Neural activity related to drug craving in cocaine addiction

Possible association of elevated CSF IL-6 levels with anxiety and frustration in psychiatric disorders

AIM

Neuroinflammation is an important causal factor for a variety of psychiatric disorders. We previously reported increased cerebrospinal fluid interleukin-6 levels in patients with schizophrenia and major depressive disorder. The present study aimed to examine the possible association of interleukin-6 levels with anxiety and frustration, negative valence symptoms shared in various psychiatric disorders.

METHODS

We included 129 patients with psychiatric disorders and 70 controls. CSF and plasma interleukin-6 levels were measured by immunoassay kits, and psychological symptoms were assessed with the State-Trait Anxiety Inventory, and the Basic Psychological Need Satisfaction and Frustration Scale. To examine regional cerebral blood flow, patients underwent arterial spin labeling analysis using magnetic resonance imaging.

RESULTS

Cerebrospinal fluid interleukin-6 levels were significantly correlated with State-Trait Anxiety Inventory-trait anxiety (r = 0.25, P = 0.046) and Basic Psychological Need Satisfaction and Frustration Scale-autonomy frustration scores (r = 0.29, P = 0.018). Patients with abnormally high cerebrospinal fluid interleukin-6 levels (defined >97.5 percentile of the controls) had higher scores for trait anxiety (P = 0.035) and autonomy frustration (P = 0.026), and significantly increased regional cerebral blood flow in the left superior temporal gyrus, bilateral nucleus accumbens, and cerebellum than the remaining patients.

CONCLUSION

Patients with elevated cerebrospinal fluid interleukin-6 constitute a subpopulation of psychiatric disorders associated with anxiety and autonomy frustration, which may be related to altered functions in specific brain areas.

Memory Reconsolidation Updating in Substance Addiction: Applications, Mechanisms, and Future Prospects for Clinical Therapeutics

Persistent and maladaptive drug-related memories represent a key component in drug addiction. Converging evidence from both preclinical and clinical studies has demonstrated the potential efficacy of the memory reconsolidation updating procedure (MRUP), a non-pharmacological strategy intertwining two distinct memory processes: reconsolidation and extinction-alternatively termed "the memory retrieval-extinction procedure". This procedure presents a promising approach to attenuate, if not erase, entrenched drug memories and prevent relapse. The present review delineates the applications, molecular underpinnings, and operational boundaries of MRUP in the context of various forms of substance dependence. Furthermore, we critically examine the methodological limitations of MRUP, postulating potential refinement to optimize its therapeutic efficacy. In addition, we also look at the potential integration of MRUP and neurostimulation treatments in the domain of substance addiction. Overall, existing studies underscore the significant potential of MRUP, suggesting that interventions predicated on it could herald a promising avenue to enhance clinical outcomes in substance addiction therapy.

Modulating reward and aversion: Insights into addiction from the paraventricular nucleus

BACKGROUND

Drug addiction, characterized by compulsive drug use and high relapse rates, arises from complex interactions between reward and aversion systems in the brain. The paraventricular nucleus (PVN), located in the anterior hypothalamus, serves as a neuroendocrine center and is a key component of the hypothalamic-pituitary-adrenal axis.

OBJECTIVE

This review aimed to explore how the PVN impacts reward and aversion in drug addiction through stress responses and emotional regulation and to evaluate the potential of PVN as a therapeutic target for drug addiction.

METHODS

We review the current literature, focusing on three main neuron types in the PVN-corticotropin-releasing factor, oxytocin, and arginine vasopressin neurons-as well as other related neurons, to understand their roles in modulating addiction.

RESULTS

Existing studies highlight the PVN as a key mediator in addiction, playing a dual role in reward and aversion systems. These findings are crucial for understanding addiction mechanisms and developing targeted therapies.

CONCLUSION

The role of PVN in stress response and emotional regulation suggests its potential as a therapeutic target in drug addiction, offering new insights for addiction treatment.

Connecting self-report and instrumental behavior during incubation of food craving in humans

Incubation of craving is a phenomenon describing the intensification of craving for a reward over extended periods of abstinence from reinforcement. Animal models use instrumental markers of craving to reward cues to examine incubation, while human paradigms rely on subjective self-reports. Here, we characterize an animal-inspired, novel human paradigm that showed strong positive relationships between self-reports and instrumental markers of craving for favored palatable foods. Further, we found consistent nonlinear relationships with time since last consumption and self-reports, and preliminary patterns between time and instrumental responses. These findings provide a novel approach to establishing an animal-inspired human model of incubation.

Reduced executive and reward connectivity is associated with smoking cessation response to repetitive transcranial magnetic stimulation: A double-blind, randomized, sham-controlled trial

Repetitive transcranial magnetic stimulation (rTMS) can reduce cue-elicited craving, decrease cigarette consumption, and increase the abstinence rate in tobacco use disorders (TUDs). We used functional magnetic resonance imaging (fMRI) to investigate the effect of 10 sessions of rTMS on cortical activity and neural networks in treatment-seeking smokers. Smoking cue exposure fMRI scans were acquired before and after the 10 sessions of active or sham rTMS (10 Hz, 3000 pulses per session) to the left dorsal lateral prefrontal cortex (DLPFC) in 42 treatment-seeking smokers (≥ 10 cigarettes per day). Brain activity and functional connectivity were compared before and after 10 sessions of rTMS. Ten sessions of rTMS significantly reduced the number of cigarettes consumed per day (62.93%) compared to sham treatment (39.43%) at the end of treatment (p = 0.027). fMRI results showed that the rTMS treatment increased brain activity in the dorsal anterior cingulate cortex (dACC) and DLPFC, but decreased brain activity in the bilateral medial orbitofrontal cortex (mOFC). The lower strength of dACC and mOFC connectivity was associated with quitting smoking (Wald score = 5.00, p = 0.025). The reduction of cigarette consumption significantly correlated with the increased brain activation in the dACC (r = 0.76, p = 0.0001). By increasing the brain activity in the dACC and prefrontal cortex and decreasing brain activity in the mOFC, 10 sessions of rTMS significantly reduced cigarette consumption and increased quit rate. Reduced drive-reward and executive control functional connectivity was associated with the smoking cessation effect from rTMS. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02401672.

