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

Appetitive conditioning with pornographic stimuli elicits stronger activation in reward regions than monetary and gaming-related stimuli

Appetitive conditioning plays an important role in the development and maintenance of pornography-use and gaming disorders. It is assumed that primary and secondary reinforcers are involved in these processes. Despite the common use of pornography and gaming in the general population appetitive conditioning processes in this context are still not well studied. This study aims to compare appetitive conditioning processes using primary (pornographic) and secondary (monetary and gaming-related) rewards as unconditioned stimuli (UCS) in the general population. Additionally, it investigates the conditioning processes with gaming-related stimuli as this type of UCS was not used in previous studies. Thirty-one subjects participated in a differential conditioning procedure in which four geometric symbols were paired with either pornographic, monetary, or gaming-related rewards or with nothing to become conditioned stimuli (CS + porn, CS + game, CS + money, and CS-) in an functional magnetic resonance imaging study. We observed elevated arousal and valence ratings as well as skin conductance responses for each CS+ condition compared to the CS-. On the neural level, we found activations during the presentation of the CS + porn in the bilateral nucleus accumbens, right medial orbitofrontal cortex, and the right ventral anterior cingulate cortex compared to the CS-, but no significant activations during CS + money and CS + game compared to the CS-. These results indicate that different processes emerge depending on whether primary and secondary rewards are presented separately or together in the same experimental paradigm. Additionally, monetary and gaming-related stimuli seem to have a lower appetitive value than pornographic rewards.

Large-scale network abnormality in behavioral addiction

BACKGROUND

Researchers have endeavored to ascertain the network dysfunction associated with behavioral addiction (BA) through the utilization of resting-state functional connectivity (rsFC). Nevertheless, the identification of aberrant patterns within large-scale networks pertaining to BA has proven to be challenging.

METHODS

Whole-brain seed-based rsFC studies comparing subjects with BA and healthy controls (HC) were collected from multiple databases. Multilevel kernel density analysis was employed to ascertain brain networks in which BA was linked to hyper-connectivity or hypo-connectivity with each prior network.

RESULTS

Fifty-six seed-based rsFC publications (1755 individuals with BA and 1828 HC) were included in the meta-analysis. The present study indicate that individuals with BAs exhibit (1) hypo-connectivity within the fronto-parietal network (FN) and hypo- and hyper-connectivity within the ventral attention network (VAN); (2) hypo-connectivity between the FN and regions of the VAN, hypo-connectivity between the VAN and regions of the FN and default mode network (DMN), hyper-connectivity between the DMN and regions of the FN; (3) hypo-connectivity between the reward system and regions of the sensorimotor network (SS), DMN and VAN; (4) hypo-connectivity between the FN and regions of the SS, hyper-connectivity between the VAN and regions of the SS.

CONCLUSIONS

These findings provide impetus for a conceptual framework positing a model of BA characterized by disconnected functional coordination among large-scale networks.

Sex differences of neural connectivity in internet gaming disorder and its association with sleep quality: an exploratory fMRI study

Objectives

Sex-specific differences in internet gaming disorder (IGD) neurophysiology remain underexplored. Here we investigated sex-related variability in regional homogeneity (ReHo) and functional connectivity (FC) in IGD and their correlations with sleep quality.

Methods

Resting-state functional magnetic resonance imaging (fMRI) scans were performed on 52 subjects with IGD and 50 healthy controls (HCs). Two-way ANOVA was used to examine sex and diagnosis interactions in ReHo and FC, followed by post-hoc analyses to explore FC biomarkers for different sexes.

Results

In ReHo analysis, the four groups showed significant sex and diagnosis interactions in the right middle frontal gyrus (rMFG). FC analysis with rMFG as the seed region revealed a significant sex and diagnosis interaction effect in FC of the rMFG with the bilateral postcentral gyrus (PoCG). In male IGD group, FC between the rMFG and the bilateral PoCG correlates strongly with daytime dysfunction score and the Pittsburgh sleep quality inventory (PSQI) total score.

Conclusion

These findings emphasize the importance of considering sexual dimorphism in the neurobiology of IGD, which might influence subsequent treatment strategies.

Consensus Paper: Cerebellum and Reward

Cerebellum is a key-structure for the modulation of motor, cognitive, social and affective functions, contributing to automatic behaviours through interactions with the cerebral cortex, basal ganglia and spinal cord. The predictive mechanisms used by the cerebellum cover not only sensorimotor functions but also reward-related tasks. Cerebellar circuits appear to encode temporal difference error and reward prediction error. From a chemical standpoint, cerebellar catecholamines modulate the rate of cerebellar-based cognitive learning, and mediate cerebellar contributions during complex behaviours. Reward processing and its associated emotions are tuned by the cerebellum which operates as a controller of adaptive homeostatic processes based on interoceptive and exteroceptive inputs. Lobules VI-VII/areas of the vermis are candidate regions for the cortico-subcortical signaling pathways associated with loss aversion and reward sensitivity, together with other nodes of the limbic circuitry. There is growing evidence that the cerebellum works as a hub of regional dysconnectivity across all mood states and that mental disorders involve the cerebellar circuitry, including mood and addiction disorders, and impaired eating behaviors where the cerebellum might be involved in longer time scales of prediction as compared to motor operations. Cerebellar patients exhibit aberrant social behaviour, showing aberrant impulsivity/compulsivity. The cerebellum is a master-piece of reward mechanisms, together with the striatum, ventral tegmental area (VTA) and prefrontal cortex (PFC). Critically, studies on reward processing reinforce our view that a fundamental role of the cerebellum is to construct internal models, perform predictions on the impact of future behaviour and compare what is predicted and what actually occurs.

Neuromarkers in addiction: definitions, development strategies, and recent advances

Substance use disorders (SUDs) are the most costly and prevalent psychiatric conditions. Recent calls emphasize a need for biomarkers-measurable, stable indicators of normal and abnormal processes and response to treatment or environmental agents-and, in particular, brain-based neuromarkers that will advance understanding of the neurobiological basis of SUDs and clinical practice. To develop neuromarkers, researchers must be grounded in evidence that a putative marker (i) is sensitive and specific to the psychological phenomenon of interest, (ii) constitutes a predictive model, and (iii) generalizes to novel observations (e.g., through internal cross-validation and external application to novel data). These neuromarkers may be used to index risk of developing SUDs (susceptibility), classify individuals with SUDs (diagnostic), assess risk for progression to more severe pathology (prognostic) or index current severity of pathology (monitoring), detect response to treatment (response), and predict individualized treatment outcomes (predictive). Here, we outline guidelines for developing and assessing neuromarkers, we then review recent advances toward neuromarkers in addiction neuroscience centering our discussion around neuromarkers of craving-a core feature of SUDs. In doing so, we specifically focus on the Neurobiological Craving Signature (NCS), which show great promise for meeting the demand of neuromarkers.

Parameter Space and Potential for Biomarker Development in 25 Years of fMRI Drug Cue Reactivity: A Systematic Review

Importance

In the last 25 years, functional magnetic resonance imaging drug cue reactivity (FDCR) studies have characterized some core aspects in the neurobiology of drug addiction. However, no FDCR-derived biomarkers have been approved for treatment development or clinical adoption. Traversing this translational gap requires a systematic assessment of the FDCR literature evidence, its heterogeneity, and an evaluation of possible clinical uses of FDCR-derived biomarkers.

Objective

To summarize the state of the field of FDCR, assess their potential for biomarker development, and outline a clear process for biomarker qualification to guide future research and validation efforts.

Evidence Review

The PubMed and Medline databases were searched for every original FDCR investigation published from database inception until December 2022. Collected data covered study design, participant characteristics, FDCR task design, and whether each study provided evidence that might potentially help develop susceptibility, diagnostic, response, prognostic, predictive, or severity biomarkers for 1 or more addictive disorders.

Findings

There were 415 FDCR studies published between 1998 and 2022. Most focused on nicotine (122 [29.6%]), alcohol (120 [29.2%]), or cocaine (46 [11.1%]), and most used visual cues (354 [85.3%]). Together, these studies recruited 19 311 participants, including 13 812 individuals with past or current substance use disorders. Most studies could potentially support biomarker development, including diagnostic (143 [32.7%]), treatment response (141 [32.3%]), severity (84 [19.2%]), prognostic (30 [6.9%]), predictive (25 [5.7%]), monitoring (12 [2.7%]), and susceptibility (2 [0.5%]) biomarkers. A total of 155 interventional studies used FDCR, mostly to investigate pharmacological (67 [43.2%]) or cognitive/behavioral (51 [32.9%]) interventions; 141 studies used FDCR as a response measure, of which 125 (88.7%) reported significant interventional FDCR alterations; and 25 studies used FDCR as an intervention outcome predictor, with 24 (96%) finding significant associations between FDCR markers and treatment outcomes.

