Largely overlapping neuronal substrates of reactivity to drug, gambling, food and sexual cues: A comprehensive meta-analysis

Anterior Cingulate Cortex in Addiction: New Insights for Neuromodulation

OBJECTIVES

Substance use disorder (SUD) is characterized by compulsive use of addictive substances with considerable impact on both the medical system and society as a whole. The craving of substances leads to relapse in the majority of patients within one year of traditional treatments. In recent decades, neuromodulation approaches have emerged as potential novel treatments of SUD, but the ideal neural target remains contentious.

MATERIALS AND METHODS

In this review, we discuss new insights on the anterior cingulate cortex (ACC) as a neuromodulation target for SUD.

RESULTS AND CONCLUSION

First, we illustrate that the ACC serves as a central "hub" in addiction-related neural networks of cognitive functions, including, but not limited to, decision-making, cognitive inhibition, emotion, and motivation. Then, we summarize the literature targeting the ACC to treat SUDs via available neuromodulation approaches. Finally, we propose potential directions to improve the effect of stimulating the ACC in SUD treatment. We emphasize that the ACC can be divided into at least four sub-regions, which have distinctive functions and connections. Studies focusing on these sub-regions may help to develop more precise and effective ACC stimulation according to patients' symptom profiles and cognitive deficits.

Brain responses to watching food commercials compared with nonfood commercials: a meta-analysis on neuroimaging studies

OBJECTIVE

This study aimed to identify and meta-analyse the neuroimaging data and hence synthesise a brain map showing the neural correlates of watching food commercials.

DESIGN

Published studies were retrieved and included into the analysis if they evaluated brain responses to food commercials with functional MRI and reported results based on whole-brain analysis in standard brain coordinates.

SETTING

No additional restriction was placed on the search, such as the publication year and age of participants.

PARTICIPANTS

Seven papers that composed of a total of 442 participants fulfilled the inclusion criteria. All of them recruited children or adolescents.

RESULTS

Food commercials caused larger brain responses than nonfood counterparts in the cuneus on both hemispheres, which played a role in dietary self-control and modulation of food craving. Other brain regions involved in food commercials processing included the left culmen, left middle occipital gyrus and the right superior parietal lobule, which could be related to reward, emotional responses and habit formation.

CONCLUSION

These neural correlates may help explain the food choice and eating behaviours of children and adolescents that might be relevant to the development of obesity.

Neural correlates of cue reactivity in individuals with smartphone addiction

Popularity of smartphones has dramatically increased in the past years, accompanied by increased concerns regarding potentially adverse effects on physical and mental health. Addictive behavior associated with excessive smartphone use, frequently referred to as "smartphone addiction" (SPA), has attracted increased scientific interest. However the neural correlates of SPA are unknown. We used functional magnetic resonance imaging at 3T to investigate the neural correlates of cue reactivity (CR) in individuals with SPA (n = 21) compared to controls (n = 21). SPA was assessed using the Smartphone Addiction Inventory (SPAI), and neural activity was measured by a modified CR task. Contrasts of images of smartphones vs. neutral stimuli and stimuli including active vs. inactive smartphones (p < 0.001, uncorrected for height, followed by correction for spatial extent) were analyzed. In the first contrast, group differences in medial prefrontal (MPFC), occipital, temporal, and anterior cingulate (ACC) cortices, in temporoparietal regions, and cerebellum were found. For active vs. inactive smartphones, group differences were found in frontal operculum/anterior insula and precentral gyrus. Negative correlations were found between MPFC, ACC, precuneus, and precentral gyrus and specific SPAI subscores, i.e. compulsive behavior, functional impairment and withdrawal. This study suggests spatial similarities of CR-related brain activation between addictive smartphone use and other well-known addictive disorders.

Identification of a brain fingerprint for overweight and obesity

The brain plays a central role in the pathophysiology of overweight and obesity. Connectome-based Predictive Modeling (CPM) is a newly developed, data-driven approach that exploits whole-brain functional connectivity to predict a behavior or trait that varies across individuals. We used CPM to determine whether brain "fingerprints" evoked during milkshake consumption could be isolated for common measures of adiposity in 67 adults with overweight and obesity. We found that CPM captures more variance in waist circumference than either percent body fat or BMI, the most frequently used measures to assess brain correlates of obesity. In a post-hoc analysis, we were also able to derive a largely separable functional connectivity network predicting fasting blood insulin. These findings suggest that, in individuals with overweight and obesity, brain network patterns may be more tightly coupled to waist circumference than BMI or percent body fat and that adiposity and glucose tolerance are associated with distinct maps, pointing to dissociable central pathophysiological phenotypes for obesity and diabetes.

Deficient processing of alcohol cues in the addicted brain: Evidence from event-related potential microstates

OBJECTIVE

Patients with alcohol use disorder (AUD) show altered brain responses to alcohol cues as compared to healthy controls. Event-related potential (ERP) studies mostly focus on the P3, which is usually diminished in AUD patients. The few studies that have investigated earlier components have yielded inconsistent results. The present study aimed at identifying the onset of impaired alcohol cue processing in AUD patients, as well as the association between neurophysiological processing and subjective craving.

METHODS

A sample of 15 inpatients with AUD and 15 healthy controls completed a cue reactivity task with alcohol-related, neutral, and scrambled pictures. Multichannel-EEG was recorded from 70 scalp electrodes, and ERP microstates were analyzed.

RESULTS

Patients displayed impaired neurophysiological processing, as indexed by a weaker P3 and a weaker, insensitive P1. The blunted P1 was associated with higher subjective craving.

