta-analytic connectivity modelling analysis revealed a network of the core brain areas involved in response to sexual stimuli, and behavioral domain analysis indicated that these areas have both common and discrete functional properties. Long X, Tian F, Zhou Y, et al. Different Neural Correlates of Sexually Preferred and Sexually Nonpreferred Stimuli. J Sex Med 2020;17:1254-1267.

Altered Functional Connectivity of Hypothalamus in Lifelong Premature Ejaculation Patients

BACKGROUND

As one of the most prevalent sexual dysfunctions in men, lifelong premature ejaculation (PE) often leads to patient distress. The hypothalamus is implicated in the ejaculatory control of healthy males. However, we do not know whether the hypothalamus-related intrinsic connectivity is altered in lifelong PE patients.

PURPOSE

To investigate abnormal intrinsic connectivity of the hypothalamus in lifelong PE patients compared with healthy controls (HCs).

STUDY TYPE

Prospective pilot study using cross-sectional data of patients and HCs.

SUBJECTS

Forty-seven lifelong PE patients and 30 HCs were included in this study.

FIELD STRENGTH/SEQUENCE

3.0T MRI scanner for T₁ -weighted imaging using spoiled gradient recalled echo sequence and functional imaging using a single-shot gradient recalled echo sequence.

ASSESSMENT

Preprocessing of MRI data and hypothalamus-seeded functional connectivity (FC) computation were performed using DPABI4.1.

STATISTICAL TESTS

The two-sample t-test within SPM12 was adopted to examine possible alterations of intrinsic connectivity of hypothalamus in lifelong PE patients compared with HCs including anxiety and depression scores as covariates (false discovery rate-corrected, P < 0.05). The correlation analysis was then used to assess possible associations between the imaging findings and clinical features in the patient group (Bonferroni-corrected, P < 0.05).

RESULTS

Compared with HCs, lifelong PE patients had decreased hypothalamus-seeded FC in the left orbitofrontal cortex, bilateral insula, superior temporal cortex, superior temporal pole, middle temporal cortex, left fusiform, right parahippocampal gyrus, and right cerebellum. The intravaginal ejaculatory latency time positively correlated with the mean z-score from the hypothalamus-insula (r = 0.45) and hypothalamus-cerebellum (r = 0.48) intrinsic connectivity, separately.

DATA CONCLUSION

We have shown that hypothalamus-seeded FC alterations and the correlations between the aforementioned abnormal FC alterations and intravaginal ejaculatory latency time. The current findings may promote the understanding of the hypothalamus-related neural mechanisms involved in the abnormal ejaculatory information processing in lifelong PE patients.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 3 J. Magn. Reson. Imaging 2020;52:778-784.

Short- and long-range synergism disorders in lifelong premature ejaculation evaluated using the functional connectivity density and network property

This study was aimed to investigate brain function connectivity in premature ejaculation (PE) patients using the functional connectivity density (FCD) and network property of resting-state functional magnetic resonance imaging. Twenty PE patients (mean age: 27.95 ± 4.52 years) and 15 normal controls (mean age: 27.87 ± 3.78 years) with no self-reported history of neurologic or psychiatric disease were enrolled in this study. International Index of Erectile Function-5 and Chinese Index of Sexual Function for Premature Ejaculation-5 questionnaires and self-reported intravaginal ejaculatory latency time (IELT) were obtained from each participant for symptom assessment. Two-sample t-tests (intergroup comparison) were applied in the short-range FCD (SFCD) analysis, long-range FCD (LFCD) analysis, region of interest–based analysis, and network topological organization analysis. Pearson correlation analysis was performed to correlate IELT with FCD or the network property. The patients with PE showed significantly decreased SFCD in the bilateral middle temporal gyrus, left orbitofrontal cortex, nucleus accumbens, fusiform, caudate, and thalamus (p < 0.05, AlphaSim-corrected). Notably, all these aforementioned brain areas are located in the dopamine pathway. In contrast, increased LFCD was observed in the left insula, Heschl's gyrus, putamen, bilateral precuneus, supplementary motor area, middle cingulate cortex, and anterior cingulate cortex in PE patients (p < 0.05, AlphaSim-corrected). In addition, the network topological analysis found reinforced network connectivity between several nodes. The degree of hub nodes increased in the patients with PE. IELT was positively correlated with SFCD and negatively correlated with LFCD or the degree of hub nodes (p < 0.05, Pearson correlation). In summary, our results are important for understanding the brain network in PE patients. The present findings indicate that PE patients have a significant synergism disorder across the region of dopamine pathway, which implied neuronal pathological changes might be related with the change of dopamine. The FCD and network property can serve as new disease severity biomarkers and therapeutic targets in PE.