Conclusions and Relevance

Based on this systematic review and the proposed biomarker development framework, there is a pathway for the development and regulatory qualification of FDCR-based biomarkers of addiction and recovery. Further validation could support the use of FDCR-derived measures, potentially accelerating treatment development and improving diagnostic, prognostic, and predictive clinical judgments.

A three-dimensional model of neural activity and phenomenal-behavioral patterns

How phenomenal experience and behavior are related to neural activity in physiology and psychopathology represents a fundamental question in neuroscience and psychiatry. The phenomenal-behavior patterns may be deconstructed into basic dimensions, i.e., psychomotricity, affectivity, and thought, which might have distinct neural correlates. This work provides a data overview on the relationship of these phenomenal-behavioral dimensions with brain activity across physiological and pathological conditions (including major depressive disorder, bipolar disorder, schizophrenia, attention-deficit/hyperactivity disorder, anxiety disorders, addictive disorders, Parkinson's disease, Tourette syndrome, Alzheimer's disease, and frontotemporal dementia). Accordingly, we propose a three-dimensional model of neural activity and phenomenal-behavioral patterns. In this model, neural activity is organized into distinct units in accordance with connectivity patterns and related input/output processing, manifesting in the different phenomenal-behavioral dimensions. (1) An external neural unit, which involves the sensorimotor circuit/brain's sensorimotor network and is connected with the external environment, processes external inputs/outputs, manifesting in the psychomotor dimension (processing of exteroception/somatomotor activity). External unit hyperactivity manifests in psychomotor excitation (hyperactivity/hyperkinesia/catatonia), while external unit hypoactivity manifests in psychomotor inhibition (retardation/hypokinesia/catatonia). (2) An internal neural unit, which involves the interoceptive-autonomic circuit/brain's salience network and is connected with the internal/body environment, processes internal inputs/outputs, manifesting in the affective dimension (processing of interoception/autonomic activity). Internal unit hyperactivity manifests in affective excitation (anxiety/dysphoria-euphoria/panic), while internal unit hypoactivity manifests in affective inhibition (anhedonia/apathy/depersonalization). (3) An associative neural unit, which involves the brain's associative areas/default-mode network and is connected with the external/internal units (but not with the environment), processes associative inputs/outputs, manifesting in the thought dimension (processing of ideas). Associative unit hyperactivity manifests in thought excitation (mind-wandering/repetitive thinking/psychosis), while associative unit hypoactivity manifests in thought inhibition (inattention/cognitive deficit/consciousness loss). Finally, these neural units interplay and dynamically combine into various neural states, resulting in the complex phenomenal experience and behavior across physiology and neuropsychiatric disorders.

The cerebellum plays more than one role in the dysregulation of appetite: Review of structural evidence from typical and eating disorder populations

OBJECTIVE

Dysregulated appetite control is characteristic of anorexia nervosa (AN), bulimia nervosa (BN), and obesity (OB). Studies using a broad range of methods suggest the cerebellum plays an important role in aspects of weight and appetite control, and is implicated in both AN and OB by reports of aberrant gray matter volume (GMV) compared to nonclinical populations. As functions of the cerebellum are anatomically segregated, specific localization of aberrant anatomy may indicate the mechanisms of its relationship with weight and appetite in different states. We sought to determine if there were consistencies in regions of cerebellar GMV changes in AN/BN and OB, as well as across normative (NOR) variation.

METHOD

Systematic review and meta-analysis using GingerALE.

RESULTS

Twenty-six publications were identified as either case-control studies (nOB  = 277; nAN/BN  = 510) or regressed weight from NOR data against brain volume (total n = 3830). AN/BN and OB analyses both showed consistently decreased GMV within Crus I and Lobule VI, but volume reduction was bilateral for AN/BN and unilateral for OB. Analysis of the NOR data set identified a cluster in right posterior lobe that overlapped with AN/BN cerebellar reduction. Sensitivity analyses indicated robust repeatability for NOR and AN/BN cohorts, but found OB-specific heterogeneity.

DISCUSSION

Findings suggest that more than one area of the cerebellum is involved in control of eating behavior and may be differentially affected in normal variation and pathological conditions. Specifically, we hypothesize an association with sensorimotor and emotional learning via Lobule VI in AN/BN, and executive function via Crus I in OB.

The role of the cerebellum in internet gaming disorder-A systematic review

Recent studies increasingly highlight involvement of the cerebellum in drug craving and addiction. However, its exact role, that is, whether the cerebellum is a critical component of a brain network underlying addictive behaviour, or whether it rather is a facilitator or mediator, is still unclear. Findings concerning the newly recognized internet gaming disorder (IGD) suggest that changes in cerebellar connectivity and functioning are associated with behavioural/non-substance addiction. Here, we systematically review the literature on IGD and cerebellar involvement following the PRISMA guidelines. A total of 13 neuroimaging studies met the inclusion criteria. Studies utilized a broad range of diagnostic instruments and resulting cut-off criteria, rendering it difficult to compare findings. Results on altered cerebro-cerebellar connectivity in patients with IGD are mixed; most studies report altered or increased functional connectivity. Moreover, decreased cerebellar grey matter volume is reported. Studies have further indicated that differential activation patterns in the cerebellum may enable discrimination between healthy subjects and subjects with IGD, even allowing for prediction of treatment outcomes. Given the strong connectivity between the cerebellum and cerebral regions, the cerebellum may act as an intermediary between regions involved in craving and addiction and consequently affect symptoms of IGD. Results suggest differential involvement of the cerebellar lobes, emphasizing a need for high-resolution parcellation of the cerebellum in future studies. However, the studies included in the present review have small sample sizes and include mostly male participants. Thus, results may have limited generalizability yet highlight a crucial role of the cerebellum in IGD that needs further investigation.

Metabolic profiles associated with opioid use and opioid use disorder: a narrative review of the literature

Purpose of Review

Opioid use disorder (OUD) is a chronic, relapsing condition that is epidemic in the USA. OUD is associated with serious adverse consequences, including higher incarceration rates, impaired medical and mental health, and overdose-related fatalities. Several medications with demonstrated clinical efficacy in reducing opioid use are approved to treat OUD. However, there is evidence that medications for OUD cause metabolic impairments, which raises concerns over the long-term metabolic health of individuals recovering from OUD. Here, we summarize the scientific literature on the metabolic effects of the use of opioids, including medications for treating OUD.

Recent Findings

Our findings showed lower body weight and adiposity, and better lipid profiles in individuals with OUD. In individuals with diabetes mellitus, opioid use was associated with lower blood glucose levels. In contrast, among individuals without underlying metabolic conditions, opioids promoted insulin resistance. Treatment of OUD patients with the agonists methadone or buprenorphine caused weight gain, increased liking and intake of sugar, and impaired lipid profile and glucose metabolism, whereas treatment with the antagonist naltrexone demonstrated evidence for reduced sweet preferences.

Summary

Our findings highlighted a gap in knowledge regarding the safety of medications for OUD. Further research is needed to determine how best to reduce the risk of metabolic disorder in the treatment of OUD with opioid agonists versus antagonists.

Appetitive and aversive cue reactivities differentiate neural subtypes of alcohol drinkers

Craving reflects the subjective urge to use drugs and can be triggered by both positive and negative emotional states. No studies have systematically investigated the relative roles of these mechanisms in the pathophysiology of substance misuse. Here, we performed meta-analyses of drug cue-elicited reactivity and win and loss processing in the monetary incentive delay task to identify distinct neural correlates of appetitive and aversive responses to drug cues. We then characterized the appetitive and aversive cue responses in seventy-six alcohol drinkers performing a cue craving task during fMRI. Imaging data were processed according to published routines. The appetitive circuit involved medial cortical regions and the ventral striatum, and the aversive circuit involved the insula, caudate and mid-cingulate cortex. We observed a significant correlation of cue-elicited activity (β estimates) of the appetitive and aversive circuit. However, individuals varied in appetitive and aversive cue responses. From the regression of appetitive (y) vs. aversive (x) β, we identified participants in the top 1/3 each of those with positive and negative residuals as "approach" (n = 15) and "avoidance" (n = 11) and the others as the "mixed" (n = 50) subtype. In clinical characteristics, the avoidance subtype showed higher sensitivity to punishment and, in contrast, the approach subtype showed higher levels of sensation seeking and alcohol expectancy for social and physical pressure. The findings highlighted distinct neural underpinnings of appetitive and aversive components of cue-elicited reactivity and provided evidence for potential subtypes of alcohol drinkers.