CONCLUSIONS

Impaired alcohol cue processing in AUD emerges early, at the stage of sensory processing. Such deficient initial processing seems crucial to understanding cue reactivity processes in the brain and in the subjective experience of craving.

SIGNIFICANCE

The results highlight the importance of investigating early ERP components preceding the P3, and contribute to the debate on the onset of information-processing dysfunction in the addicted brain.

Temporal Dynamics of Large-Scale Networks Predict Neural Cue Reactivity and Cue-Induced Craving

BACKGROUND

Cue reactivity, a core characteristic of substance use disorders, commonly recruits brain regions that are key nodes in neurocognitive networks, including the default mode network (DMN) and salience network (SN). Whether resting-state temporal dynamic properties of these networks relate to subsequent cue reactivity and cue-induced craving is unknown.

METHODS

The resting-state data of 46 nicotine-dependent participants were assessed to define temporal dynamic properties of DMN and SN states. Temporal dynamics focused on the total time across the scan session that brain activity resides in these specific states. Using regression models, we examined how the total time in each state related to neural reactivity to smoking cues within key DMN (posterior cingulate cortex, medial prefrontal cortex) or SN (anterior insula, dorsal anterior cingulate cortex) nodes. Mediation analyses were subsequently conducted to study how neural cue reactivity mediates the relationship between total time in state at rest and subjective cue-induced craving.

RESULTS

Increased time spent in the DMN state and decreased time spent in the SN state predicted subsequent cue-induced increases in the anterior insula and dorsal anterior cingulate cortex, respectively. Cue-induced anterior insula and dorsal anterior cingulate cortex activity significantly mediated the relationship between time spent in DMN/SN and cue-induced subjective craving.

CONCLUSIONS

Our findings showed a significant relationship between resting-state dynamics of the DMN/SN and task-activated SN nodes that together predicted cue-induced craving changes in nicotine-dependent individuals. These findings propose a neurobiological pathway for cue-induced craving that begins with resting-state temporal dynamics, suggesting that brain responding to external stimuli is driven by resting temporal dynamics.

Behavioural cue reactivity to alcohol-related and non-alcohol-related stimuli among individuals with alcohol use disorder: An fMRI study with a visual task

Patients with alcohol use disorder (AUD) have difficulty controlling their alcohol cravings and thus exhibit increased use and early relapse. Although patients tend to respond more strongly to alcohol-related images than to non-alcohol-related images, few researchers have examined the factors that modulate cravings. Here, we examined whole-brain blood oxygen level-dependent (BOLD) responses to behavioural cues in individuals with AUD and in healthy controls (HCs). The participants included 24 patients with AUD and 15 HCs. We presented visual cues consisting of four beverage-related images (juice, drinking juice, sake, and drinking sake), and the cue reactivity of AUD participants was contrasted with that of HC participants. Multiple comparisons revealed that the AUD group had lower BOLD responses than the HC group in the left precuneus (p = 0.036) and the left posterior cingulate cortex (PCC) (p = 0.044) to images of drinking juice and higher BOLD responses than the HC group in the left PCC (p = 0.044) to images of drinking sake. Furthermore, compared to the HCs, the AUD patients had decreased BOLD responses associated with cue reactivity to drinking juice in the left precuneus during the periods from 15 to 18 s (p = 0.004, df = 37) and 18 to 21 s (p = 0.002, df = 37). Our findings suggest that HCs and AUD patients differ in their responses not to images of alcoholic beverages but to images related to alcohol-drinking behaviour. Thus, these patients appear to have different patterns of brain activity. This information may aid clinicians in developing treatments for patients with AUD.

Insights to the neural response to food cues in class III compared with class I and II obese adults using a sample of endometrial cancer survivors seeking weight loss

Background

The rates of severe or Class III obesity (BMI ≥ 40.0 kg/m²) and endometrial cancer (EC) incidence and mortality have been increasing significantly in the United States. Adults with severe obesity are more likely to die and women with severe obesity have a higher risk of EC development and mortality than those with Class I/II obesity (BMI: 30–<40 kg/m²). However, no prior studies have evaluated the neural response to food cues by obesity severity/class in adults with or without cancer.

Methods

We conducted a functional magnetic resonance imaging visual food cue task in 85 obese Stage I EC survivors who were seeking weight loss in a lifestyle intervention at baseline. We evaluated the neural response to high-calorie vs. non-food images after an overnight fast (fasted state) and after eating a standardized meal (fed state), and grouped patients by obesity class (Class I/II: n = 38; Class III: n = 47).

Results

In the fasted state, we found increased activation in several regions including the dorsolateral prefrontal cortex (DLPFC) in Class III and Class I/II patients (whole brain cluster corrected (WBCC), p < 0.05), which was significantly higher in Class III vs. Class I/II (p < 0.05). We found decreased activation in the insula in the fasted state, which was significantly lower in Class I/II vs. Class III (p = 0.03). In the fed state, we found increased activation in the DLPFC in Class III and Class I/II (WBCC, p < 0.05). The increased activation in cognitive control/inhibition regions (DLPFC) is consistent with the summative literature; however, the decreased activation in taste information processing regions (insula) was unexpected.

Conclusions

Our results provide novel insights on food cue response between different classes of obesity and highlight the importance of targeting the DLPFC in weight loss interventions, particularly in severely obese patients. Additional studies examining food-related neural circuitry between different classes of obesity are needed.