•

PE patients have different patterns of FCD compared with normal controls.

•

The functional brain network efficiency has changed in PE patients.

•

The FCD and network property can serve as disease severity biomarkers.

BAS-drive trait modulates dorsomedial striatum activity during reward response-outcome associations

According to the Reinforcement Sensitivity Theory, behavioral studies have found that individuals with stronger reward sensitivity easily detect cues of reward and establish faster associations between instrumental responses and reward. Neuroimaging studies have shown that processing anticipatory cues of reward is accompanied by stronger ventral striatum activity in individuals with stronger reward sensitivity. Even though establishing response-outcome contingencies has been consistently associated with dorsal striatum, individual differences in this process are poorly understood. Here, we aimed to study the relation between reward sensitivity and brain activity while processing response-reward contingencies. Forty-five participants completed the BIS/BAS questionnaire and performed a gambling task paradigm in which they received monetary rewards or punishments. Overall, our task replicated previous results that have related processing high reward outcomes with activation of striatum and medial frontal areas, whereas processing high punishment outcomes was associated with stronger activity in insula and middle cingulate. As expected, the individual differences in the activity of dorsomedial striatum correlated positively with BAS-Drive. Our results agree with previous studies that have related the dorsomedial striatum with instrumental performance, and suggest that the individual differences in this area may form part of the neural substrate responsible for modulating instrumental conditioning by reward sensitivity.

Meta-analysis of the relationship between impulsivity and substance-related cognitive biases

BACKGROUND

Evidence indicates that substance-related cognitive biases (attentional, memory, and approach bias) contribute to the maintenance and development of substance misuse. Impulsivity has been suggested to influence how cognitive biases contribute to substance misuse, possibly by biasing incentive salience attribution processes. However, the strength and moderators of the relationship between impulsivity and substance-related cognitive biases has yet to be empirically examined.

METHODS

A meta-analysis using random-effects models was completed assessing 19 studies that reported a quantitative relationship between an impulsivity measure and a substance-related cognitive bias. Two-component conceptualisation of impulsivity, impulsivity measurement type, gender, and age were assessed as moderators.

RESULTS

A small, significant positive relationship (r=0.10) was observed between impulsivity and substance-related attentional, memory, and approach biases. No moderators examined had a significant influence on this relationship.

CONCLUSIONS

Results are consistent with incentive sensitisation theories of addiction and suggests a weak synergistic relationship between impulsivity and substance-related cognitive biases. This relationship holds across different measures and components of impulsivity. Results provide some support for the viability of impulsivity and cognitive bias interaction models which may warrant further investigation of these factors in relation to predicting addiction treatment outcomes.

Reduced activity in functional networks during reward processing is modulated by abstinence in cocaine addicts

Cocaine addiction is characterized by alterations in motivational and cognitive processes. Recent studies have shown that some alterations present in cocaine users may be related to the activity of large functional networks. The aim of this study was to investigate how these functional networks are modulated by non-drug rewarding stimuli in cocaine-dependent individuals. Twenty abstinent cocaine-dependent and 21 healthy matched male controls viewed erotic and neutral pictures while undergoing a functional magnetic resonance imaging scan. Group independent component analysis was then performed in order to investigate how functional networks were modulated by reward in cocaine addicts. The results showed that cocaine addicts, compared with healthy controls, displayed diminished modulation of the left frontoparietal network in response to erotic pictures, specifically when they were unpredicted. Additionally, a positive correlation between the length of cocaine abstinence and the modulation of the left frontoparietal network by unpredicted erotic images was found. In agreement with current addiction models, our results suggest that cocaine addiction contributes to reduce sensitivity to rewarding stimuli and that abstinence may mitigate this effect.