Highly processed foods can be considered addictive substances based on established scientific criteria

BACKGROUND

There is growing evidence that an addictive-eating phenotype may exist. There is significant debate regarding whether highly processed foods (HPFs; foods with refined carbohydrates and/or added fats) are addictive. The lack of scientifically grounded criteria to evaluate the addictive nature of HPFs has hindered the resolution of this debate.

ANALYSIS

The most recent scientific debate regarding a substance's addictive potential centered around tobacco. In 1988, the Surgeon General issued a report identifying tobacco products as addictive based on three primary scientific criteria: their ability to (1) cause highly controlled or compulsive use, (2) cause psychoactive (i.e. mood-altering) effects via their effect on the brain and (3) reinforce behavior. Scientific advances have now identified the ability of tobacco products to (4) trigger strong urges or craving as another important indicator of addictive potential. Here, we propose that these four criteria provide scientifically valid benchmarks that can be used to evaluate the addictiveness of HPFs. Then, we review the evidence regarding whether HPFs meet each criterion. Finally, we consider the implications of labeling HPFs as addictive.

CONCLUSION

Highly processed foods (HPFs) can meet the criteria to be labeled as addictive substances using the standards set for tobacco products. The addictive potential of HPFs may be a key factor contributing to the high public health costs associated with a food environment dominated by cheap, accessible and heavily marketed HPFs.

Addicted to green: priming effect of menthol cigarette packaging on brain response to smoking cues

INTRODUCTION

Mentholated tobacco cigarettes are believed to be more addictive than non-menthol ones. Packaging of most menthol cigarette brands includes distinctive green hues, which may act as conditioned stimuli (ie, cues) and promote menthol smoking. To examine the cue properties of menthol cigarette packaging, we used a priming paradigm to assess the effect of packaging on the neural substrates of smoking cue reactivity. We hypothesised that menthol packaging will exert a specific priming effect potentiating smoking cue reactivity in menthol compared with non-menthol smokers.

METHODS

Forty-two menthol and 33 non-menthol smokers underwent functional MRI while viewing smoking and neutral cues. The cues were preceded (ie, primed) by briefly presented images of menthol or non-menthol cigarette packages. Participants reported craving for cigarettes in response to each cue.

RESULTS

Menthol packaging induced greater frontostriatal and occipital smoking cue reactivity in menthol smokers than in non-menthol smokers. Menthol packaging also enhanced the mediation by neural activity of the relationship between cue exposure and cigarette craving in menthol but not non-menthol smokers. Dynamic causal modelling showed stronger frontostriatal-occipital connectivity in response to menthol packaging in menthol compared with non-menthol smokers. The effects of non-menthol packaging did not differ between categories of smokers.

CONCLUSIONS

Our findings demonstrate heightened motivational and perceptual salience of the green-hued menthol cigarette packaging that may exacerbate menthol smokers' susceptibility to smoking cues. These effects could contribute to the greater addiction severity among menthol smokers and could be considered in the development of science-based regulation and legal review of tobacco product marketing practices.

A neuromarker for drug and food craving distinguishes drug users from non-users

Craving is a core feature of substance use disorders. It is a strong predictor of substance use and relapse and is linked to overeating, gambling, and other maladaptive behaviors. Craving is measured via self-report, which is limited by introspective access and sociocultural contexts. Neurobiological markers of craving are both needed and lacking, and it remains unclear whether craving for drugs and food involve similar mechanisms. Across three functional magnetic resonance imaging studies (n = 99), we used machine learning to identify a cross-validated neuromarker that predicts self-reported intensity of cue-induced drug and food craving (P < 0.0002). This pattern, which we term the Neurobiological Craving Signature (NCS), includes ventromedial prefrontal and cingulate cortices, ventral striatum, temporal/parietal association areas, mediodorsal thalamus and cerebellum. Importantly, NCS responses to drug versus food cues discriminate drug users versus non-users with 82% accuracy. The NCS is also modulated by a self-regulation strategy. Transfer between separate neuromarkers for drug and food craving suggests shared neurobiological mechanisms. Future studies can assess the discriminant and convergent validity of the NCS and test whether it responds to clinical interventions and predicts long-term clinical outcomes.

The Dopamine System in Mediating Alcohol Effects in Humans

Brain-imaging studies show that the development and maintenance of alcohol use disorder (AUD) is determined by a complex interaction of different neurotransmitter systems and multiple psychological factors. In this context, the dopaminergic reinforcement system appears to be of fundamental importance. We focus on the excitatory and depressant effects of acute versus chronic alcohol intake and its impact on dopaminergic neurotransmission. Furthermore, we describe alterations in dopaminergic neurotransmission as associated with symptoms of alcohol dependence. We specifically focus on neuroadaptations to chronic alcohol consumption and their effect on central processing of alcohol-associated and reward-related stimuli. Altered reward processing, complex conditioning processes, impaired reinforcement learning, and increased salience attribution to alcohol-associated stimuli enable alcohol cues to drive alcohol seeking and consumption. Finally, we will discuss how the neurobiological and neurochemical mechanisms of alcohol-associated alterations in reward processing and learning can interact with stress, cognition, and emotion processing.

Disrupted functional connectivity of the brain reward system in substance use problems: A meta-analysis of functional neuroimaging studies

Extensive literature suggests that the brain reward system is crucial in understanding the neurobiology of substance use disorders. However, evidence of reliable deficits in functional connectivity across studies on substance use problems remains limited. Therefore, a voxel-wise seed-based meta-analysis using brain regions of the reward system as seeds of interest was conducted on 96 studies representing 5757 subjects with substance use problems. The ventromedial prefrontal cortex exhibited hyperconnectivity with the ventral striatum and hypoconnectivity with the amygdala and hippocampus. The executive striatum showed hyperconnectivity with the motor thalamus and dorsolateral prefrontal cortex and hypoconnectivity with the anterior cingulate cortex and anterior insula. Finally, the limbic striatum was found to be hyperconnected to the orbitofrontal cortex and hypoconnected to the precuneus compared with healthy subjects. The current study provided meta-analytical evidence of deficient functional connectivity between brain regions of the reward system and cortico-striato-thalamocortical loops in addiction. These results are consistent with deficits in motivation and habit formation occurring in addiction, and they highlight alterations in brain regions involved in socio-emotional processing and attention salience.

Neural Correlates of Cue Reactivity and the Regulation of Craving in Substance Use Disorders

Abstract. Theoretical background: Considerable progress has been made in illuminating the neural basis of the compulsive use patterns characterizing substance use disorders. It has been suggested to utilize these findings to alleviate the health burden associated with substance use. Objective: We address how neuroimaging research can provide these benefits. Methods: Based on neurobiological models of addiction, we highlight neuroimaging research elucidating neural predictors of relapse and how treatments modify these markers. Results: With the focus on cue reactivity, brain activity related to the motivational salience of drugs and automatized use behaviors can predict relapse. Cue reactivity changes with abstinence, and it remains to be determined whether such changes confer periods of critical relapse susceptibility. Conclusions: Several established and emerging interventions modulate brain activity associated with drug value. However, executive deficits in addiction may compromise interventions targeting control-related prefrontal brain areas. Lastly, it remains more difficult to change the brain responses mediating habitual behaviors.

Neural cue-reactivity in pathological gambling as evidence for behavioral addiction: a systematic review

Increasing incidence of problem gambling has led to prioritizing the problem from the point of view of public health. Additionally, gambling disorder has been recently classified as a behavioral addiction, with implications for both its diagnosis and treatment. However, the shared neural substrate of addictions, to substances and behavioral, is still discussed. Thus, this systematic review aims to provide up-to-date knowledge from the past five years (2017-2022) concerning the neural correlates of gambling related stimuli (cue-reactivity) on the basis of a previous review (Brevers et al., Cognitive, Affective and Behavioral Neuroscience 18:718-729, 2019). A total of five studies were included in the review. Activation of brain areas related to memory, reward and executive functions could be the underlying mechanism of this behavioral addiction. Specifically, nucleus accumbens and striatum (ventral and dorsal), parahippocampal regions, the right amygdala and several prefrontal cortex regions have systematically been found more active in those subjects exposed to gambling-related cues. Also, the insula could play a pivotal role connecting these three systems in a highly integrated neural network with several implications for reward processing modulation, associative learning and top-down attentional regulation to improve saliency of addiction-related cues. These results are consistent with previous findings on other substance addictions, such as alcohol, tobacco, marijuana or cocaine. The study of neural reactivity to stimuli related to addiction could be useful as a biomarker of the severity of the disorder, the efficacy of the treatment, the risk of relapse, in addition to being an objective criterion to measure the effectiveness of prevention campaigns.