Mesocorticolimbic function in cocaine polydrug users: A multimodal study of drug cue reactivity and cognitive regulation

Addictions are thought to be fostered by the emergence of poorly regulated mesocorticolimbic responses to drug-related cues. The development and persistence of these responses might be promoted by altered glutamate transmission, including changes to type 5 metabotropic glutamate receptors (mGluR5s). Unknown, however, is when these changes arise and whether the mGluR5 and mesocorticolimbic alterations are related. To investigate, non-dependent cocaine polydrug users and cocaine-naïve healthy controls underwent a positron emission tomography scan (15 cocaine users and 14 healthy controls) with [11 C]ABP688, and a functional magnetic resonance imaging scan (15/group) while watching videos depicting activities with and without cocaine use. For some drug videos, participants were instructed to use a cognitive strategy to lower craving. Both groups exhibited drug cue-induced mesocorticolimbic activations and these were larger in the cocaine polydrug users than healthy controls during the session's second half. During the cognitive regulation trials, the cocaine users' corticostriatal responses were reduced. [11 C]ABP688 binding was unaltered in cocaine users, relative to healthy controls, but post hoc analyses found reductions in those with 75 or more lifetime cocaine use sessions. Finally, among cocaine users (n = 12), individual differences in prefrontal [11 C]ABP688 binding were associated with midbrain and limbic region activations during the regulation trials. Together, these preliminary findings raise the possibility that (i) recreational polydrug cocaine users show biased brain processes towards cocaine-related cues and (ii) repeated cocaine use can lower cortical mGluR5 levels, diminishing the ability to regulate drug cue responses. These alterations might promote susceptibility to addiction and identify early intervention targets.

Physical Exercise to Redynamize Interoception in Substance use Disorders

Physical exercise is considered a promising medication-free and cost-effective adjunct treatment for substance use disorders (SUD). Nevertheless, evidence regarding the effectiveness of these interventions is currently limited, thereby signaling the need to better understand the mechanisms underlying their impact on SUD, in order to reframe and optimize them. Here we advance that physical exercise could be re-conceptualized as an "interoception booster", namely as a way to help people with SUD to better decode and interpret bodily-related signals associated with transient states of homeostatic imbalances that usually trigger consumption. We first discuss how mismatches between current and desired bodily states influence the formation of reward-seeking states in SUD, in light of the insular cortex brain networks. Next, we detail effort perception during physical exercise and discuss how it can be used as a relevant framework for re-dynamizing interoception in SUD. We conclude by providing perspectives and methodological considerations for applying the proposed approach to mixed-design neurocognitive research on SUD.

A thematic analysis of stress, substance-cue, and neutral/relaxing events to inform approaches for improving treatment among Black adults who use substances

INTRODUCTION

To inform approaches for adapting substance use treatment for Black adults, the aim of this study was to thematically analyze the stressors, triggers for substance use, and neutral/relaxing events reported among Black adults who participated in a lab paradigm.

METHODS

The sample included 36 Black adults (mean age [years] = 37.47, SD = 7.30; 53 % male, 12 (33 %) with alcohol use disorder, 12 (33 %) with cocaine use disorder, and 12 (33 %) healthy controls). All participants provided detailed stimulus and response context information on the most stressful event they experienced in the past year, an event that involved substance use, and a neutral/relaxing event in a structured interview using a scene development questionnaire, and this information was utilized to generate a personalized imagery script for each event using standardized procedures. Thematic analyses identified the key themes reported within scripts.

RESULTS

Consistent with a prior thematic analysis on a majority White sample, we found the following themes for the stress scripts: Relational (Violation, Loss, Parenting, Betrayal, Isolation vs. support), Environmental (Housing, Legal), and Achievement (Employment, Role in household). However, our analyses also resulted in new stress themes: Relational (Violation-Racial Microaggressions) and Institutional (Time Wasted). The substance use scripts consisted of the following trigger themes: Social (Social Facilitation, Socially-Sanctioned Substance Use Event, Exposure to Substance Use Friends/Associates), Internal (Free Time, Boredom, Thoughts of Using Substance, Frustration, Reward), and Environment (Availability of Substance, Celebration, Party Environment, Food, Hot Day, Money/Payday). The neutral/relaxing scripts themes were: Outdoor Activities (Admiring Nature, People Watching, Observing Surroundings, Enjoying the Sun, Playing in the Sand, Walking), Quiet Activities (Silence/Quiet, Prayer, Reading), and Indoor Activities (Radio, Television, Bath/Shower, Bed/Chair, Observing from a Window). We found sex differences across scripts.

CONCLUSIONS

The results suggest that Black people experience unique stressors (e.g., institutional and racial stressors) that are important to consider when modifying treatment to improve outcomes among this group. In addition to stressors, this study also identified high-risk situations involving triggers for use. Taken together these findings suggest targets for the tailoring of coping strategies that could be incorporated for the development of culturally relevant behavioral treatment for SUD.

Single-nucleus genomics in outbred rats with divergent cocaine addiction-like behaviors reveals changes in amygdala GABAergic inhibition

The amygdala processes positive and negative valence and contributes to addiction, but the cell-type-specific gene regulatory programs involved are unknown. We generated an atlas of single-nucleus gene expression and chromatin accessibility in the amygdala of outbred rats with high and low cocaine addiction-like behaviors following prolonged abstinence. Differentially expressed genes between the high and low groups were enriched for energy metabolism across cell types. Rats with high addiction index (AI) showed increased relapse-like behaviors and GABAergic transmission in the amygdala. Both phenotypes were reversed by pharmacological inhibition of the glyoxalase 1 enzyme, which metabolizes methylglyoxal-a GABAA receptor agonist produced by glycolysis. Differences in chromatin accessibility between high and low AI rats implicated pioneer transcription factors in the basic helix-loop-helix, FOX, SOX and activator protein 1 families. We observed opposite regulation of chromatin accessibility across many cell types. Most notably, excitatory neurons had greater accessibility in high AI rats and inhibitory neurons had greater accessibility in low AI rats.

ADX106772, an mGlu2 receptor positive allosteric modulator, selectively attenuates oxycodone taking and seeking

Opioid abuse and overdose have risen to epidemic proportions in the United States. Oxycodone is the most abused prescription opioid. Treatments for opioid use disorder (OUD) seek to reduce vulnerability to relapse by reducing sources of reinforcement to seek drug (i.e., acute drug effects or drug withdrawal/craving). Accumulating evidence that glutamate release elicits drug-seeking behaviors has generated interest in pharmacotherapies targeting the glutamate system. Agonists and positive allosteric modulators of the metabotropic glutamate 2 (mGlu2) receptor decrease glutamate activity, reducing drug taking and seeking. The present study tested whether the mGlu2 receptor positive allosteric modulator ADX106772 reduces oxycodone self-administration and the conditioned reinstatement of oxycodone seeking without affecting behaviors directed toward a highly palatable nondrug reinforcer (sweetened condensed milk). Male Wistar rats were trained to self-administer oxycodone (0.15 mg/kg/infusion, i.v., 12 h/day) or sweetened condensed milk (SCM; diluted 2:1 v/v in H2O, orally, 30 min/day) for 13 days in the presence of a contextual/discriminative stimulus (SD), and the ability of ADX106772 (0, 0.3, 1, 3 and-10 mg/kg, s. c.) to decrease self-administration was tested. The rats then underwent extinction training, during which oxycodone, SCM, and the SD were withheld. After extinction, the ability of ADX106772 to prevent SD-induced conditioned reinstatement of oxycodone and SCM seeking was tested. ADX106772 reduced oxycodone self-administration and conditioned reinstatement without affecting SCM self-administration or conditioned reinstatement. ADX106772 reduced oxycodone taking and seeking and did not affect the motivation for the palatable conventional reinforcer, SCM, suggesting that activating mGlu2 receptors with a positive allosteric modulator is a potential approach for prescription OUD treatment.