Kisspeptin modulates sexual and emotional brain processing in humans

BACKGROUND. Sex, emotion, and reproduction are fundamental and tightly entwined aspects of human behavior. At a population level in humans, both the desire for sexual stimulation and the desire to bond with a partner are important precursors to reproduction. However, the relationships between these processes are incompletely understood. The limbic brain system has key roles in sexual and emotional behaviors, and is a likely candidate system for the integration of behavior with the hormonal reproductive axis. We investigated the effects of kisspeptin, a recently identified key reproductive hormone, on limbic brain activity and behavior.

METHODS. Using a combination of functional neuroimaging and hormonal and psychometric analyses, we compared the effects of kisspeptin versus vehicle administration in 29 healthy heterosexual young men.

RESULTS. We demonstrated that kisspeptin administration enhanced limbic brain activity specifically in response to sexual and couple-bonding stimuli. Furthermore, kisspeptin’s enhancement of limbic brain structures correlated with psychometric measures of reward, drive, mood, and sexual aversion, providing functional significance. In addition, kisspeptin administration attenuated negative mood.

CONCLUSIONS. Collectively, our data provide evidence of an undescribed role for kisspeptin in integrating sexual and emotional brain processing with reproduction in humans. These results have important implications for our understanding of reproductive biology and are highly relevant to the current pharmacological development of kisspeptin as a potential therapeutic agent for patients with common disorders of reproductive function.

FUNDING. National Institute for Health Research (NIHR), Wellcome Trust (Ref 080268), and the Medical Research Council (MRC).

Visual Sexual Stimuli-Cue or Reward? A Perspective for Interpreting Brain Imaging Findings on Human Sexual Behaviors

There is an increasing number of neuroimaging studies using visual sexual stimuli (VSS), especially within the emerging field of research on compulsive sexual behaviors (CSB). A central question in this field is whether behaviors such as excessive pornography consumption share common brain mechanisms with widely studied substance and behavioral addictions. Depending on how VSS are conceptualized, different predictions can be formulated within the frameworks of Reinforcement Learning or Incentive Salience Theory, where a crucial distinction is made between conditioned and unconditioned stimuli (related to reward anticipation vs. reward consumption, respectively). Surveying 40 recent human neuroimaging studies we show existing ambiguity about the conceptualization of VSS. Therefore, we feel that it is important to address the question of whether VSS should be considered as conditioned stimuli (cue) or unconditioned stimuli (reward). Here we present our own perspective, which is that in most laboratory settings VSS play a role of reward, as evidenced by: (1) experience of pleasure while watching VSS, possibly accompanied by genital reaction; (2) reward-related brain activity correlated with these pleasurable feelings in response to VSS; (3) a willingness to exert effort to view VSS similarly as for other rewarding stimuli such as money; and (4) conditioning for cues predictive of VSS. We hope that this perspective article will initiate a scientific discussion on this important and overlooked topic and increase attention for appropriate interpretations of results of human neuroimaging studies using VSS.