The effects of prefrontal vs. parietal cortex transcranial direct current stimulation on craving, inhibition, and measures of self-esteem

While prefrontal cortex dysfunction has been implicated in high food cravings, other cortical regions, like the parietal cortex, are potentially also involved in regulating craving. This study explored the effects of stimulating the inferior parietal lobule (IPL) and dorsolateral prefrontal cortex (DLPFC) on food craving state and trait. Transcranial direct current stimulation (tDCS) was administered at 1.5 mA for 5 consecutive days. Participants received 20 min of IPL, DLPFC, or sham stimulation (SHAM) each day which consisted of two rounds of 10-min stimulation, divided by a 10-min mindfulness task break. In addition, we studied inhibition and subjective psychological aspects like body image and self-esteem state and trait. To decompose immediate and cumulative effects, we measured the following on days 1 and 5: inhibition through the Go/No-go task; and food craving, self-esteem, and body appreciation through a battery of questionnaires. We found that false alarm errors decreased in the participants receiving active stimulation in the DLPFC (DLPFC-group). In contrast, false alarm errors increased in participants receiving active stimulation in the IPL (IPL-group). At the same time, no change was found in the participants receiving SHAM (SHAM-group). There was a trending reduction in craving trait in all groups. Momentary craving was decreased in the DLPFC-group and increased in IPL-group, yet a statistical difference was not reached. According to time and baseline, self-esteem and body perception improved in the IPL-group. Furthermore, self-esteem trait significantly improved over time in the DLPFC-group and IPL-group. These preliminary results indicate that tDCS modulates inhibition in frontoparietal areas with opposite effects, enhancing it in DLPFC and impairing it in IPL. Moreover, craving is moderately linked to inhibition, self-esteem, and body appreciation which seem not to be affected by neuromodulation but may rely instead on broader regions as more complex constructs. Finally, the fractionated protocol can effectively influence inhibition with milder effects on other constructs.

From ensembles to meta-ensembles: Specific reward encoding by correlated network activity

Neuronal ensembles are local, sparsely distributed populations of neurons that are reliably re-activated by a specific stimulus, context or task. Such discrete cell populations can be defined either functionally, by electrophysiological recordings or in vivo calcium imaging, or anatomically, using the expression of markers such as the immediate early gene cFos. A typical example of tasks that involve the formation of neuronal ensembles is reward learning, such as the cue-reward pairing during operant conditioning. These ensembles are re-activated during cue-presentation and increasing evidence suggests that this re-activation is the neurophysiological basis for the execution of reward-seeking behavior. Whilst the pursuit of rewards is a common daily activity, it is also related to the consumption of drugs, such as alcohol, and may result in problematic behaviors including addiction. Recent research has identified neuronal ensembles in several reward-related brain regions that control distinct aspects of a conditioned response, e.g., contextual information about the availability of a specific reward or the actions needed to retrieve this reward under the given circumstances. Here, we review studies using the activity marker cFos to identify and characterize neuronal ensembles related to alcohol and non-drug rewards with a special emphasis on the discrimination between different rewards by meta-ensembles, i.e., by dynamic co-activation of multiple ensembles across different brain areas.

Effects of pharmacological and genetic regulation of COMT activity in alcohol use disorder: a randomized, placebo-controlled trial of tolcapone

Alcohol Use Disorder (AUD) is characterized by loss of control over drinking. Behavioral control is mediated, in part, by cortical dopamine signaling. Inhibition of catechol-O-methyltransferase (COMT), the enzyme primarily responsible for cortical dopamine inactivation, may increase cortical dopamine, especially among individuals with genetically mediated lower dopaminergic tone, such as COMT rs4680 (val158met) val-allele homozygotes. This study was a randomized, placebo-controlled, pharmacogenetic trial of the COMT inhibitor tolcapone. Ninety non-treatment-seeking AUD individuals were prospectively genotyped for rs4680 and randomized to tolcapone (200 mg t.i.d.) or placebo for 8 days. At baseline and on day 7, peripheral COMT activity was assayed, and participants completed an fMRI alcohol cue-reactivity task; on day 8, they completed a bar-lab paradigm. Primary outcomes were: (1) natural drinking during the medication period; (2) alcohol self-administration in the bar lab; and (3) alcohol cue-elicited cortical (right inferior frontal gyrus [rIFG]) and ventral striatal activation. At baseline, the rs4680 val-allele had an additive effect on COMT activity. Tolcapone, relative to placebo, reduced COMT activity in all genotype groups. COMT genotype moderated tolcapone's effect on drinking during the medication period and in the bar lab, such that tolcapone, relative to placebo, reduced drinking only among val-allele homozygotes. Tolcapone did not affect cue-elicited ventral striatal activation but reduced rIFG activation; less rIFG activation on day 7 was associated with less drinking during the medication period. Taken together, these data suggest that COMT inhibition may reduce drinking specifically among individuals genetically predisposed to excessive COMT activity and potentially low cortical dopamine tone.ClinicalTrials.gov identifier: NCT02949934 https://clinicaltrials.gov/ct2/show/NCT02949934.

Prefrontal cortical response to natural rewards and self-reported anhedonia are associated with greater craving among recently withdrawn patients in residential treatment for opioid use disorder

Both anhedonia and craving are common among patients with opioid use disorder (OUD), and are associated with vulnerability to relapse. Although these constructs are theoretically linked relatively few studies have examined them together. In the current study, recently withdrawn patients (N = 71) in residential treatment for prescription OUD underwent a cue reactivity paradigm while being monitored with functional near-infrared spectroscopy (fNIRS). Patients also self-reported symptoms of anhedonia via the Snaith-Hamilton Pleasure Scale (SHAPS), while smartphone-based ecological momentary assessments (EMA) were used to measure craving levels. On average, lower right prefrontal cortex (PFC) activity in response to positive social stimuli was associated with higher craving (β = - 2.87; S.E. = 1.23; p = 0.02). Self-reported anhedonia moderated the association between PFC activity and craving (β = - 1.02; S.E. = 0.48; p = 0.04), such that patients with two or more anhedonic symptoms had a significant and stronger negative association between PFC activation to hedonically positive images and craving, compared to patients with fewer than two anhedonic symptoms, among whom the association was not significant. This finding provides evidence that higher levels of anhedonia among patients in residential treatment for OUD are associated with a stronger link between lower PFC response to positive social experiences and higher levels of craving, potentially increasing overall vulnerability to relapse.

Aberrant intrinsic neural network strength in individuals with "smartphone addiction": An MRI data fusion study

BACKGROUND AND OBJECTIVES

Excessive smartphone use, also referred to as "smartphone addiction" (SPA), has increasingly attracted neuroscientific interest due to its similarities with other behavioral addictions, particularly internet gaming disorder. Little is known about the neural mechanisms underlying smartphone addiction. We explored interrelationships between brain structure and function to specify neurobiological correlates of SPA on a neural system level.

METHODS

Gray matter volume (GMV) and intrinsic neural activity (INA) were investigated in individuals with SPA (n = 20) and controls (n = 24), using multimodal magnetic resonance imaging and multivariate data fusion techniques, that is, parallel independent component analysis.

RESULTS

The joint analysis of both data modalities explored shared information between GMV and INA. In particular, two amplitudes of low frequency fluctuations-based independent neural systems significantly differed between individuals with SPA and controls. A medial/dorsolateral prefrontal system exhibited lower functional network strength in individuals with SPA versus controls, whereas the opposite pattern was detected in a parietal cortical/cerebellar system. Neural network strength was significantly related to duration of smartphone use and sleep difficulties.

DISCUSSION AND CONCLUSIONS

We show modality-specific associations of the brain's resting-state activity with distinct and shared SPA symptom dimensions. In particular, the data suggest contributions of aberrant prefrontal and parietal neural network strength as a possible signature of deficient executive control in SPA.

SCIENTIFIC SIGNIFICANCE

This study suggests distinct neural mechanisms underlying specific biological and behavioral dimensions of excessive smartphone use.

Late positive potential as a candidate biomarker of motivational relevance in substance use: Evidence from a meta-analysis

The objective of the current meta-analysis was to assess the effect size of the Late Positive Potential (LPP) to drug and emotional cues in substance users compared to controls. The secondary objective was to test for moderation by: age, gender, years of use, use status, and substance type. Search was performed in August 2021 using PubMed. Inclusion criteria were: substance use disorder/dependence or validated self-report, LPP means, healthy control comparison, non-acute drug study, data available, peer-reviewed journal, English, and human participants. Selection bias was tested through modified Egger's regression and exploratory 3-parameter selection model tests. Results (k = 11) indicated LPP to drug cues was larger in substance use compared to control group, with a large effect size (Hedges' g=1.66, 95%CI [0.64,2.67], p = 0.005). There were no overall differences for emotional cues. Though threats of selection bias were not severe, inclusion of more studies with larger sample sizes in future meta-analyses will allow more robust tests of publication bias and more accurate measures of effect size.