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.

Right inferior frontal gyrus theta-burst stimulation reduces smoking behaviors and strengthens fronto-striatal-limbic resting-state functional connectivity: a randomized crossover trial

Introduction

Functional and anatomical irregularities in the right inferior frontal gyrus (rIFG), a ventrolateral prefrontal region that mediates top-down inhibitory control over prepotent behavioral responding, are implicated in the ongoing maintenance of nicotine dependence (ND). However, there is little research on the effects of neuromodulation of the rIFG on smoking behavior, inhibitory control, and resting-state functional connectivity (rsFC) among individuals with ND.

Methods

In this double-blind, crossover, theta-burst stimulation (TBS) study, adults with ND (N = 31; female: n = 15) completed a baseline session and were then randomized to two counterbalanced sessions of functionally neuronavigated TBS to the rIFG: continuous TBS (cTBS) on 1 day and intermittent TBS (iTBS) on another. Differences in cigarette cravings, smoking, and fronto-striatal-limbic rsFC were assessed.

Results

Relative to baseline, cTBS significantly reduced appetitive and withdrawal cravings immediately after treatment. The effects of cTBS on withdrawal craving persisted for 24 h, as well as produced a reduction in smoking. Furthermore, cTBS significantly strengthened rsFC between the rIFG pars opercularis and subcallosal cingulate (fronto-striatal circuit), and between the rIFG pars opercularis and the right posterior parahippocampal gyrus (fronto-limbic circuit). At post-24 h, cTBS-induced increase in fronto-striatal rsFC was significantly associated with less appetitive craving, while the increase in fronto-limbic rsFC was significantly associated with less withdrawal craving and smoking.

Discussion

These findings warrant further investigation into the potential value of rIFG cTBS to attenuate smoking behavior among individuals with ND.

Neuroplastic Changes in Addiction Memory-How Music Therapy and Music-Based Intervention May Reduce Craving: A Narrative Review

Recent findings indicate that Music Therapy (MT) and Music-Based Interventions (MBIs) may reduce craving symptoms in people with Substance Use Disorders (SUD). However, MT/MBIs can lead SUD clients to recall memories associated with their drug history and the corresponding strong emotions (addiction memories). Craving is a central component of SUD, possibly linked to relapse and triggered by several factors such as the recall of memories associated with the drug experience. Therefore, to address the topic of what elements can account for an improvement in craving symptoms after MT/MBIs, we conducted a narrative review that (1) describes the brain correlates of emotionally salient autobiographical memories evoked by music, (2) outlines neuroimaging and neurophysiological studies suggesting how the experience of craving may encompass the recall of emotionally filled moments, and (3) points out the role of perineuronal nets (PNNs) in addiction memory neuroplasticity. We highlight how autobiographical memory retrieval, music-evoked autobiographical memories, and craving share similar neural activations with PNNs which represent a causal element in the processing of addiction memory. We finally conclude by considering how the neuroplastic characteristics of addiction memory might represent the ground to update and/or recalibrate, within the therapy, the emotional content related to the recall.

Pharmacological Treatments for Cocaine Craving: What Is the Way Forward? A Systematic Review

BACKGROUND

cocaine craving is a core feature of cocaine use disorder and remains a critical challenge for abstinence and relapse prevention. This review summarizes the anti-craving efficacy of pharmacotherapies tested for cocaine use disorder, in the context of randomized-controlled clinical trials.

OBJECTIVES

we assessed the databases of the U.S. National Library of Medicine, Google Scholar, and PsycINFO, without date restrictions up to August 2022, to identify relevant studies.

STUDY ELIGIBILITY CRITERIA, PARTICIPANTS, AND INTERVENTIONS

we included double-blinded randomized-controlled trials investigating pharmacotherapies for cocaine craving and/or cocaine use disorder whose outcomes included cocaine craving.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two authors screened studies' titles and abstracts for inclusion, and both read all the included studies. We systematically gathered information on the following aspects of each study: title; author(s); year of publication; sample size; mean age; sample characteristics; study set-ting; whether participants were treatment-seeking; study design; craving measures; study interventions; drop-out rates; and other relevant outcomes.

RESULTS

Overall, we appraised 130 clinical trials, including 8137 participants. We further considered the drugs from the studies that scored equal to or greater than six points in the quality assessment. There was a correlation between craving and cocaine use outcomes (self-reports, timeline follow-back or urinary benzoylecgonine) in the vast majority of studies. In the short-term treatment, acute phenylalanine-tyrosine depletion, clonidine, fenfluramine, meta-chlorophenylpiperazine (m-CPP) and mecamylamine presented promising effects. In the long term, amphetamine, biperiden, carbamazepine, lisdexamfetamine, lorcaserin, methamphetamine, mirtazapine, pioglitazone, progesterone, guanfacine, levodopa, nefazodone presented promising anti-craving effects. Unfortunately, the highly tested medications were not successful in most of the trials, as follows: propranolol in the short term; amantadine, aripiprazole, bromocriptine, citicoline, ketamine, modafinil, olanzapine, topiramate in the long term. The remaining 52 medications had no positive anti-craving outcomes.

LIMITATIONS

Our review was limited by high heterogeneity of craving assessments across the studies and by a great range of pharmacotherapies. Further, the majority of the studies considered abstinence and retention in treatment as the main outcomes, whereas craving was a secondary outcome and some of the studies evaluated patients with cocaine use disorder with comorbidities such as opioid or alcohol use disorder, schizophrenia, bipolar disorder or attention deficit hyperactivity. Lastly, most of the studies also included non-pharmacological treatments, such as counseling or psychotherapy.

CONCLUSIONS

There is a direct association between craving and cocaine use, underscoring craving as an important treatment target for promoting abstinence among persons with cocaine use disorder. Clonidine, fenfluramine and m-CPP showed to be promising medications for cocaine craving in the short-term treatment, and amphetamine, biperiden, carbamazepine, lisdexamfetamine, lorcaserin, methamphetamine, mirtazapine, pioglitazone, progesterone, guanfacine, levodopa, nefazodone in the long-term treatment.