A neuroscience perspective on sexual risk behavior in adolescence and emerging adulthood

Late adolescence and emerging adulthood (specifically ages 15-24) represent a period of heightened sexual risk taking resulting in the greatest annual rates of sexually transmitted infections and unplanned pregnancies in the US population. Ongoing efforts to prevent such negative consequences are likely to benefit from a deepening of our understanding of biological mechanisms through which sexual risk taking emerges and biases decision making during this critical window. Here we present a neuroscience framework from which a mechanistic examination of sexual risk taking can be advanced. Specifically, we adapt the neurodevelopmental triadic model, which outlines how motivated behavior is governed by three systems: approach, avoidance, and regulation, to sexual decision making and subsequent risk behavior. We further propose a testable hypothesis of the triadic model, wherein relatively decreased threat-related amygdala reactivity and increased reward-related ventral striatum reactivity leads to sexual risk taking, which is particularly exaggerated during adolescence and young adulthood when there is an overexpression of dopaminergic neurons coupled with immature top-down prefrontal cortex regulation. We conclude by discussing how future research based on our adapted triadic model can inform ongoing efforts to improve intervention and prevention efforts.

Behavioural activation system sensitivity is associated with cerebral μ-opioid receptor availability

The reinforcement-sensitivity theory proposes that behavioural activation and inhibition systems (BAS and BIS, respectively) guide approach and avoidance behaviour in potentially rewarding and punishing situations. Their baseline activity presumably explains individual differences in behavioural dispositions when a person encounters signals of reward and harm. Yet, neurochemical bases of BAS and BIS have remained poorly understood. Here we used in vivo positron emission tomography with a µ-opioid receptor (MOR) specific ligand [(11)C]carfentanil to test whether individual differences in MOR availability would be associated with BAS or BIS. We scanned 49 healthy subjects and measured their BAS and BIS sensitivities using the BIS/BAS scales. BAS but not BIS sensitivity was positively associated with MOR availability in frontal cortex, amygdala, ventral striatum, brainstem, cingulate cortex and insula. Strongest associations were observed for the BAS subscale 'Fun Seeking'. Our results suggest that endogenous opioid system underlies BAS, and that differences in MOR availability could explain inter-individual differences in reward seeking behaviour.

Erotic subset for the Nencki Affective Picture System (NAPS ERO): cross-sexual comparison study

Research on the processing of sexual stimuli has proved that such material has high priority in human cognition. Yet, although sex differences in response to sexual stimuli were extensively discussed in the literature, sexual orientation was given relatively little consideration, and material suitable for relevant research is difficult to come by. With this in mind, we present a collection of 200 erotic images, accompanied by their self-report ratings of emotional valence and arousal by homo- and heterosexual males and females (n = 80, divided into four equal-sized subsamples). The collection complements the Nencki Affective Picture System (NAPS) and is intended to be used as stimulus material in experimental research. The erotic images are divided into five categories, depending on their content: opposite-sex couple (50), male couple (50), female couple (50), male (25) and female (25). Additional 100 control images from the NAPS depicting people in a non-erotic context were also used in the study. We showed that recipient sex and sexual orientation strongly influenced the evaluation of erotic content. Thus, comparisons of valence and arousal ratings in different subject groups will help researchers select stimuli set for the purpose of various experimental designs. To facilitate the use of the dataset, we provide an on-line tool, which allows the user to browse the images interactively and select proper stimuli on the basis of several parameters. The NAPS ERO image collection together with the data are available to the scientific community for non-commercial use at http://naps.nencki.gov.pl.

Exercising self-control increases relative left frontal cortical activation

Self-control refers to the capacity to override or alter a predominant response tendency. The current experiment tested the hypothesis that exercising self-control temporarily increases approach motivation, as revealed by patterns of electrical activity in the prefrontal cortex. Participants completed a writing task that did vs did not require them to exercise self-control. Then they viewed pictures known to evoke positive, negative or neutral affect. We assessed electroencephalographic (EEG) activity while participants viewed the pictures, and participants reported their trait levels of behavioral inhibition system (BIS) and behavioral activation system (BAS) sensitivity at the end of the study. We found that exercising (vs not exercising) self-control increased relative left frontal cortical activity during picture viewing, particularly among individuals with relatively higher BAS than BIS, and particularly during positive picture viewing. A similar but weaker pattern emerged during negative picture viewing. The results suggest that exercising self-control temporarily increases approach motivation, which may help to explain the aftereffects of self-control (i.e. ego depletion).