After the Honeymoon: Neural and Genetic Correlates of Romantic Love in Newlywed Marriages

In Western culture, romantic love is commonly a basis for marriage. Although it is associated with relationship satisfaction, stability, and individual well-being, many couples experience declines in romantic love. In newlyweds, specifically, changes in love predict marital outcomes. However, the biological mechanisms underlying the critical transition to marriage are unknown. Thus, for the first time, we explored the neural and genetic correlates of romantic love in newlyweds. Nineteen first-time newlyweds were scanned (with functional MRI) while viewing face images of the partner versus a familiar acquaintance, around the time of the wedding (T1) and 1 year after (T2). They also provided saliva samples for genetic analysis (AVPR1a rs3, OXTR rs53576, COMT rs4680, and DRD4-7R), and completed self-report measures of relationship quality including the Eros (romantic love) scale. We hypothesized that romantic love is a developed form of the mammalian drive to find, and keep, preferred mates; and that its maintenance is orchestrated by the brain's reward system. Results showed that, at both time points, romantic love maintenance (Eros difference score: T2-T1) was associated with activation of the dopamine-rich substantia nigra in response to face images of the partner. Interactions with vasopressin, oxytocin, and dopamine genes implicated in pair-bonding (AVPR1a rs3, OXTR rs53576, COMT rs4680, and DRD4-7R) also conferred strong activation in the dopamine-rich ventral tegmental area at both time points. Consistent with work highlighting the role of sexual intimacy in relationships, romantic love maintenance showed correlations in the paracentral lobule (genital region) and cortical areas involved in sensory and cognitive processing (occipital, angular gyrus, insular cortex). These findings suggest that romantic love, and its maintenance, are orchestrated by dopamine-, vasopressin- and oxytocin-rich brain regions, as seen in humans and other monogamous animals. We also provide genetic evidence of polymorphisms associated with oxytocin, vasopressin and dopamine function that affect the propensity to sustain romantic love in early stage marriages. We conclude that romantic love maintenance is part of a broad mammalian strategy for reproduction and long-term attachment that is influenced by basic reward circuitry, complex cognitive processes, and genetic factors.

Endocannabinoid LTD in Accumbal D1 Neurons Mediates Reward-Seeking Behavior

The nucleus accumbens (NAc) plays a key role in drug-related behavior and natural reward learning. Synaptic plasticity in dopamine D1 and D2 receptor medium spiny neurons (MSNs) of the NAc and the endogenous cannabinoid (eCB) system have been implicated in reward seeking. However, the precise molecular and physiological basis of reward-seeking behavior remains unknown. We found that the specific deletion of metabotropic glutamate receptor 5 (mGluR5) in D1-expressing MSNs (D1^miRmGluR5 mice) abolishes eCB-mediated long-term depression (LTD) and prevents the expression of drug (cocaine and ethanol), natural reward (saccharin), and brain-stimulation-seeking behavior. In vivo enhancement of 2-arachidonoylglycerol (2-AG) eCB signaling within the NAc core restores both eCB-LTD and reward-seeking behavior in D1^miRmGluR5 mice. The data suggest a model where the eCB and glutamatergic systems of the NAc act in concert to mediate reward-seeking responses.

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mGluR5-D1-CB1-induced eCB-LTD mediates drugs of abuse and natural reward seeking

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eCB-LTD in D2-MSNs plays no important role in processing of reward-seeking responses

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Loss of eCB-LTD is a consequence of higher MAGL activity and lower CB1R expression

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Acute drug administration stops craving for alternative rewards on following days

Women at Greater Sexual Risk for STIs/HIV Have a Lower Mesolimbic and Affective Bias Response to Sexual Stimuli

Young adult women in the United States have high rates of sexually transmitted infections, increasing the risk of human immunodeficiency virus (HIV). The underlying neurobiology of behaviors that increase the probability of contracting sexually-transmitted diseases (STIs) and HIV is just beginning to be explored. The current study assessed the link between sexual risk and the brain and behavioral response to sexual cues in emerging adult women. Our hypothesis was that women with more activity in reward/motivational circuitry would report higher sexual risk behaviors and would evidence higher positive affective bias to visual sexual stimuli. Women (n = 52; age = 18–24 years) who had protected sex 100% of the time (n = 17) vs. those who did not (n = 35), in the past 3 months, were compared on their brain response to 500 ms evocative (sex, aversive, food) vs. neutral cues in a blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) fast event-related design. Based on existing literature, an a priori anatomical “cue-reactive” mask was used to constrain the analyses. Self-reported sexual activity and the affective bias scores to sexual cues were examined as correlates with the brain response to cues. In contrast to our initial hypothesis, the higher sexual risk (Unprotected) group had significantly less activation in mesolimbic brain regions and lower (less positive) affective bias scores to sexual cues compared to the lower risk (Protected) group. As predicted, the brain response was positively correlated with sexual bias. Follow-up analyses showed an effect of partner “risk” (e.g., more vs. less knowledge of partner’s STIs/HIV status). This evidence suggests that women who have protected sex may view sexual-related stimuli more positively, reflected by a neural response in reward/motivational regions and more positive sexual bias scores. In contrast, young women at increased risk for STIs/HIV may feel more negatively about sexual-related stimuli, evidenced by a lower mesolimbic response and a less positive affective bias to sexual cues. These data may help identify young women who are at greatest risk for acquiring STIs and/or HIV, which carries added importance with the availability of new medications that can prevent HIV.