Cerebellar Contributions to the Basal Ganglia Influence Motor Coordination, Reward Processing, and Movement Vigor

Both the cerebellum and the basal ganglia are known for their roles in motor control and motivated behavior. These two systems have been classically considered as independent structures that coordinate their contributions to behavior via separate cortico-thalamic loops. However, recent evidence demonstrates the presence of a rich set of direct connections between these two regions. Although there is strong evidence for connections in both directions, for brevity we limit our discussion to the better-characterized connections from the cerebellum to the basal ganglia. We review two sets of such connections: disynaptic projections through the thalamus and direct monosynaptic projections to the midbrain dopaminergic nuclei, the VTA and the SNc. In each case, we review the evidence for these pathways from anatomic tracing and physiological recordings, and discuss their potential functional roles. We present evidence that the disynaptic pathway through the thalamus is involved in motor coordination, and that its dysfunction contributes to motor deficits, such as dystonia. We then discuss how cerebellar projections to the VTA and SNc influence dopamine release in the respective targets of these nuclei: the NAc and the dorsal striatum. We argue that the cerebellar projections to the VTA may play a role in reward-based learning and therefore contribute to addictive behavior, whereas the projection to the SNc may contribute to movement vigor. Finally, we speculate how these projections may explain many of the observations that indicate a role for the cerebellum in mental disorders, such as schizophrenia.

Learning from addiction: Craving of prescription opioids in chronic pain sufferers

Prescription opioids are a primary driver of opioid-related deaths. Although craving is a substantial component of OUD, the degree to which craving leads to misuse among chronic pain patients on long-term prescription opioids is unknown. A clear understanding of the factors that lead to misuse in this vulnerable population is needed for the development of safe and effective practices for opioid taper. This narrative review summarizes the relevant literature on the role of craving in addiction and chronic pain through epidemiological and behavioral studies. The first part of this review examines the role of craving in predicting opioid use/misuse in individuals with chronic pain with and without OUD. The second part covers methods on how craving is evaluated experimentally using both subjective and objective measures and provides related findings. The overall goal of this review is to facilitate the development of a population-specific description of craving in those who use opioids to control chronic pain and to describe how it may be mechanistically linked to patterns of opioid (mis)use.

A motivation model of sex addiction - Relevance to the controversy over the concept

An integrative model of sexual addiction is presented, involving a combination of models based upon (i) incentive motivation theory and (ii) the dual organisation of the control of behavior. The model is related to ongoing arguments about the validity of the notion of addiction when applied to sexual behavior. It is suggested that the evidence strongly favors the viability of an addiction model of sex. Strong similarities to the classical addiction to hard drugs are observed and features can be better understood with the help of the model. These include tolerance, escalation and withdrawal symptoms. It is argued that other candidates for accounting for the phenomena, such as obsessive-compulsive behavior, faulty impulse control, high drive and hypersexuality do not fit the evidence. The role of dopamine is central to the model. The model's relevance to stress, abuse, development, psychopathy, fantasy, sex differences, evolutionary psychology and the interaction with drug-taking is shown.

Practical Considerations for Treating Comorbid Posttraumatic Stress Disorder in the Addictions Clinic: Approaches to Clinical Care, Leadership, and Alleviating Shame

A practical, common-sense framework for recognizing and addressing comorbid posttraumatic stress disorder (PTSD) in the substance use disorder (SUD) clinic is outlined. The article focuses on strategies that can help establish trauma-informed care or augment an existing approach. Interventions are organized around the task of ameliorating shame (or shame sensitivity), which represents a transdiagnostic mediator of psychopathology and, potentially, capacity for change. Countershaming strategies can guide a trauma-responsive leadership approach. Considering the striking rate of underdiagnosis of PTSD among patients with SUD, implementing routine systematic PTSD screening likely represents the single most consequential trauma-informed intervention that SUD clinics can adopt.

Disrupting reconsolidation by PKA inhibitor in BLA reduces heroin-seeking behavior

Drug abuse is considered a maladaptive pathology of emotional memory and is associated with craving and relapse induced by drug-associated stimuli or drugs. Reconsolidation is an independent memory process with a strict time window followed by the reactivation of drug-associated stimulus depending on the basolateral amygdala (BLA). Pharmacology or behavior treatment that disrupts the reconsolidation can effectively attenuate drug-seeking in addicts. Here, we hypothesized that heroin-memory reconsolidation requires cAMP-dependent protein kinase A (PKA) of BLA based on the fundamental effect of PKA in synaptic plasticity and memory process. After 10 days of acquisition, the rats underwent 11 days of extinction training and then received the intra-BLA infusions of the PKA inhibitor Rp-cAMPS at different time windows with/without a reactivation session. The results show that PKA inhibitor treatment in the reconsolidation time window disrupts the reconsolidation and consequently reduces cue-induced reinstatement, heroin-induced reinstatement, and spontaneous recovery of heroin-seeking behavior in the rats. In contrast, there was no effect on cue-induced reinstatement in the intra-BLA infusion of PKA inhibitor 6 h after reactivation or without reactivation. These data suggest that PKA inhibition disrupts the reconsolidation of heroin-associated memory, reduces subsequent drug seeking, and prevents relapse, which is retrieval-dependent, time-limited, and BLA-dependent.

Are There Neural Overlaps of Reactivity to Illegal Drugs, Tobacco, and Alcohol Cues? With Evidence From ALE and CMA

Abuses of most illegal drugs, including methamphetamine, marijuana, cocaine, heroin, and polydrug, are usually in conjunction with alcohol and tobacco. There are similarities and associations between the behavior, gene, and neurophysiology of such abusers, but the neural overlaps of their cue-reactivity and the correlation of neural overlap with drug craving still needs to be further explored. In this study, an Activation Likelihood Estimation (ALE) was performed on brain activation under legal (tobacco, alcohol) and illegal drug cues, for identifying the similarities in brain functions between different craving states. A Comprehensive meta-analysis (CMA) on the correlation coefficient between brain activation and craving scores in the selected literatures with subjective craving reports explained the degree of the craving via brain imaging results. In ALE, co-activation areas of the three cue-reactivity (posterior cingulate, caudate, and thalamus) suggest that the three cue-reactivity may all arouse drug-use identity which is a predictor of relapse and generation of conditioned reflexes under reward memory, thus leading to illegal drug relapses. In CMA, the brain activation was significantly correlated with subjective craving, with a correlation coefficient of 0.222. The neural overlap of tobacco, alcohol and most of the prevalent illegal drug cues not only further helps us understand the neural mechanism of substance co-abuse and relapse, but also provides implications to detoxification. Furthermore, the correlation between brain activation and craving is low, suggesting the accuracy of craving-based quantitative evaluation by neuroimaging remains unclear.