Longitudinal changes in adolescent risk-taking: a comprehensive study of neural responses to rewards, pubertal development, and risk-taking behavior

Prior studies have highlighted adolescence as a period of increased risk-taking, which is postulated to result from an overactive reward system in the brain. Longitudinal studies are pivotal for testing these brain-behavior relations because individual slopes are more sensitive for detecting change. The aim of the current study was twofold: (1) to test patterns of age-related change (i.e., linear, quadratic, and cubic) in activity in the nucleus accumbens, a key reward region in the brain, in relation to change in puberty (self-report and testosterone levels), laboratory risk-taking and self-reported risk-taking tendency; and (2) to test whether individual differences in pubertal development and risk-taking behavior were contributors to longitudinal change in nucleus accumbens activity. We included 299 human participants at the first time point and 254 participants at the second time point, ranging between ages 8-27 years, time points were separated by a 2 year interval. Neural responses to rewards, pubertal development (self-report and testosterone levels), laboratory risk-taking (balloon analog risk task; BART), and self-reported risk-taking tendency (Behavior Inhibition System/Behavior Activation System questionnaire) were collected at both time points. The longitudinal analyses confirmed the quadratic age pattern for nucleus accumbens activity to rewards (peaking in adolescence), and the same quadratic pattern was found for laboratory risk-taking (BART). Nucleus accumbens activity change was further related to change in testosterone and self-reported reward-sensitivity (BAS Drive). Thus, this longitudinal analysis provides new insight in risk-taking and reward sensitivity in adolescence: (1) confirming an adolescent peak in nucleus accumbens activity, and (2) underlining a critical role for pubertal hormones and individual differences in risk-taking tendency.

Abnormal Social Reward Responses in Anorexia Nervosa: An fMRI Study

Patients with anorexia nervosa (AN) display impaired social interactions, implicated in the development and prognosis of the disorder. Importantly, social behavior is modulated by reward-based processes, and dysfunctional at-brain-level reward responses have been involved in AN neurobiological models. However, no prior evidence exists of whether these neural alterations would be equally present in social contexts. In this study, we conducted a cross-sectional social-judgment functional magnetic resonance imaging (fMRI) study of 20 restrictive-subtype AN patients and 20 matched healthy controls. Brain activity during acceptance and rejection was investigated and correlated with severity measures (Eating Disorder Inventory -EDI-2) and with personality traits of interest known to modulate social behavior (The Sensitivity to Punishment and Sensitivity to Reward Questionnaire). Patients showed hypoactivation of the dorsomedial prefrontal cortex (DMPFC) during social acceptance and hyperactivation of visual areas during social rejection. Ventral striatum activation during rejection was positively correlated in patients with clinical severity scores. During acceptance, activation of the frontal opercula-anterior insula and dorsomedial/dorsolateral prefrontal cortices was differentially associated with reward sensitivity between groups. These results suggest an abnormal motivational drive for social stimuli, and involve overlapping social cognition and reward systems leading to a disruption of adaptive responses in the processing of social reward. The specific association of reward-related regions with clinical and psychometric measures suggests the putative involvement of reward structures in the maintenance of pathological behaviors in AN.

A new window to understanding individual differences in reward sensitivity from attentional networks

Existing evidence suggests that the presence of reward cues modifies the activity in attentional networks, however, the nature of these influences remains poorly understood. Here, we performed independent component analysis (ICA) in two fMRI datasets corresponding to two incentive delay tasks, which compared the response to reward (money and erotic pictures) and neutral cues, and yielded activations in the ventral striatum using a general linear model approach. Across both experiments, ICA revealed that both the right frontoparietal network and default mode network time courses were positively and negatively modulated by reward cues, respectively. Moreover, this dual neural response pattern was enhanced in individuals with strong reward sensitivity. Therefore, ICA may be a complementary tool to investigate the relevant role of attentional networks on reward processing, and to investigate reward sensitivity in normal and pathological populations.