Incubation of neural alcohol cue reactivity after withdrawal and its blockade by naltrexone

During the first weeks of abstinence, alcohol craving in patients may increase or "incubate." We hypothesize that Naltrexone (NTX) blocks this incubation effect. Here, we compared NTX effects on neural alcohol cue reactivity (CR) over the first weeks of abstinence and on long-term clinical outcomes to standard treatment. Male alcohol-dependent patients (n = 55) and healthy controls (n = 35) were enrolled. Participants underwent baseline psychometric testing and functional magnetic resonance imaging (fMRI) assessment of mesolimbic alcohol CR. Patients participated in a standard treatment program with the option of adjuvant NTX. They received another scan after 2 weeks of treatment. We found higher CR in several brain regions in patients versus healthy controls. CR significantly increased over 2 weeks in the standard treatment group (n = 13) but not in the NTX group (n = 22). NTX significantly attenuated CR in the left putamen and reduced relapse risk to heavy drinking within 3 months of treatment. Additionally, increased CR in the left putamen and its course over time predicted both NTX response and relapse risk. Carrier status for the functional OPRM1 variant rs1799971:A > G was considered but had no effect on NTX efficacy. In conclusion, NTX was most effective in patients with high CR in the left putamen. While the results from our naturalistic study await further confirmation from prospective randomized trials, they support a potential role of neural CR as a biomarker in the development of precision medicine approaches with NTX.

Dysfunctional attentional bias and inhibitory control during anti-saccade task in patients with internet gaming disorder: An eye tracking study

BACKGROUND

Although internet gaming disorder (IGD) is considered an addictive disorder, evidence of the neurobiological underpinnings of IGD as an addictive disorder is currently lacking. We investigated whether attentional bias toward game-related stimuli was altered in IGD patients using an eye-tracking method during an anti-saccade task.

METHODS

Twenty-three IGD patients and 27 healthy control (HC) subjects participated in the anti-saccade task with game-related, neutral, and scrambled images during eye tracking. Participants rated subjective scores of valence, arousal, and craving for each image stimulus after finishing eye tracking. Mixed design analysis of variance was performed to compare the differences between eye movement latency and error rate in the pro-saccade and anti-saccade conditions according to image type across the IGD and HC groups.

RESULTS

In the anti-saccade task, the IGD group exhibited higher error rates in the case of game-related images than in neutral or scrambled images. However, ratings on valence, arousal, and craving did not vary among image types. The error rates of the HCs did not vary across image types, but higher arousal/craving and lower valence were reported with respect to the game-related images.

CONCLUSIONS

Increased error rate during anti-saccade tasks with game-related stimuli in IGD may be due to disabilities in goal-directed behavior or inhibitory control, as observed in other addictive disorders. These findings suggest that attentional bias toward game-related stimuli can be a sensitive biological marker of IGD as an addictive disorder.

Bouncing back: Brain rehabilitation amid opioid and stimulant epidemics

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Frontoparietal event related potentials predict/track recovery.

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Frontostriatal functional magnetic resonance imaging signals predict/track recovery.

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Transcranial magnetic left prefrontal stimulation reduces craving and drug use.

Recent methamphetamine and opioid use epidemics are a major public health concern. Chronic stimulant and opioid use are characterized by significant psychosocial, physical and mental health costs, repeated relapse, and heightened risk of early death. Neuroimaging research highlights deficits in brain processes and circuitry that are linked to responsivity to drug cues over natural rewards as well as suboptimal goal-directed decision-making. Despite the need for interventions, little is known about (1) how the brain changes with prolonged abstinence or as a function of various treatments; and (2) how symptoms change as a result of neuromodulation. This review focuses on the question: What do we know about changes in brain function during recovery from opioids and stimulants such as methamphetamine and cocaine? We provide a detailed overview and critique of published research employing a wide array of neuroimaging methods – functional and structural magnetic resonance imaging, electroencephalography, event-related potentials, diffusion tensor imaging, and multiple brain stimulation technologies along with neurofeedback – to track or induce changes in drug craving, abstinence, and treatment success in stimulant and opioid users. Despite the surge of methamphetamine and opioid use in recent years, most of the research on neuroimaging techniques for recovery focuses on cocaine use. This review highlights two main findings: (1) interventions can lead to improvements in brain function, particularly in frontal regions implicated in goal-directed behavior and cognitive control, paired with reduced drug urges/craving; and (2) the targeting of striatal mechanisms implicated in drug reward may not be as cost-effective as prefrontal mechanisms, given that deep brain stimulation methods require surgery and months of intervention to produce effects. Overall, more studies are needed to replicate and confirm findings, particularly for individuals with opioid and methamphetamine use disorders.

Developing neuroscience-based treatments for alcohol addiction: A matter of choice?

Excessive alcohol use is the cause of an ongoing public health crisis, and accounts for ~5% of global disease burden. A minority of people with recreational alcohol use develop alcohol addiction (hereafter equated with "alcohol dependence" or simply "alcoholism"), a condition characterized by a systematically biased choice preference for alcohol at the expense of healthy rewards, and continued use despite adverse consequences ("compulsivity"). Alcoholism is arguably the most pressing area of unmet medical needs in psychiatry, with only a small fraction of patients receiving effective, evidence-based treatments. Medications currently approved for the treatment of alcoholism have small effect sizes, and their clinical uptake is negligible. No mechanistically new medications have been approved since 2004, and promising preclinical results have failed to translate into novel treatments. This has contributed to a reemerging debate whether and to what extent alcohol addiction represents a medical condition, or reflects maladaptive choices without an underlying brain pathology. Here, we review this landscape, and discuss the challenges, lessons learned, and opportunities to retool drug development in this important therapeutic area.

Addiction and the Dark Triad of Personality

In this article, we review associations between the Dark Triad of personality (narcissism, Machiavellianism, and psychopathy) and addictive behaviors, both substance-related and non-substance-related. We summarize evidence from personality and clinical research and integrate it with prevailing models of addiction. Specifically, we discuss addictive behavior in the light of affect regulation, which is likely more relevant in narcissism, as well as inhibitory deficits, a putative mechanism in psychopathy. These mechanisms can be related to central motives of the respective personality constructs, such as stabilization of self-esteem in narcissism and impulsive stimulation seeking in psychopathy. We conclude that different mechanisms might lead to similar observable behavior in narcissism and psychopathy at earlier stages of the addiction cycle, but psychopathic disinhibition might be particularly relevant at later stages. This underpins the importance of considering personality factors for the understanding and treatment of addiction.