Sex Differences in Opioid and Psychostimulant Craving and Relapse: A Critical Review

A widely held dogma in the preclinical addiction field is that females are more vulnerable than males to drug craving and relapse. Here, we first review clinical studies on sex differences in psychostimulant and opioid craving and relapse. Next, we review preclinical studies on sex differences in psychostimulant and opioid reinstatement of drug seeking after extinction of drug self-administration, and incubation of drug craving (time-dependent increase in drug seeking during abstinence). We also discuss ovarian hormones' role in relapse and craving in humans and animal models and speculate on brain mechanisms underlying their role in cocaine craving and relapse in rodent models. Finally, we discuss imaging studies on brain responses to cocaine cues and stress in men and women.The results of the clinical studies reviewed do not appear to support the notion that women are more vulnerable to psychostimulant and opioid craving and relapse. However, this conclusion is tentative because most of the studies reviewed were correlational, not sufficiently powered, and not a priori designed to detect sex differences. Additionally, imaging studies suggest sex differences in brain responses to cocaine cues and stress. The results of the preclinical studies reviewed provide evidence for sex differences in stress-induced reinstatement and incubation of cocaine craving but not cue- or cocaine-induced reinstatement of cocaine seeking. These sex differences are modulated in part by ovarian hormones. In contrast, the available data do not support the notion of sex differences in craving and relapse/reinstatement for methamphetamine or opioids in rodent models. SIGNIFICANCE STATEMENT: This systematic review summarizes clinical and preclinical studies on sex differences in psychostimulant and opioid craving and relapse. Results of the clinical studies reviewed do not appear to support the notion that women are more vulnerable to psychostimulant and opioid craving and relapse. Results of preclinical studies reviewed provide evidence for sex differences in reinstatement and incubation of cocaine seeking but not for reinstatement or incubation of methamphetamine or opioid seeking.

Negative symptoms in alcohol use disorder: A pilot study applying the two-factor model of negative symptoms to patients with alcohol use disorder

BACKGROUND AND AIMS

Alcohol Use Disorder (AUD) is characterized by a reduction in goal-directed behavior, with alcohol use taking precedence over other areas of life. These features in AUD resemble negative symptoms in schizophrenia, especially the reduction in motivation and pleasure (MAP). Given the clinical similarities of negative symptoms across diagnostic categories, it comes as a surprise that there are few investigations on negative symptoms in alcohol and other substance use disorders. To our knowledge, our study is the first to assess negative symptoms in AUD based on a two-factorial approach, and to investigate the interrelation of these dimensions with the severity of AUD, and alcohol craving.

MATERIALS AND METHODS

We examined a sample of 42 patients with AUD at the Psychiatric University Hospital in Zurich. Participants provided self-report and interview-based measures of the severity of AUD, negative symptoms, and alcohol craving. Finally, we used data from the electronic health records of the patients.

RESULTS

Patients with AUD show negative symptoms to a similar extent as patients with schizophrenia or bipolar disorder. We found a positive correlation between the extent of impairment within the MAP factor and overall severity of AUD. Furthermore, MAP negative symptoms were correlated with alcohol craving. In a linear regression, negative symptoms predicted alcohol craving whereas depression did not.

SUMMARY

Negative symptoms as conceptualized for schizophrenia are prevalent in patients with AUD and associated with the severity of AUD. More specifically, severity of AUD correlates with diminished motivation and pleasure, highlighting the importance of disturbances in motivational functions in AUD. This is further supported by the correlation between negative symptoms and craving, a hallmark of AUD. Taken together, our findings suggest that negative symptoms might be a highly relevant but hitherto often neglected therapeutic target in AUD.

Psychosocial Factors Predict the Level of Substance Craving of People with Drug Addiction: A Machine Learning Approach

This study aimed to explore which factors had a greater impact on substance craving in people with substance use and the direction of the impact. A total of 895 male substance users completed questionnaires regarding substance craving, psychological security, positive psychological capital, interpersonal trust, alexithymia, impulsivity, parental conflict, aggression behavior, life events, family intimacy, and deviant peers. Calculating the factor importance by gradient boosting method (GBM), found that the psychosocial factors that had a greater impact on substance craving were, in order, life events, aggression behavior, positive psychological capital, interpersonal trust, psychological security, impulsivity, alexithymia, family intimacy, parental conflict, and deviant peers. Correlation analysis showed that life events, positive psychological capital, interpersonal trust, psychological security, and family intimacy negatively predicted substance craving, while aggression behavior, impulsivity, alexithymia, parental conflict, and deviant peers positively predicted substance cravings. These findings have important implications for the prevention and intervention of substance craving behavior among substance users.

Atypical interoception as a common risk factor for psychopathology: A review

The inadequacy of a categorial approach to mental health diagnosis is now well-recognised, with many authors, diagnostic manuals and funding bodies advocating a dimensional, trans-diagnostic approach to mental health research. Variance in interoception, the ability to perceive one's internal bodily state, is reported across diagnostic boundaries, and is associated with atypical functioning across symptom categories. Drawing on behavioural and neuroscientific evidence, we outline current research on the contribution of interoception to numerous cognitive and affective abilities (in both typical and clinical populations), and describe the interoceptive atypicalities seen in a range of psychiatric conditions. We discuss the role that interoception may play in the development and maintenance of psychopathology, as well as the ways in which interoception may differ across clinical presentations. A number of important areas for further research on the role of interoception in psychopathology are highlighted.

Transcranial Direct Current Stimulation Targeting the Ventromedial Prefrontal Cortex Reduces Reactive Aggression and Modulates Electrophysiological Responses in a Forensic Population

BACKGROUND

Studies have shown that impairments in the ventromedial prefrontal cortex play a crucial role in violent behavior in forensic patients who also abuse cocaine and alcohol. Moreover, interventions that aimed to reduce violence risk in those patients are found not to be optimal. A promising intervention might be to modulate the ventromedial prefrontal cortex by high-definition (HD) transcranial direct current stimulation (tDCS). The current study aimed to examine HD-tDCS as an intervention to increase empathic abilities and reduce violent behavior in forensic substance dependent offenders. In addition, using electroencephalography, we examined the effects on the P3 and the late positive potential of the event-related potentials in reaction to situations that depict victims of aggression.

METHODS

Fifty male forensic patients with a substance dependence were tested in a double-blind, placebo-controlled randomized study. The patients received HD-tDCS 2 times a day for 20 minutes for 5 consecutive days. Before and after the intervention, the patients completed self-reports and performed the Point Subtraction Aggression Paradigm, and electroencephalography was recorded while patients performed an empathy task.

RESULTS

Results showed a decrease in aggressive responses on the Point Subtraction Aggression Paradigm and in self-reported reactive aggression in the active tDCS group. Additionally, we found a general increase in late positive potential amplitude after active tDCS. No effects on trait empathy and the P3 were found.

CONCLUSIONS

Current findings are the first to find positive effects of HD-tDCS in reducing aggression and modulating electrophysiological responses in forensic patients, showing the potential of using tDCS as an intervention to reduce aggression in forensic mental health care.