The effects of Transcranial Direct Current Stimulation on food craving and food intake in individuals affected by obesity and overweight: a mini review of the magnitude of the effects

Obesity represents one of the wellness diseases concurring to increase the incidence of diabetes, cardiovascular diseases, and cancer. One of the main perpetuating factors of obesity is food craving, which is characterized by an urgent desire to eat a large and various amount of food, regardless of calories requirement or satiety signals, and it might be addressed to the alteration of the dorsolateral prefrontal cortex (DLPFC) activity. Despite most of the gold-standard therapies focus on symptom treatment only, non-invasive brain stimulation techniques such as transcranial direct current stimulation (tDCS) could help treat overeating by modulating specific neural pathways. The current systematic review was conducted to identify whether convergent evidence supporting the usefulness of tDCS to deal with food craving are present in the literature. The review was conducted by searching articles published up to January 1^st 2022 on MEDLINE, Scopus and PsycInfo databases. We included studies investigating the effects of tDCS on food craving in subjects affected by overweight and obesity. According to eligibility criteria, 5 articles were included. Results showed that tDCS targeting left DLPFC with unipolar montage induced ameliorating effects on food craving. Controversial results were shown for the other studies, that might be ascribable to the use of bipolar montage, and the choice of other target areas. Further investigations including expectancy effect control, larger sample sizes and follow-up are needed to support more robust conclusions. To conclude, tDCS combined with the use of psychoeducative intervention, diet and physical activity, might represents a potential to manage food craving in individuals with overweight and obesity.

Is addiction a brain disease? A plea for agnosticism and heterogeneity

RATIONALE

Although increasingly subject to criticism, the brain disease model of addiction (BDMA) remains dominant within addiction science. Yet few advocates or critics of the BDMA have provided an account of what a brain disease is. The aim of this review is to conceptually clarify what it would mean for the BDMA to be true, rather than to argue decisively for or against it.

OBJECTIVES

Conceptual clarification of the BDMA requires consideration of possible models of disease and their relationship to the BDMA. A barrier to such consideration is belief that the BDMA is necessary to combatting addiction stigma. To address this barrier, I begin with discussion of what we know about the effects of the brain disease label on addiction stigma, and why labelling effects should have no bearing on the validity of the BDMA. I then distinguish strong, minimal, network, and mismatch models of disease, and I argue that the BDMA aligns with a strong disease model. This means that underlying brain pathology is hypothesized to be the cause of the personal-level observable signs and experienced symptoms characteristic of addiction. Evaluation of the BDMA therefore requires analysis of the concepts of brain dysfunction and causation, and their application to addiction science.

RESULTS

Brain dysfunction cannot be analyzed merely as brain changes or brain differences; nor can it be inferred merely from the presence of personal-level signs and symptoms. It is necessary to have an account of normal brain function by which to measure it. The theoretical and empirical challenges to developing such an account are not insurmountable, but they are substantial. Although there exist competing analyses of causation, there is a relatively standard method used to establish it within experimental science: intervention. Using this method, the causal significance of brain states, such as, e.g., extensive gray matter loss and/or neuroadapations in the mesocorticolimbic dopamine system, is not yet fully demonstrated. Further studies are necessary to determine their effect compared with other possible variables, such as, e.g., alternative reinforcers.

CONCLUSIONS

Conceptual clarification and preliminary empirical assessment of the BDMA recommends agnosticism about its validity and an openness to heterogeneity; in some cases addiction may be a brain disease, in others not. Either way, addiction stigma can be combatted by fighting moralism about drugs and moralistic drug policies directly, as opposed to resting hopes on the brain disease label.

Cortical surface variation in individuals with excessive smartphone use

Excessive smartphone use has been repeatedly related to adverse effects on mental health and psychological well-being in young adults. The continued investigation of the neurobiological mechanism underlying excessive smartphone use - sometimes also referred to as "smartphone addiction" (SPA) - is considered a top priority in system neuroscience research. Despite progress in the past years, cortical morphology associated with SPA is still poorly understood. Here, we used structural magnetic resonance imaging (MRI) at 3 T to investigate two cortical surface markers of distinct neurodevelopmental origin such as the complexity of cortical folding (CCF) and cortical thickness (CTh) in individuals with excessive smartphone use (n = 19) compared to individuals not fulfilling SPA criteria (n-SPA; n = 22). SPA was assessed using the Smartphone Addiction Inventory (SPAI). CCF and CTh were investigated using the Computational Anatomy Toolbox (CAT12). SPA individuals showed lower CCF in the right superior frontal gyrus as well as in the right caudal (cACC) and rostral anterior cingulate cortex (rACC) compared to n-SPA individuals (TFCE, uncorrected at p < 0.001). Following a dimensional approach, across the entire sample CCF of the right cACC was significantly associated with SPAI total score, as well as with distinct SPAI subdimensions, particularly time spent with the device, compulsivity, and sleep interference in all participants (n = 41; p < 0.05, FDR-corrected). Collectively, these findings suggest that SPA is associated with aberrant structural maturation of regions important for cognitive control and emotional regulation. This article is protected by copyright. All rights reserved.

Personalized treatment - which interaction ingredients should be focused to capture the unconscious

A recent meta-analysis revealed that mental health and baseline psychological impairment affect the quality of life and outcomes in different chronic conditions. Implementing mental health care in physical care services is still insufficient. Thus, interdisciplinary communication across treatment providers is essential. The standardized language provided by the diagnostic statistical manual favors a clear conceptualization. However, this approach might not focus on the individual, as thinking in categories might impede recognizing the continuum from healthy to diseased. Psychoanalytic theory is concerned with an individual’s unconscious conflictual wishes and motivations, manifested through enactments like psychic symptoms or (maladaptive) behavior with long-term consequences if not considered. Such modifiable internal and external factors often are inadequately treated. However, together with the physical chronic condition constraints, these factors determine degrees of freedom for a self-determined existence. The effect of therapeutic interventions, and especially therapy adherence, relies on a solid therapeutic relationship. Outcome and process research still investigates the mechanism of change in psychotherapeutic treatments with psychanalysis’s focus on attachment problems. This article examines existing knowledge about the mechanism of change in psychoanalysis under the consideration of current trends emerging from psychotherapy research. A clinical example is discussed. Additionally, further directions for research are given. The theoretical frame in psychoanalytic therapies is the affect-cognitive interface. Subliminal affect-perception is enabled via awareness of subjective meanings in oneself and the other; shaping this awareness is the main intervention point. The interactional ingredients, the patient’s inherent bioenvironmental history meeting the clinician, are relevant variables. Several intrinsic, subliminal parameters relevant for changing behavior are observed. Therapeutic interventions aim at supporting the internalization of the superego’s functions and at making this ability available in moments of self-reflection. By supporting mentalization abilities, a better understanding of oneself and higher self-regulation (including emotional regulation) can lead to better judgments (application of formal logic and abstract thinking). Thus, this facilitates enduring behavior change with presumably positive effects on mental and physical health.

Temporally dynamic neural correlates of drug cue reactivity, response inhibition, and methamphetamine-related response inhibition in people with methamphetamine use disorder

Cue-induced drug craving and disinhibition are two essential components of continued drug use and relapse in substance use disorders. While these phenomena develop and interact across time, the temporal dynamics of their underlying neural activity remain under-investigated. To explore these dynamics, an analysis of time-varying activation was applied to fMRI data from 62 men with methamphetamine use disorder in their first weeks of recovery in an abstinence-based treatment program. Using a mixed block-event, factorial cue-reactivity/Go-NoGo task and a sliding window across the task duration, dynamically-activated regions were identified in three linear mixed effects models (LMEs). Habituation to drug cues across time was observed in the superior temporal gyri, amygdalae, left hippocampus, and right precuneus, while response inhibition was associated with the sensitization of temporally-dynamic activations across many regions of the inhibitory frontoparietal network. Methamphetamine-related response inhibition was associated with temporally-dynamic activity in the parahippocampal gyri and right precuneus (corrected p-value < 0.001), which show a declining cue-reactivity contrast and an increasing response inhibition contrast. Overall, the declining craving-related activations (habituation) and increasing inhibition-associated activations (sensitization) during the task duration suggest the gradual recruitment of response inhibitory processes and a concurrent habituation to drug cues in areas with temporally-dynamic methamphetamine-related response inhibition. Furthermore, temporally dynamic cue-reactivity and response inhibition were correlated with behavioral and clinical measures such as the severity of methamphetamine use and craving, impulsivity and inhibitory task performance. This exploratory study demonstrates the time-variance of the neural activations undergirding cue-reactivity, response inhibition, and response inhibition during exposure to drug cues, and suggests a method to assess this dynamic interplay. Analyses that can capture temporal fluctuations in the neural substrates of drug cue-reactivity and response inhibition may prove useful for biomarker development by revealing the rate and pattern of sensitization and habituation processes, and may inform mixed cue-exposure intervention paradigms which could promote habituation to drug cues and sensitization in inhibitory control regions.