Examining neural reactivity to gambling cues in the age of online betting

Purpose of Review

The goal of this review is to provide new insights as to how and why functional magnetic resonance imaging (fMRI) research on gambling cue reactivity can contribute to significant progress towards the understanding of gambling disorder. After having offered a detailed description of experimental paradigms and a comprehensive summary of findings related to gambling cue reactivity, the present review suggests methodological avenues for future research.

Recent Findings

The fMRI literature on problem gambling has identified the main neural pathways associated with reactivity to gambling cues. Yet, the current knowledge on the key factors underlying cue reactivity in gambling is still very incomplete. Here, we suggest that the recent expansion of online sports betting calls for a new line of research offering a fine-grained and up-to-date approach of neural cue reactivity in gambling disorder.

Summary

Experimental designs that investigate individual-specific and study-specific factors related to sports betting have the potential to foster progress towards efficient treatment and prevention of gambling disorder.

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.

Brain response features during forced break could predict subsequent recovery in internet gaming disorder: A longitudinal study

Although internet gaming disorder (IGD) is associated with negative health measures, individuals may recover without professional intervention. Exploring neural features associated with natural recovery may provide insights into how best to promote health among people with IGD. Seventy-nine IGD subjects were scanned when they were performing cue-craving tasks before and after gaming was interrupted with a forced break. After one year, 20 individuals no longer met IGD criteria and were considered recovered. We compared brain responses in cue-craving tasks between these 20 recovered IGD subjects and 20 matched IGD subjects still meeting criteria at one year (persistent IGD). Recovered IGD subjects showed lower dorsolateral prefrontal cortex (DLPFC) activation than persistent IGD subjects to gaming cues at both pre- and post-gaming times. Significant group-by-time interactions were found in the bilateral DLPFC and insula, and these involved relatively decreased DLPFC and increased insula activation in the persistent IGD group during the forced break. Relatively decreased DLPFC activity and increased insula activity in response to gaming cues following recent gaming may underlie persistence of gaming. These findings suggest that executive control and interoceptive processing warrant additional study in understanding recovery from IGD.

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.

Cue Reactivity in the Ventral Striatum Characterizes Heavy Cannabis Use, Whereas Reactivity in the Dorsal Striatum Mediates Dependent Use

BACKGROUND

Animal models of addiction suggest that the transition from incentive-driven drug use to habitual and ultimately compulsive drug use is mediated by a shift from ventral to dorsal striatal cue control over drug seeking. Previous studies in human cannabis users reported elevated trait impulsivity and neural cue reactivity in striatal circuits; however, these studies were not able to separate addiction-related from exposure-related adaptations.

METHODS

To differentiate the adaptive changes, the current functional magnetic resonance imaging study examined behavioral and neural cue reactivity in dependent (n = 18) and nondependent (n = 20) heavy cannabis users and a nonusing reference group (n = 44).

RESULTS

Irrespective of dependence status, cannabis users demonstrated elevated trait impulsivity as well as increased ventral striatal reactivity and striatal frontal coupling in response to drug cues. Dependent users selectively exhibited dorsal striatal reactivity and decreased striatal limbic coupling during cue exposure. An exploratory analysis revealed that higher ventral caudate neural cue reactivity was associated with stronger cue-induced arousal and craving in dependent users, whereas this pattern was reversed in nondependent users.

CONCLUSIONS

Taken together, the current findings suggest that exaggerated responses of the ventral striatal reward system may promote excessive drug use in humans, whereas adaptations in dorsal striatal systems engaged in habit formation may promote the transition to addictive use.

Missing motoric manipulations: rethinking the imaging of the ventral striatum and dopamine in human reward

Human neuroimaging studies of natural rewards and drugs of abuse frequently assay the brain's response to stimuli that, through Pavlovian learning, have come to be associated with a drug's rewarding properties. This might be characterized as a 'sensorial' view of the brain's reward system, insofar as the paradigms are designed to elicit responses to a reward's (drug's) sight, aroma, or flavor. A different field of research nevertheless suggests that the mesolimbic dopamine system may also be critically involved in the motor behaviors provoked by such stimuli. This brief review and commentary surveys some of the preclinical data supporting this more "efferent" (motoric) view of the brain's reward system, and discusses what such findings might mean for how human brain imaging studies of natural rewards and drugs of abuse are designed.

Increasing Chocolate's Sugar Content Enhances Its Psychoactive Effects and Intake

Chocolate elicits unique brain activity compared to other foods, activating similar brain regions and neurobiological substrates with potentially similar psychoactive effects as substances of abuse. We sought to determine the relationship between chocolate with varying combinations of its main constituents (sugar, cocoa, and fat) and its psychoactive effects. Participants consumed 5 g of a commercially available chocolate with increasing amounts of sugar (90% cocoa, 85% cocoa, 70% cocoa, and milk chocolates). After each chocolate sample, participants completed the Psychoactive Effects Questionnaire (PEQ). The PEQ consists of questions taken from the Morphine-Benzedrine Group (MBG), Morphine (M,) and Excitement (E) subscales of the Addiction Research Center Inventory. After all testing procedures, participants completed the Binge Eating Scale (BES) while left alone and allowed to eat as much as they wanted of each of the different chocolates. We found a measurable psychoactive dose⁻effect relationship with each incremental increase in the chocolate's sugar content. The total number of positive responses and the number of positive responses on the E subscale began increasing after tasting the 90% cocoa chocolate, whereas the number of positive responses on the MBG and M subscales began increasing after tasting the 85% cocoa chocolate sample. We did not find a correlation between BES scores and the total amount of chocolate consumed or self-reported scores on the PEQ. These results suggest that each incremental increase in chocolate's sugar content enhances its psychoactive effects. These results extend our understanding of chocolate's appeal and unique ability to prompt an addictive-like eating response.