Neurochemical mechanisms and neurocircuitry underlying the contribution of stress to cocaine seeking

In individuals with substance use disorders, stress is a critical determinant of relapse susceptibility. In some cases, stressors directly trigger cocaine use. In others, stressors interact with other stimuli to promote drug seeking, thereby setting the stage for relapse. Here, we review the mechanisms and neurocircuitry that mediate stress-triggered and stress-potentiated cocaine seeking. Stressors trigger cocaine seeking by activating noradrenergic projections originating in the lateral tegmentum that innervate the bed nucleus of the stria terminalis to produce beta adrenergic receptor-dependent regulation of neurons that release corticotropin releasing factor (CRF) into the ventral tegmental area (VTA). CRF promotes the activation of VTA dopamine neurons that innervate the prelimbic prefrontal cortex resulting in D1 receptor-dependent excitation of a pathway to the nucleus accumbens core that mediates cocaine seeking. The stage-setting effects of stress require glucocorticoids, which exert rapid non-canonical effects at several sites within the mesocorticolimbic system. In the nucleus accumbens, corticosterone attenuates dopamine clearance via the organic cation transporter 3 to promote dopamine signaling. In the prelimbic cortex, corticosterone mobilizes the endocannabinoid, 2-arachidonoylglycerol (2-AG), which produces CB1 receptor-dependent reductions in inhibitory transmission, thereby increasing excitability of neurons which comprise output pathways responsible for cocaine seeking. Factors that influence the role of stress in cocaine seeking, including prior history of drug use, biological sex, chronic stress/co-morbid stress-related disorders, adolescence, social variables, and genetics are discussed. Better understanding when and how stress contributes to drug seeking should guide the development of more effective interventions, particularly for those whose drug use is stress related.

Differences in cue-induced brain activation between long-term methadone maintenance treatment and protracted abstinence in heroin use disorder patients: a functional magnetic resonance imaging study

Background

Heroin use disorder (HUD) remains one of the gravest public health issues in China. Methadone maintenance treatment (MMT) and protracted abstinence (PA) are the most commonly used treatments for HUD. Although both treatment approaches can alleviate heroin cravings, a previous study found that MMT patients had stronger cue-induced brain activation than patients undergoing PA; however, the changes associated with long-term treatment are unclear.

Methods

Male patients with HUD who had been undergoing either PA (n=24) or MTT (n=21) for approximately 12 months, together with 20 demographically matched healthy controls, completed an event-related functional magnetic resonance imaging (fMRI) task. The subjective craving for heroin was evaluated using a visual analog scale.

Results

Compared to the healthy controls, the MMT and PA groups demonstrated significantly higher brain activation in the left pallidum, middle occipital gyrus, postcentral gyrus, anterior cingulate cortex, middle cingulate cortex, inferior parietal lobule, superior parietal lobule, amygdala, hippocampus, right inferior temporal gyrus, inferior frontal gyrus triangularis, and caudate during exposure to heroin-related cues. Compared to those undergoing PA, patients in the MMT group demonstrated significantly higher brain activation in all of these regions. Except for the left inferior parietal lobule and left superior parietal lobule, there were no statistically significant differences between the PA and healthy control groups. The MMT patients showed significantly higher subjective cravings before and after exposure to heroin cues than the PA group, but there was no significant difference in the change in subjective cravings between the 2 groups.

Conclusions

The results suggested that although the HUD patients receiving long-term MMT complied with the treatment, they still had higher subjective cravings and cue-induced brain activation than those undergoing PA. Therefore, long-term PA appears to be more beneficial than MMT in reducing the salience value of drug cues in patients with HUD.

Hippocampal mu opioid receptors are modulated following cocaine self-administration in rat

Cocaine addiction is a complex pathology induced by long-term brain changes. Understanding the neurochemical changes underlying the reinforcing effects of this drug of abuse is critical for reducing the societal burden of drug addiction. The mu opioid receptor plays a major role in drug reward. This receptor is modulated by chronic cocaine treatment in specific brain structures, but few studies investigated neurochemical adaptations induced by voluntary cocaine intake. In this study, we investigated whether intravenous cocaine-self administration (0.33 mg/kg/injection, fixed-ratio 1 [FR1], 10 days) in rats induces transcriptional and functional changes of the mu opioid receptor in reward-related brain regions. Epigenetic processes with histone modifications were examined for two activating marks, H3K4Me3, and H3K27Ac. We found an increase of mu opioid receptor gene expression along with a potentiation of its functionality in hippocampus of cocaine self-administering animals compared to saline controls. Chromatin immunoprecipitation followed by qPCR revealed no modifications of the histone mark H3K4Me3 and H3K27Ac levels at mu opioid receptor promoter. Our study highlights the hippocampus as an important target to further investigate neuroadaptive processes leading to cocaine addiction.

Disrupting Reconsolidation by Systemic Inhibition of mTOR Kinase via Rapamycin Reduces Cocaine-Seeking Behavior

Drug addiction is considered maladaptive learning, and drug-related memories aroused by the presence of drug related stimuli (drug context or drug-associated cues) promote recurring craving and reinstatement of drug seeking. The mammalian target of rapamycin signaling pathway is involved in reconsolidation of drug memories in conditioned place preference and alcohol self-administration (SA) paradigms. Here, we explored the effect of mTOR inhibition on reconsolidation of addiction memory using cocaine self-administration paradigm. Rats received intravenous cocaine self-administration training for 10 consecutive days, during which a light/tone conditioned stimulus was paired with each cocaine infusion. After acquisition of the stable cocaine self-administration behaviors, rats were subjected to nosepoke extinction (11 days) to extinguish their behaviors, and then received a 15 min retrieval trial with or without the cocaine-paired tone/light cue delivery or without. Immediately or 6 h after the retrieval trial, rapamycin (10 mg/kg) was administered intraperitoneally. Finally, cue-induced reinstatement, cocaine-priming-induced reinstatement and spontaneous recovery of cocaine-seeking behaviors were assessed in rapamycin previously treated animals, respectively. We found that rapamycin treatment immediately after a retrieval trial decreased subsequent reinstatement of cocaine seeking induced by cues or cocaine itself, and these effects lasted at least for 28 days. In contrast, delayed intraperitoneal injection of rapamycin 6 h after retrieval or rapamycin injection without retrieval had no effects on cocaine-seeking behaviors. These findings indicated that mTOR inhibition within the reconsolidation time-window impairs the reconsolidation of cocaine associated memory, reduces cocaine-seeking behavior and prevents relapse, and these effects are retrieval-dependent and temporal-specific.

Primate ventral striatum maintains neural representations of the value of previously rewarded objects for habitual seeking

The ventral striatum (VS) is considered a key region that flexibly updates recent changes in reward values for habit learning. However, this update process may not serve to maintain learned habitual behaviors, which are insensitive to value changes. Here, using fMRI in humans and single-unit electrophysiology in macaque monkeys we report another role of the primate VS: that the value memory subserving habitual seeking is stably maintained in the VS. Days after object-value associative learning, human and monkey VS continue to show increased responses to previously rewarded objects, even when no immediate reward outcomes are expected. The similarity of neural response patterns to each rewarded object increases after learning among participants who display habitual seeking. Our data show that long-term memory of high-valued objects is retained as a single representation in the VS and may be utilized to evaluate visual stimuli automatically to guide habitual behavior.