Similarities and differences between internet gaming disorder and tobacco use disorder: A large-scale network study

Studies have shown that internet gaming disorder (IGD) has the potential to be a type of addiction; however, direct comparisons (similarities and differences) between IGD and traditional addictions remain scarce, especially at the neuroimaging level. Resting-state functional magnetic resonance imaging (fMRI) data were collected from 92 individuals with IGD, 96 individuals with tobacco use disorders (TUDs) and 107 individuals who served as healthy controls (HCs). Independent component analysis (ICA) was performed to explore the similarities and differences among these three groups; Granger causality analysis (GCA) was further performed based on the ICA results to determine potential neural features underlying the differences and similarities among the groups. The ICA results indicated significant differences in the subcortical network and cerebellar network. GCA results found that significant differences in bilateral caudate among three groups, and the efferents of dorsal frontostriatal circuit showed significant differences in insula among three groups, whereas efferents of ventral frontostriatal circuit showed significant differences in the medial prefrontal cortex (mPFC). Two kinds of addiction showed differences in thalamus and frontostriatal circuits, and similar changes found in cerebellum and mPFC regions. It suggested that addiction disorders have psychopathology features, and the craving and reward dysfunctions may be the key reasons. Although both substance addiction and behaviour addiction showed craving dysfunction in cerebellum, however, the key reward dysfunction of substance addiction was found in subcortical regions, whereas behaviour addiction located in cortical regions.

From a systems view to spotting a hidden island: A narrative review implicating insula function in alcoholism

Excessive use of alcohol promotes the development of alcohol addiction, but the understanding of how alcohol-induced brain alterations lead to addiction remains limited. To further this understanding, we adopted an unbiased discovery strategy based on the principles of systems medicine. We used functional magnetic resonance imaging data from patients and animal models of alcohol addiction-like behaviors, and developed mathematical models of the 'relapse-prone' network states to identify brain sites and functional networks that can be selectively targeted by therapeutic interventions. Our systems level, non-local, and largely unbiased analyses converged on a few well-defined brain regions, with the insula emerging as one of the most consistent finding across studies. In proof-of-concept experiments we were able to demonstrate that it is possible to guide network dynamics towards increased resilience in animals but an initial translation into a clinical trial targeting the insula failed. Here, in a narrative review, we summarize the key experiments, methodological developments and knowledge gained from this completed round of a discovery cycle moving from identification of 'relapse-prone' network states in humans and animals to target validation and intervention trial. Future concerted efforts are necessary to gain a deeper understanding of insula function a in a state-dependent, circuit-specific and cell population perspective, and to develop the means for insula-directed interventions, before therapeutic targeting of this structure may become possible.

Altered Global Signal Topography in Alcohol Use Disorders

The most common symptom of patients with alcohol use disorders (AUD) is cognitive impairment that negatively affects abstinence. Presently, there is a lack of indicators for early diagnosis of alcohol-related cognitive impairment (ARCI). We aimed to assess the cognitive deficits in AUD patients with the help of a specific imaging marker for ARCI. Data-driven dynamic and static global signal topography (GST) methods were applied to explore the cross-talks between local and global neuronal activities in the AUD brain. Twenty-six ARCI, 54 AUD without cognitive impairment (AUD-NCI), and gender/age-matched 40 healthy control (HC) subjects were recruited for this study. We found that there was no significant difference with respect to voxel-based morphometry (VBM) and static GST between AUD-NCI and ARCI groups. And in dynamic GST measurements, the AUD-NCI patients had the highest coefficient of variation (CV) at the right insula, followed by ARCI and the HC subjects. In precuneus, the order was reversed. There was no significant correlation between the dynamic GST and behavioral scores or alcohol consumption. These results suggested that dynamic GST might have potential implications in understanding AUD pathogenesis and disease management.

Test-retest reliability of neural alcohol cue-reactivity: Is there light at the end of the magnetic resonance imaging tube?

Over the last decades, the assessment of alcohol cue-reactivity gained popularity in addiction research, and efforts were undertaken to establish neural biomarkers. This attempt however depends on the reliability of cue-induced brain activation. Thus, we assessed test-retest reliability of alcohol cue-reactivity and its implications for imaging studies in addiction. We investigated test-retest reliability of alcohol cue-induced brain activation in 144 alcohol-dependent patients over 2 weeks. We computed established reliability estimates, such as intraclass correlation (ICC), Dice and Jaccard coefficients, for the three contrast conditions of interest: 'alcohol', 'neutral' and the 'alcohol versus neutral' difference contrast. We also investigated how test-retest reliability of the different contrasts affected the capacity to establishing associations with clinical data and determining effect size estimates. Whereas brain activation, indexed by the constituting contrast conditions 'alcohol' and 'neutral' separately, displayed overall moderate (ICC > 0.4) to good (ICC > 0.75) test-retest reliability in areas of the mesocorticolimbic system, the difference contrast 'alcohol versus neutral' showed poor overall reliability (ICC < 0.40), which was related to the intercorrelation between the constituting conditions. Data simulations and analyses of craving data confirmed that the low reliability of the difference contrast substantially limited the capacity to establish associations with clinical data and precisely estimate effect sizes. Future research on alcohol cue-reactivity should be cautioned by the low reliability of the common 'alcohol versus neutral' difference contrast. We propose that this limitation can be overcome by using the constituent task conditions as an individual difference measure, when intending to longitudinally monitor brain responses.

Abnormal functional connectivity of the anterior cingulate cortex subregions mediates the association between anhedonia and sleep quality in major depressive disorder

BACKGROUND

The anterior cingulate cortex (ACC) is a crucial region in the pathophysiology of major depressive disorder (MDD). However, the relationship between functional alterations of the ACC subregions, anhedonia and sleep quality remains unclear in MDD patients.

METHODS

The resting-state functional connectivity (rsFC) of ACC subregions was measured in 41 first-episode medication-naïve MDD patients and 63 healthy controls who underwent functional magnetic resonance imaging. Between-group differences were examined using two-sample t-test. Furthermore, correlation and mediation analyses were carried out to investigate the relationships between the aberrant rsFC of ACC subregions, anhedonia and sleep quality in the patients and controls.

RESULTS

Compared to healthy controls, the MDD patients exhibited increased rsFC of ACC subregions to areas of the anterior default mode network (DMN) and showed decreased rsFC of the right subgenual ACC to left precuneus (PCUN), which belongs to the posterior DMN. In MDD group, the sleep quality and consummatory anhedonia are correlated with some rsFC, which involves the angular gyrus (ANG) and superior frontal gyrus (SFG). More importantly, the rsFC between the right perigenual ACC and left SPG mediates the association between anhedonia and sleep quality in MDD.

LIMITATIONS

The cross-sectional design and the subjective questionaries for assessment.

CONCLUSION

These findings confirm the functional alterations of the ACC subregions and reveal the mediating role of ACC subregions in sleep and reward dysfunction in MDD.

Psilocybin targets a common molecular mechanism for cognitive impairment and increased craving in alcoholism

Alcohol-dependent patients commonly show impairments in executive functions that facilitate craving and can lead to relapse. However, the molecular mechanisms leading to executive dysfunction in alcoholism are poorly understood, and new effective pharmacological treatments are desired. Here, using a bidirectional neuromodulation approach, we demonstrate a causal link between reduced prefrontal mGluR2 function and both impaired executive control and alcohol craving. A neuron-specific prefrontal mGluR2 knockdown in rats generated a phenotype of reduced cognitive flexibility and excessive alcohol seeking. Conversely, virally restoring prefrontal mGluR2 levels in alcohol-dependent rats rescued these pathological behaviors. In the search for a pharmacological intervention with high translational potential, psilocybin was capable of restoring mGluR2 expression and reducing relapse behavior. Last, we propose a FDG-PET biomarker strategy to identify mGluR2 treatment-responsive individuals. In conclusion, we identified a common molecular pathological mechanism for both executive dysfunction and alcohol craving and provided a personalized mGluR2 mechanism-based intervention strategy for medication development for alcoholism.