Quantitative evaluation of cue-induced reinstatement model for evidence-based experimental optimization

Cue-induced reinstatement is a widely used model for investigating relapse of reward-seeking behavior with high face validity in relation to clinical observations. Yet, face validity is not sufficient to evaluate an animal model, and quantitative, evidence-based analysis is required to estimate the ultimate applicability of this paradigm. Furthermore, such analysis would allow an accurate and reproducible design of future experiments. Here, we conducted meta-analysis and cluster analysis to characterize the impact of cue type (visual, auditory, olfactory or combinations thereof), intensity (e.g. light frequency, sound volume and odor concentration), reward type (e.g. different drugs of abuse, sucrose and food pellets) and model parameters (e.g. housing condition, age, gender and strain of animals) on reinstatement levels. We selected 184 publications for meta-analysis based on inclusion criteria with a total number of 3889 rats. Our analysis suggested that the exact level of reinstatement depends on neither cue type, nor intensity nor on the type of reward. While all cues induced reinstatement to reward-seeking behavior, it is the model parameters, in particular, the housing conditions, age and strain, that defined the final reinstatement levels. In particular, single-housed, adolescent, Wistar or Lister Hooded rats showed significantly higher reinstatement than adult, Sparague-Dawley rats housed in groups. Our findings suggest that model parameters (for example, single housing) evoke stress-induced behaviors that affect reinstatement more than cue/reward factors.

Prospective changes in neural alcohol cue reactivity in at-risk adolescents

Adolescence represents an ideal time for elucidating the etiology of cue reactivity profiles. This study examined the influence of three risk factors consistently associated with heavy adolescent drinking on alcohol cue reactivity. Youth were first assessed while still naïve to alcohol (12-14 years old) and followed after transitioning into alcohol use (17-21 years old). The effects of family history of substance use disorder, sex, and history of early of dating (i.e., before 14 years of age) on BOLD response contrast to alcohol picture cues were examined in a linear mixed model, controlling for age and alcohol use patterns at follow-up. Activation to alcohol picture cues differed as a function of risk factor and time. At baseline, family history positive youth showed greater activation to alcohol cues than family history negative peers in the right middle occipital and anterior cingulate gyri. Youth with a history of early-dating showed greater activation to alcohol cues, compared to non-early daters, in the left anterior cingulate/white matter region. Girls showed greater activation to alcohol than boys at baseline in left middle frontal gyrus. At follow-up, after drinking started, patterns reversed for each risk factor. These results indicate that even prior to initiating alcohol use, adolescents showed differences in activation to alcohol cues based on their family history, dating history, and sex.

Investigating a novel fMRI cannabis cue reactivity task in youth

OBJECTIVE

Adult and adolescent studies suggest increased motivational responses to cannabis cues among regular cannabis users. However, functional magnetic resonance imaging (fMRI) studies have not explored neural activation in response to visual cannabis cues among adolescents in the United States. Gaining a better understanding of the neural circuits related to cue-elicited craving during adolescence may shed light on the neural basis for the development of problematic cannabis use that could ultimately be targeted for interventions.

METHODS

41 non-treatment-seeking youth (ages 17-21; mean age = 18.83; 46.3% female) who reported regular cannabis use underwent fMRI scanning involving a visual cannabis cue task and completed self-report and biological measures. Whole-brain activation was examined for cannabis cues compared to non-cannabis cues, and for active versus passive cannabis cues. Associations between self-reported substance use and task activation were examined.

RESULTS

Cannabis images were identifiable to adolescents and were rated as more rewarding than matched non-cannabis images (p < .05). Greater activation was found for the cannabis cues compared to non-cannabis cues in bilateral posterior cingulate, cuneus, fusiform, precuneus, inferior temporal and parahippocampal gyri, as well as left thalamus, medial frontal and superior frontal gyri. Cue-elicited activation was not significantly associated with self-reported cannabis use (ps > 0.05). No differences were observed for the active versus passive cue contrast.

CONCLUSIONS

Cannabis-using youth show more activation to cannabis cues than non-cannabis cues in brain regions underlying incentive salience, reward, and visual attention. This task could be useful for future studies examining neural underpinnings of reward processes in adolescent cannabis users.

Resonance-Paced Breathing Alters Neural Response to Visual Cues: Proof-of-Concept for a Neuroscience-Informed Adjunct to Addiction Treatments