Neural Substrates and Circuits of Drug Addiction

Drug addiction is a chronic relapsing disorder, and a significant amount of research has been devoted to understand the factors that contribute to the development, loss of control, and persistence of compulsive addictive behaviors. In this review, we provide an overview of various theories of addiction to drugs of abuse and the neurobiology involved in elements of the addiction cycle. Specific focus is devoted to the role of the mesolimbic pathway in acute drug reinforcement and occasional drug use, the role of the mesocortical pathway and associated areas (e.g., the dorsal striatum) in escalation/dependence, and the contribution of these pathways and associated circuits to conditioned responses, drug craving, and loss of behavioral control that may underlie drug relapse. By enhancing the understanding of the neurobiological factors that mediate drug addiction, continued preclinical and clinical research will aid in the development of novel therapeutic interventions that can serve as effective long-term treatment strategies for drug-dependent individuals.

Medial prefrontal cortical control of reward- and aversion-based behavioral output: Bottom-up modulation

How does the brain guide our actions? This is a complex issue, where the medial prefrontal cortex (mPFC) plays a crucial role. The mPFC is essential for cognitive flexibility and decision making. These functions are related to reward- and aversion-based learning, which ultimately drive behavior. Though, cortical projections and modulatory systems that may regulate those processes in the mPFC are less understood. How does the mPFC regulate approach-avoidance behavior in the case of conflicting aversive and appetitive stimuli? This is likely dependent on the bottom-up neuromodulation of the mPFC projection neurons. In this review, we integrate behavioral-, pharmacological-, and viral-based circuit manipulation data showing the involvement of mPFC dopaminergic, noradrenergic, cholinergic, and serotoninergic inputs in reward and aversion processing. Given that an incorrect balance of reward and aversion value could be a key problem in mental diseases such as substance use disorders, we discuss outstanding questions for future research on the role of mPFC modulation in reward and aversion.

Noradrenergic correlates of chronic cocaine craving: neuromelanin and functional brain imaging

Preclinical studies have implicated noradrenergic (NA) dysfunction in cocaine addiction. In particular, the NA system plays a central role in motivated behavior and may partake in the regulation of craving and drug use. Yet, human studies of the NA system are scarce, likely hampered by the difficulty in precisely localizing the locus coeruleus (LC). Here, we used neuromelanin imaging to localize the LC and quantified LC neuromelanin signal (NMS) intensity in 44 current cocaine users (CU; 37 men) and 59 nondrug users (NU; 44 men). We also employed fMRI to investigate cue-induced regional responses and LC functional connectivities, as quantified by generalized psychophysiological interaction (gPPI), in CU. Imaging data were processed by published routines and the findings were evaluated with a corrected threshold. We examined how these neural measures were associated with chronic cocaine craving, as assessed by the Cocaine Craving Questionnaire (CCQ). Compared to NU, CU demonstrated higher LC NMS for all probabilistic thresholds defined of 50-90% of the peak. In contrast, NMS of the ventral tegmental area/substantia nigra (VTA/SN) did not show significant group differences. Drug as compared to neutral cues elicited higher activations of many cortical and subcortical regions, none of which were significantly correlated with CCQ score. Drug vs. neutral cues also elicited "deactivation" of bilateral parahippocampal gyri (PHG) and PHG gPPI with a wide array of cortical and subcortical regions, including the ventral striatum and, with small volume correction, the LC. Less deactivation of the PHG (r = 0.40, p = 0.008) and higher PHG-LC gPPI (r = 0.44, p = 0.003) were positively correlated with the CCQ score. In contrast, PHG-VTA/SN connectivity did not correlate with the CCQ score. Together, chronic cocaine exposure may induce higher NMS intensity, suggesting neurotoxic effects on the LC. The correlation of cue-elicited PHG LC connectivity with CCQ score suggests a noradrenergic correlate of chronic cocaine craving. Potentially compensating for memory functions as in neurodegenerative conditions, cue-elicited PHG LC circuit connectivity plays an ill-adaptive role in supporting cocaine craving.

Bidirectional causality between addiction and cognitive deficits

Cognitive deficits are highly comorbid with substance use disorders. Deficits span multiple cognitive domains, are associated with disease severity across substance classes, and persist long after cessation of substance use. Furthermore, recovery of cognitive function during protracted abstinence is highly predictive of treatment adherence, relapse, and overall substance use disorder prognosis, suggesting that addiction may be best characterized as a disease of executive dysfunction. While the association between cognitive deficits and substance use disorders is clear, determining causalities is made difficult by the complex interplay between these variables. Cognitive dysfunction present prior to first drug use can act as a risk factor for substance use initiation, likelihood of pathology, and disease trajectory. At the same time, substance use can directly cause cognitive impairments even in individuals without preexisting deficits. Thus, parsing preexisting risk factors from substance-induced adaptations, and how they may interact, poses significant challenges. Here, focusing on psychostimulants and alcohol, we review evidence from clinical literature implicating cognitive deficits as a risk factor for addiction, a consequence of substance use, and the role the prefrontal cortex plays in these phenomena. We then review corresponding preclinical literature, highlighting the high degree of congruency between animal and human studies, and emphasize the unique opportunity that animal models provide to test causality between cognitive phenotypes and substance use, and to investigate the underlying neurobiology at a cellular and molecular level. Together, we provide an accessible resource for assessing the validity and utility of forward- and reverse-translation between these clinical and preclinical literatures.

Hippocampal-Dependent Inhibitory Learning and Memory Processes in the Control of Eating and Drug Taking

As manifestations of excessive and uncontrolled intake, obesity and drug addiction have generated much research aimed at identifying common neuroadaptations that could underlie both disorders. Much work has focused on changes in brain reward and motivational circuitry that can overexcite eating and drug-taking behaviors. We suggest that the regulation of both behaviors depends on balancing excitation produced by stimuli associated with food and drug rewards with the behavioral inhibition produced by physiological "satiety" and other stimuli that signal when those rewards are unavailable. Our main hypothesis is that dysregulated eating and drug use are consequences of diet- and drug-induced degradations in this inhibitory power. We first outline a learning and memory mechanism that could underlie the inhibition of both food and drug-intake, and we describe data that identifies the hippocampus as a brain substrate for this mechanism. We then present evidence that obesitypromoting western diets (WD) impair the operation of this process and generate pathophysiologies that disrupt hippocampal functioning. Next, we present parallel evidence that drugs of abuse also impair this same learning and memory process and generate similar hippocampal pathophysiologies. We also describe recent findings that prior WD intake elevates drug self-administration, and the implications of using drugs (i.e., glucagon-like peptide- 1 agonists) that enhance hippocampal functioning to treat both obesity and addiction are also considered. We conclude with a description of how both WD and drugs of abuse could initiate a "vicious-cycle" of hippocampal pathophysiology and impaired hippocampal-dependent behavioral inhibition.