The cue-reactivity paradigm: An ensemble of networks driving attention and cognition when viewing drug and natural reward-related stimuli

The cue-reactivity paradigm is a widely adopted neuroimaging probe engendering brain activity linked with attentional, affective, and reward processes following presentation of appetitive stimuli. Given the multiple mental operations invoked, we sought to decompose cue-related brain activity into constituent components employing emergent meta-analytic techniques when considering drug and natural reward-related cues. We conducted coordinate-based meta-analyses delineating common and distinct brain activity convergence across cue-reactivity studies (N = 196 articles) involving drug (n = 133) or natural (n = 63) visual stimuli. Across all studies, convergence was observed in limbic, cingulate, insula, and fronto-parieto-occipital regions. Drug-distinct convergence was observed in posterior cingulate, dorsolateral prefrontal, and temporo-parietal regions, whereas distinct-natural convergence was observed in thalamic, insular, orbitofrontal, and occipital regions. We characterized connectivity profiles of identified regions by leveraging task-independent and task-dependent MRI datasets, grouped these profiles into subnetworks, and linked each with putative mental operations. Outcomes suggest multifaceted brain activity during cue-reactivity can be decomposed into elemental processes and indicate that while drugs of abuse usurp the brain's natural-reward-processing system, some regions appear distinct to drug cue-reactivity.

Multivariate pattern analysis links drug use severity to distributed cortical hypoactivity during emotional inhibitory control in opioid use disorder

Opioid use disorder (OUD) is characterized by emotional and cognitive impairements that are associated with poor treatment outcomes. The present study investigated the neural mechanism underlying emotion evaluation and inhibitory control using an affective go/no-go (AGN) task and its association with drug use severity and craving in patients with OUD. Twenty-six recently detoxified patients with OUD underwent functional magnetic resonance imaging (fMRI) while performing the AGN task that required response to frequently presented appetitive stimuli ("go") and inhibition of response to infrequently presented aversive stimuli ("no-go"). The fMRI session was immediately followed by an injection of extended-release opioid antagonist naltrexone (XR-NTX). Participants' opioid craving was assessed immediately before fMRI and 10 ± 2 days after XR-NTX injection. Multivariate pattern analysis (MVPA) showed that drug use severity was associated with distributed brain hypoactivity in response to aversive no-go stimuli, with particularly large negative contributions from the cognitive control and dorsal attention brain networks. While drug use severity and its associated MVPA brain response pattern were both correlated with opioid craving at baseline, only the brain response pattern predicted craving during XR-NTX treatment. Our findings point to widespread functional hypoactivity in the brain networks underlying emotional inhibitory control in OUD. Such a distributed pattern is consistent with the multifaceted nature of OUD, which affects multiple brain networks. It also highlights the utility of the multivariate approach in uncovering large-scale cortical substrates associated with clinical severity in complex psychiatric disorders and in predicting treatment response.

Adverse social experiences in adolescent rats result in persistent sex-dependent effects on alcohol-seeking behavior

BACKGROUND

Accumulating clinical evidence suggests that women with prior exposure to adverse childhood experiences are more susceptible to heavy drinking and other health-related behaviors. Yet, preclinical studies investigating sex-dependent effects of adolescent adverse social experiences (ASEs) on later alcohol-seeking behavior are lacking. This is mainly due to the unavailability of valid animal models and a shortage of studies that compare effects in males and females. Therefore, we sought to investigate the sex-dependent effects of ASE on adult alcohol-seeking behavior, locomotion, and reward sensitivity in male and female rats.

METHODS

We recently developed a rat model for childhood/adolescent peer rejection that allows us to study the long-term consequences of ASEs. Adolescent Wistar rats were reared from postnatal day (pd) 21 to pd 50 either within a group of Fischer 344 rats (ASE) or within a group of Wistar rats (control). Wistar rats housed with Fischer 344 rats do not reciprocate social play in adolescence. This reduced play across adolescence mimics peer rejection and results in chronic dysregulation of social and pain-related behaviors. We tested adult male and female rats in the reinstatement paradigm for cue-induced alcohol-seeking behavior, circadian locomotor activity, and sucrose consumption long after the termination of the peer rejection condition.

RESULTS

Peer rejection induced persistent sex-dependent changes in alcohol cue-induced reinstatement. Females showed an increased reinstatement effect while peer-rejected males demonstrated a decrease. Sex differences were observed in locomotor activity or reward sensitivity to sucrose.

CONCLUSIONS

Peer rejection has long-lasting sex-dependent consequences on alcohol-seeking behavior without affecting locomotion or sweet reward sensitivity. Our results suggest that peer-rejected female rats represent a vulnerable population in which to study relapse-like behaviors that are similar to clinical findings, while males seem to buffer the peer rejection effect and demonstrate resilience to later life alcohol-seeking behaviors, as measured by the reinstatement effect. Finally, we provide a novel approach to investigate the molecular and neurobiological underpinnings of ASEs on alcohol and other drug-seeking behaviors.

Neural mechanisms of sexual decision-making in women with alcohol use disorder

RATIONALE

The co-occurrence of alcohol consumption and sexual activity is associated with increased risk for sexual assault, sexually transmitted disease, and unplanned pregnancy among young adult women with alcohol use disorder (AUD). There is considerable previous work demonstrating neural reactivity to alcohol cues in AUD. Because alcohol consumption and sexual behavior are both rewarding and tend to co-occur, sexual cues may produce similar neural reactivity in women with AUD, possibly indicating a shared mechanism underlying reactivity to both types of cues. Alternatively, reactivity to alcohol versus sexual cues may be distinct, suggesting domain-specific mechanisms.

OBJECTIVES

We investigated whether the decision vulnerabilities in AUD women regarding sexual activity were related to differences in brain activation compared to control women.

METHODS

Women with (n = 15) and without (n = 16) AUD completed a hypothetical decision-making task during fMRI that presented low- or high-risk scenarios involving visual sexual, appetitive, and neutral cues.

RESULTS

Results showed that sexual cues were more often endorsed by women with AUD compared to controls and elicited differential brain activation patterns in frontal, visual, and reward regions. During high-risk decisions, women with AUD failed to downregulate activation, causing hyperactivation compared to controls.

CONCLUSIONS

Visual sexual cues produced reactivity like that previously demonstrated for alcohol cues, suggesting a shared or domain-general mechanism for alcohol and sexual cue reactivity in women with AUD. Riskier sexual decisions in women with AUD may be a consequence of repeatedly pairing alcohol use and sexual activity, a characteristic behavior of this population.

Links between problem gambling and spending on booster packs in collectible card games: A conceptual replication of research on loot boxes

Loot boxes are digital containers of randomised rewards present in some video games which are often purchasable for real world money. Recently, concerns have been raised that loot boxes might approximate traditional gambling activities, and that people with gambling problems have been shown to spend more on loot boxes than peers without gambling problems. Some argue that the regulation of loot boxes as gambling-like mechanics is inappropriate because similar activities which also bear striking similarities to traditional forms of gambling, such as collectable card games, are not subject to such regulations. Players of collectible card games often buy sealed physical packs of cards, and these 'booster packs' share many formal similarities with loot boxes. However, not everything which appears similar to gambling requires regulation. Here, in a large sample of collectible card game players (n = 726), we show no statistically significant link between in real-world store spending on physical booster and problem gambling (p = 0.110, η2 = 0.004), and a trivial in magnitude relationship between spending on booster packs in online stores and problem gambling (p = 0.035, η2 = 0.008). Follow-up equivalence tests using the TOST procedure rejected the hypothesis that either of these effects was of practical importance (η2 > 0.04). Thus, although collectable card game booster packs, like loot boxes, share structural similarities with gambling, it appears that they may not be linked to problem gambling in the same way as loot boxes. We discuss potential reasons for these differences. Decisions regarding regulation of activities which share structural features with traditional forms of gambling should be made on the basis of definitional criteria as well as whether people with gambling problems purchase such items at a higher rate than peers with no gambling problems. Our research suggests that there is currently little evidence to support the regulation of collectable card games.

Functional evaluation of NK1 antagonism on cue reactivity in opiate dependence; An fMRI study

BACKGROUND

Opiate addiction is a major health challenge with substantial societal cost. Though harm minimisation strategies have been effective, there is a growing need for new treatments for detoxification and relapse prevention. Preclinical research has found neurokinin 1 (NK1) receptors have prominent effects on opiate reward and reinforcement, and human studies have found NK1 antagonism led to reductions in craving and withdrawal. However, its effect on brain mechanisms in opiate addiction has not yet been examined.