Conscious attempts to regulate alcohol and drug use are often undermined by automatic attention and arousal processes that are activated in the context of salient cues. Response to these cues involves body and brain signals that are linked via dynamic feedback loops, yet no studies have targeted the cardiovascular system as a potential conduit to alter automatic neural processes that maintain cue salience. This proof-of-concept study examined within-person changes in neural response to parallel but unique sets of visual alcohol-related cues at two points in time: prior to versus following a brief behavioral intervention. The active intervention was resonance breathing, a rhythmical breathing task paced at 0.1 Hz (6 breaths per minute) that helps normalize neurocardiac feedback. The control intervention was a low-demand cognitive task. Functional magnetic resonance imaging (fMRI) was used to assess changes in brain response to the cues presented before (A1) and after (A2) the intervention in 41 emerging adult men and women with varying drinking behaviors. The resonance breathing group exhibited significantly less activation to A2 cues compared with A1 cues in left inferior and superior lateral occipital cortices, right inferior lateral occipital cortex, bilateral occipital pole, and temporal occipital fusiform cortices. This group also showed significantly greater activation to A2 cues compared with A1 cues in medial prefrontal, anterior and posterior cingulate, and precuneus cortices, paracingulate, and lingual gyri. The control group showed no significant changes. Thus, following resonance breathing, activation in brain regions involved in visual processing of cues was reduced, while activation in brain areas implicated in behavioral control, internally directed cognition, and brain-body integration was increased. These findings provide preliminary evidence that manipulation of the cardiovascular system with resonance breathing alters neural activation in a manner theoretically consistent with a dampening of automatic sensory input and strengthening of higher-level cognitive processing.

Alcohol Expectancy and Cerebral Responses to Cue-Elicited Craving in Adult Nondependent Drinkers

BACKGROUND

Positive alcohol expectancy (AE) contributes to excessive drinking. Many imaging studies have examined cerebral responses to alcohol cues and how these regional processes related to problem drinking. However, it remains unclear how AE relates to cue response and whether AE mediates the relationship between cue response and problem drinking.

METHODS

A total of 61 nondependent drinkers were assessed with the Alcohol Expectancy Questionnaire and Alcohol Use Disorder Identification Test and underwent functional magnetic resonance imaging while exposed to alcohol and neutral cues. Imaging data were processed and analyzed with published routines, and mediation analyses were conducted to examine the interrelationships among global positive score of the Alcohol Expectancy Questionnaire, Alcohol Use Disorder Identification Test score, and regional responses to alcohol versus neutral cues.

RESULTS

Alcohol as compared with neutral cues engaged the occipital, retrosplenial, and medial orbitofrontal cortex as well as the left caudate head and red nucleus. The bilateral thalamus showed a significant correlation in cue response and in left superior frontal cortical connectivity with global positive score in a linear regression. Mediation analyses showed that global positive score completely mediated the relationship between thalamic cue activity as well as superior frontal cortical connectivity and Alcohol Use Disorder Identification Test score. The alternative models that AE contributed to problem drinking and, in turn, thalamic cue activity and connectivity were not supported.

CONCLUSIONS

The findings suggest an important role of the thalamic responses to alcohol cues in contributing to AE and at-risk drinking in nondependent drinkers. AEs may reflect a top-down modulation of the thalamic processing of alcohol cues, influencing the pattern of alcohol use.

Prefronto-cerebellar neuromodulation affects appetite in obesity

Human neuroimaging studies have consistently reported changes in cerebellar function and integrity in association with obesity. To date, however, the nature of this link has not been studied directly. Emerging evidence suggests a role for the cerebellum in higher cognitive functions through reciprocal connections with the prefrontal cortex. The purpose of this exploratory study was to examine appetite changes associated with noninvasive prefronto-cerebellar neuromodulation in obesity. 12 subjects with class I obesity (mean BMI 32.9 kg/m²) underwent a randomized, single-blinded, sham-controlled, crossover study, during which they received transcranial direct current stimulation (tDCS; active/sham) aimed at simultaneously enhancing the activity of the prefrontal cortex and decreasing the activity of the cerebellum. Changes in appetite (state and food-cue-triggered) and performance in a food-modified working memory task were evaluated. We found that active tDCS caused an increase in hunger and desire to eat following food-cue exposure. In line with these data, subjects also tended to make more errors during the working memory task. No changes in basic motor performance occurred. This study represents the first demonstration that prefronto-cerebellar neuromodulation can influence appetite in individuals with obesity. While preliminary, our findings support a potential role for prefronto-cerebellar pathways in the behavioral manifestations of obesity.

Hedonic processing in humans is mediated by an opioidergic mechanism in a mesocorticolimbic system

It has been hypothesized that the pleasure of a reward in humans is mediated by an opioidergic system involving the hypothalamus, nucleus accumbens and the amygdala. Importantly, enjoying the pleasure of a reward is distinct from incentive salience induced by cues predicting the reward. We investigated this issue using a within subject, pharmacological challenge design with the opioid receptor antagonist naloxone and fMRI. Our data show that blocking opioid receptors reduced pleasure associated with viewing erotic pictures more than viewing symbols of reward such as money. This was paralleled by a reduction of activation in the ventral striatum, lateral orbitofrontal cortex, amygdala, hypothalamus and medial prefrontal cortex. Crucially, the naloxone induced activation decrease was observed at reward delivery, but not during reward anticipation, indicating that blocking opioid receptors decreases the pleasure of rewards in humans.

Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).

Competing Motivations: Proactive Response Inhibition Toward Addiction-Related Stimuli in Quitting-Motivated Individuals

We examined whether addiction-related cues impact proactive inhibition (the restraint of actions in preparation for stopping) in individuals who are motivated to quit gambling or cannabis use. In Study 1, treatment-seeking individuals with cannabis use disorder and matched controls performed a stop-signal task that required them to inhibit categorizing cannabis or neutral pictures, and within varying levels of stop-signal probability. In Study 2, two groups of individuals, who applied to a voluntary self-exclusion program toward gambling, performed the stop-task following relaxation or gambling craving induction, with results compared to non-gamblers. Study 1 showed that despite being less efficient in proactive inhibition, individuals with cannabis use disorder exhibited heightened proactive inhibition toward cannabis cues. In Study 2, proactive inhibition toward gambling cues was heightened in gamblers after craving, but the degree of proactive adjustment decreased as a function of induced changes in gambling-related motivation. Present findings demonstrate that exposure to addiction-related cues can modulate proactive inhibition in individuals who are motivated to restrict their addictive behaviors.

G protein-coupled receptor heteromers are key players in substance use disorder

G protein-coupled receptors (GPCR) represent the largest family of membrane proteins in the human genome. Physical association between two different GPCRs is linked to functional interactions which generates a novel entity, called heteromer, with specific ligand binding and signaling properties. Heteromerization is increasingly recognized to take place in the mesocorticolimbic pathway and to contribute to various aspects related to substance use disorder. This review focuses on heteromers identified in brain areas relevant to drug addiction. We report changes at the molecular and cellular levels that establish specific functional impact and highlight behavioral outcome in preclinical models. Finally, we briefly discuss selective targeting of native heteromers as an innovative therapeutic option.

Animal models of addiction

In recent years, animal models in psychiatric research have been criticized for their limited translational value to the clinical situation. Failures in clinical trials have thus often been attributed to the lack of predictive power of preclinical animal models. Here, I argue that animal models of voluntary drug intake—under nonoperant and operant conditions—and addiction models based on the Diagnostic and Statistical Manual of Mental Disorders are crucial and informative tools for the identification of pathological mechanisms, target identification, and drug development. These models provide excellent face validity, and it is assumed that the neurochemical and neuroanatomical substrates involved in drug-intake behavior are similar in laboratory rodents and humans. Consequently, animal models of drug consumption and addiction provide predictive validity. This predictive power is best illustrated in alcohol research, in which three approved medications—acamprosate, naltrexone, and nalmefene—were developed by means of animal models and then successfully translated into the clinical situation.

Cue-reactivity in behavioral addictions: A meta-analysis and methodological considerations

Background and aims Recent research has applied cue-reactivity paradigms to behavioral addictions. The aim of the current meta-analysis is to systematically analyze the effects of learning-based cue-reactivity in behavioral addictions. Methods The current meta-analysis includes 18 studies (29 data sets, 510 participants) that have used a cue-reactivity paradigm in persons with gambling (eight studies), gaming (nine studies), or buying (one study) disorders. We compared subjective, peripheral physiological, electroencephal, and neural responses toward addiction-relevant cues in patients versus control participants and toward addiction-relevant cues versus control cues in patients. Results Persons with behavioral addictions showed higher cue-reactivity toward addiction-relevant cues compared with control participants: subjective cue-reactivity (d = 0.84, p = .01) and peripheral physiological and electroencephal measures of cue-reactivity (d = 0.61, p < .01). Increased neural activation was found in the caudate nucleus, inferior frontal gyrus, median cingulate cortex, subgenual cingulate, and precentral gyrus. Persons with gambling, gaming, or buying disorders also showed higher cue-reactivity toward addiction-relevant cues compared with control cues: subjective cue-reactivity (d = 0.39, p = .11) and peripheral physiological and electroencephal measures of cue-reactivity (d = 0.47, p = .05). Increased neural activation was found in the caudate nucleus, inferior frontal gyrus, angular gyrus, inferior network, and precuneus. Discussion and conclusions Cue-reactivity not only exists in substance-use disorders but also in gambling, gaming, and buying disorders. Future research should differentiate between cue-reactivity in addictive behaviors and cue-reactivity in functional excessive behaviors such as passions, hobbies, or professions.

Closed Loop Deep Brain Stimulation for PTSD, Addiction, and Disorders of Affective Facial Interpretation: Review and Discussion of Potential Biomarkers and Stimulation Paradigms

The treatment of psychiatric diseases with Deep Brain Stimulation (DBS) is becoming more of a reality as studies proliferate the indications and targets for therapies. Opinions on the initial failures of DBS trials for some psychiatric diseases point to a certain lack of finesse in using an Open Loop DBS (OLDBS) system in these dynamic, cyclical pathologies. OLDBS delivers monomorphic input into dysfunctional brain circuits with modulation of that input via human interface at discrete time points with no interim modulation or adaptation to the changing circuit dynamics. Closed Loop DBS (CLDBS) promises dynamic, intrinsic circuit modulation based on individual physiologic biomarkers of dysfunction. Discussed here are several psychiatric diseases which may be amenable to CLDBS paradigms as the neurophysiologic dysfunction is stochastic and not static. Post-Traumatic Stress Disorder (PTSD) has several peripheral and central physiologic and neurologic changes preceding stereotyped hyper-activation behavioral responses. Biomarkers for CLDBS potentially include skin conductance changes indicating changes in the sympathetic nervous system, changes in serum and central neurotransmitter concentrations, and limbic circuit activation. Chemical dependency and addiction have been demonstrated to be improved with both ablation and DBS of the Nucleus Accumbens and as a serendipitous side effect of movement disorder treatment. Potential peripheral biomarkers are similar to those proposed for PTSD with possible use of environmental and geolocation based cues, peripheral signs of physiologic arousal, and individual changes in central circuit patterns. Non-substance addiction disorders have also been serendipitously treated in patients with OLDBS for movement disorders. As more is learned about these behavioral addictions, DBS targets and effectors will be identified. Finally, discussed is the use of facial recognition software to modulate activation of inappropriate responses for psychiatric diseases in which misinterpretation of social cues feature prominently. These include Autism Spectrum Disorder, PTSD, and Schizophrenia-all of which have a common feature of dysfunctional interpretation of facial affective clues. Technological advances and improvements in circuit-based, individual-specific, real-time adaptable modulation, forecast functional neurosurgery treatments for heretofore treatment-resistant behavioral diseases.