METHODS

This study aims to assess the impact of NK1 antagonist aprepitant on heroin cue-elicited changes in blood-oxygenation level dependent (BOLD) signal in opiate dependent individuals undergoing detoxification. Participants will attend two scanning sessions and receive a single dose of aprepitant (320 mg) and a placebo in a randomised, cross-over design. During functional magnetic resonance imaging participants will undergo two runs of a cue reactivity task, which consists of passive viewing of drug cues or neutral cues in a block design fashion. We hypothesise that NK1 antagonism will attenuate the BOLD response to drug cues in the caudate nucleus and amygdala. Regions of interest were selected based on NK1 receptor density and their role in cue reactivity and craving.

Predictors of weight loss in participants with obesity following bariatric surgery - A prospective longitudinal fMRI study

Prevalence rates of overweight and obesity are increasing worldwide and are amongst the leading causes of death. Participants with obesity also suffer from poorer mental health with a concomitant reduced quality of life. Bariatric surgery outperforms other existing weight optimization approaches. However, hitherto, it was not possible to identify factors predicting weight loss following surgery. Therefore, we aimed at investigating neural and behavioral predictors of weight loss, as well as the neurological underpinnings of food cue-induced craving before and after bariatric surgery. The total sample consisted of 26 participants with obesity (17 females and 9 males, mean age 41 ± 12 years, mean BMI 46 ± 6 kg/m2, 21 received Roux-en-Y gastric bypass and 5 sleeve gastrectomy). Participants with obesity were prospectively assessed using functional magnetic resonance imaging two weeks before, as well as eight and 24 weeks after surgery. Imaging data were available for 11 individuals; 10 received Roux-en-Y gastric bypass and one sleeve gastrectomy. Subjective cue-induced food craving correlated positively with brain activation in the amygdala, the parahippocampal gyrus, and hippocampus, and negatively with brain activation in frontal brain regions. In the total sample (N = 26), perceived feeling of hunger and YFAS sum score explained 50.6% of the variance (R² = 0.506, F_(1,23) = 10.759, p < 0.001) and in the imaging sample, cue-induced food craving at baseline before surgery explained 49.6% of the variance (R² = 0.496, F_(1,23) = 7.862, p = 0.023) of % total weight loss (%TWL). In other words, with respect to %TWL, bariatric surgery was most efficient in candidates characterized by high cue-induced food craving, high-perceived feeling of hunger and a low YFAS sum score.

Sensory cue reactivity: Sensitization in alcohol use disorder and obesity

Neuroimaging techniques to measure the function of the human brain such as electroencephalography (EEG), positron emission tomography (PET), and functional magnetic resonance imaging (fMRI), are powerful tools for understanding the underlying neural circuitry associated with alcohol use disorder (AUD) and obesity. The sensory (visual, taste and smell) paradigms used in neuroimaging studies represent an ideal platform to investigate the connection between the different neural circuits subserving the reward/executive control systems in these disorders, which may offer a translational mechanism for novel intervention predictions. Thus, the current review provides an integrated summary of the recent neuroimaging studies that have applied cue-reactivity paradigms and neuromodulation strategies to explore underlying alterations in neural circuitry as well in treatment strategies in AUD and obesity. Finally, we discuss literature on mechanisms associated with increased alcohol sensitivity post-bariatric surgery (BS) which offers guidance for future research to use sensory percepts in elucidating the relation of reward signaling in AUD development post-BS.

Alcohol and sweet reward are encoded by distinct meta-ensembles

Cue-reward associations form distinct memories that can drive appetitive behaviors and cravings for both drugs and natural rewards. It is still unclear how such memories are encoded in the brain's reward system. We trained rats to concurrently self-administer either alcohol or a sweet saccharin solution as drug or natural rewards, respectively. Memory recall due to cue exposure reactivated reward-associated functional ensembles in reward-related brain regions, marked by a neural cFos response. While the local ensembles activated by cue presentation for either reward consisted of similar numbers of neurons, using advanced statistical network theory, we found robust reward-specific co-activation patterns across brain regions. Interestingly, the resulting meta-ensemble networks differed by the most influential regions, which in case of saccharin comprised the prefrontal cortex, while for alcohol seeking control shifted to insular cortex with strong involvement of the amygdala. Our results support the view of memory representation as a differential co-activation of local neuronal ensembles. This article is part of the special issue on 'Neurocircuitry Modulating Drug and Alcohol Abuse'.

The imbalance between goal-directed and habitual systems in internet gaming disorder: Results from the disturbed thalamocortical communications

BACKGROUND

Converging evidence has identified the imbalance between goal-directed systems and habitual systems in the addiction process. The thalamocortical loop plays an important role in the habitual/goal-directed system. However, little is known about the role of the thalamus in goal-directed and habitual systems in Internet gaming disorder (IGD) patients. This study investigated whether thalamocortical circuit was disrupted and how they affected goal-directed and habitual behaviors in IGD patients.

METHODS

This is a functional magnetic resonance imaging (fMRI) study. Twenty-five IGD patients and 25 matched recreational game users (RGUs) were scanned when they were in a resting state and were performing an instrumental learning task to obtain behavioral data related to habitual/goal-directed behavior. We used the whole-brain seed-based functional connectivity (FC) of the four thalamic nuclei (bilateral) and correlation analyses to examine the thalamocortical loop difference and relationship with habitual/goal-directed performance.

RESULTS

Compared with RGUs, IGD patients demonstrated significantly increased FC between the left midline nucleus (MN) and the right postcentral gyrus (PCG), and between the pulvinar and medial frontal gyrus (MFG). Correlation results showed that within the IGD group, the correct response rates of the participants to inconsistent stimulus-result pairs were positively correlated with the FC between the pulvinar and MFG. Inhibition-control scores were negatively correlated with the FC between the left MN and the PCG.

CONCLUSIONS

IGD patients showed disrupted thalamocortical communication that could further result in an imbalance between the goal-directed and habitual systems in IGD patients. These findings provide more information about the involvement of the thalamus in the pathophysiology of IGD, and as potential circuit-level biomarkers of IGD patients, these circuit alterations may be useful in treatment development and in monitoring treatment outcomes.

BDNF influences neural cue-reactivity to food stimuli and food craving in obesity

There is increasing evidence that brain-derived neurotrophic factor (BDNF) impacts on the development of obesity. We are the first to test the hypothesis that BDNF levels might be associated with neural reactivity to food cues in patients suffering from obesity and healthy controls. We assessed visual food cue-induced neural response in 19 obese patients and 20 matched controls using functional magnetic resonance imaging and analyzed the associations between BDNF levels, food cue-reactivity and food craving. Whole-brain analysis in both groups revealed that food cues elicited higher neural activation in clusters of mesolimbic brain areas including the insula (food > neutral). Patients suffering from obesity showed a significant positive correlation between plasma BDNF levels and visual food cue-reactivity in the bilateral insulae. In addition, patients suffering from obesity with positive food cue-induced insula activation also reported significantly higher food craving than those with low cue-reactivity-an effect that was absent in normal weight participants. The present findings implicate that BDNF levels in patients suffering from obesity might be involved in food craving and obesity in humans. This highlights the importance to consider BDNF pathways when investigating obesity and obesity treatment.

Patterns of brain function associated with cannabis cue-reactivity in regular cannabis users: a systematic review of fMRI studies

RATIONALE

Regular cannabis use (i.e. ≥ monthly) is highly prevalent, with past year use being reported by ~ 200 million people globally.High reactivity to cannabis cues is a key feature of regular cannabis use and has been ascribed to greater cannabis exposure and craving, but the underlying neurobiology is yet to be systematically integrated.

OBJECTIVES

We aim to systematically summarise the findings from fMRI studies which examined brain function in cannabis users while exposed to cannabis vs neutral stimuli during a cue-reactivity fMRI task.

METHODS

A systematic search of PsycINFO, PubMed and Scopus databases was pre-registered in PROSPERO (CRD42020171750) and conducted following PRISMA guidelines. Eighteen studies met inclusion/exclusion criteria. Samples comprised 918 participants (340 female) aged 16-38 years. Of these, 603 were regular cannabis users, and 315 were controls.

RESULTS

The literature consistently reported greater brain activity in cannabis users while exposed to cannabis vs neutral stimuli in three key brain areas: the striatum, the prefrontal (anterior cingulate, middle frontal) and the parietal cortex (posterior cingulate/precuneus) and additional brain regions (hippocampus, amygdala, thalamus, occipital cortex). Preliminary correlations emerged between cannabis craving and the function of partially overlapping regions (amygdala, striatum, orbitofrontal cortex ).

CONCLUSIONS

Exposure to cannabis-cues may elicit greater brain function and thus trigger cravings in regular cannabis users and thus trigger cannabis craving. Standardised and longitudinal assessments of cannabis use and related problems are required to profile with greater precision the neurobiology of cannabis cue-reactivity, and its role in predicting  cravings and relapse.

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.