The Cerebellum on Cocaine

The traditional cerebellum’s role has been linked to the high computational demands for sensorimotor control. However, several findings have pointed to its involvement in executive and emotional functions in the last decades. First in 2009 and then, in 2016, we raised why we should consider the cerebellum when thinking about drug addiction. A decade later, mounting evidence strongly suggests the cerebellar involvement in this disorder. Nevertheless, direct evidence is still partial and related mainly to drug-induced reward memory, but recent results about cerebellar functions may provide new insights into its role in addiction. The present review does not intend to be a compelling revision on available findings, as we did in the two previous reviews. This minireview focuses on specific findings of the cerebellum’s role in drug-related reward memories and the way ahead for future research. The results discussed here provide grounds for involving the cerebellar cortex’s apical region in regulating behavior driven by drug-cue associations. They also suggest that the cerebellar cortex dysfunction may facilitate drug-induced learning by increasing glutamatergic output from the deep cerebellar nucleus (DCN) to the ventral tegmental area (VTA) and neural activity in its projecting areas.

Behavioral and neurobiological alterations induced by chronic use of crack cocaine

Crack cocaine is the crystal form of cocaine and can be smoked, and rapidly absorbed, and, in part for this reason, is potently addictive. It is hypothesized that crack cocaine is able to induce important changes in different tissues and organs, and thus dramatically alter behavior. Nevertheless, which alterations in the central nervous system are related to its frequent use is still a matter of discussion. The present study is a literature review of articles published between the years 2008 and 2018 on the theme 'crack cocaine and brain' available in PUBMED, MEDLINE, EMBASE, and Google scholar databases. The results show that the use of crack cocaine induces important behavioral, neuroanatomical, and biochemical alterations. The main behavioral sequelae include cognitive and emotional changes, such as increased anxiety and depressive symptoms, attention and memory deficits, and hyperactivity. Among the neurobiological alterations are reductions in the activity of the prefrontal, anterior cingulate cortex, and nucleus accumbens. Molecular changes include decreases in neurotrophic factors and increases in oxidative stress and inflammatory cytokines, which may be responsible for the morphological alterations observed. It is also hypothesized that these neurobiological changes might explain the emotional and cognitive dysfunctions experienced by crack cocaine addicts.

Neuroplastic changes in resting-state functional connectivity after rTMS intervention for methamphetamine craving

Amphetamine-type stimulants are the second most commonly abused illicit drug worldwide, with no effective medical treatments currently available. Previous studies have demonstrated that high frequency repetitive transcranial magnetic stimulation (rTMS) over the left dorsolateral prefrontal cortex (DLPFC) reduced cue-induced craving in patients with methamphetamine dependence. However, the neuroplastic mechanism underlying rTMS intervention in methamphetamine users remains to be elucidated. Sixty participants (40 males) with severe methamphetamine use disorder according to DSM-5 were randomized to receive either intermittent theta burst protocols (iTBS) (short bursts of 50 Hz rTMS repeated at a rate in the theta range (5 Hz), 2-sec on, 8-sec off for 5 min; 900 pulses) or sham rTMS over the DLPFC over four weeks (20 daily sessions). Resting state functional connectivity magnetic resonance imaging was acquired before and after rTMS intervention. Participants received drug related cue exposure and rated their craving before and after stimulation. Seed-based functional connectivity analysis was performed to probe rTMS-induced neuroplastic reorganization of brain functional networks. Results showed that twenty daily rTMS sessions decreased craving, increased functional connectivity between left DLPFC and inferior parietal lobule, and decreased functional connectivity between insula and inferior parietal lobule, medial temporal lobe and precuneus. Moreover, the increase of functional connectivity between DLPFC and inferior parietal lobule correlated with craving reduction. This study suggests that neuroplastic changes of frontoparietal functional connectivity contributes to craving reduction, shedding light on the therapeutic effect of rTMS on methamphetamine use disorder. This article is part of the special issue on Stress, Addiction and Plasticity.

Glycogen synthase kinase-3 signaling in cellular and behavioral responses to psychostimulant drugs

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase implicated in numerous physiological processes and cellular functions through its ability to regulate the function of many proteins, including transcription factors and structural proteins. GSK-3β has been demonstrated to function as a regulator of multiple behavioral processes induced by drugs of abuse, particularly psychostimulant drugs. In this review, we provide an overview of the regulation of GSK-3β activity produced by psychostimulants, and the role of GSK-3β signaling in psychostimulant-induced behaviors including drug reward, associative learning and memory which play a role in the maintenance of drug-seeking. Evidence supports the conclusion that GSK-3β is an important component of the actions of psychostimulant drugs and that GSK-3β is a valid target for developing novel therapeutics. Additional studies are required to examine the role of GSK-3β in distinct cell types within the mesolimbic and memory circuits to further elucidate the mechanisms related to the acquisition, consolidation, and recall of drug-related memories, and potentially countering neuroadaptations that reinforce drug-seeking behaviors that maintain drug dependence.

Altered subcallosal and posterior cingulate cortex-based functional connectivity during smoking cue and mental simulation processing in smokers

BACKGROUND

Long-term cigarette smoking induces sensitization of incentive salience and conditioning of contextual cues which involves brain function alteration across multiple regions. Understanding how nicotine affects hub-based functional connectivities involved in affective and cognitive function can help us determine the treatment strategy for nicotine dependence.

METHOD

Functional MRI was conducted on 30 smokers and 30 non-smokers while mentally simulating neutral and smoking hand movements. Smoking cue and mental simulation processing-related changes in functional connectivity strengths of the subcallosal and posterior cingulate cortex (SCC and PCC) with major brain network nodes were examined.

RESULTS

Compared to non-smokers, smokers showed cue-induced SCC functional connectivities which were enhanced with the intraparietal sulcus and reduced with the medial prefrontal cortex. The PCC activation and functional connectivity enhancements with the anterior insula cortex and rostro-lateral prefrontal cortex was found during smoking mental simulation. The PCC-lateral prefrontal cortex functional connectivity correlated with nicotine dependence severity.

CONCLUSION

The present results demonstrate that smokers can be identified by cue-induced SCC functional connectivity strength decline and increment in the default mode and dorsal attention network nodes. However, nicotine dependence was associated with smoking mental simulation-related PCC-lateral prefrontal cortex functional connectivity strength, suggesting that the development of nicotine dependence may depend on the strength of coupling between the default mode network and the central executive network at the cognitive level.

Alcohol usage predicts holistic perception: A novel method for exploring addiction

Holistic perception is a special form of automatic and experience dependent processing that prioritises objects of interest through the visual system. We therefore speculated that higher levels of alcohol consumption may be associated with enhanced holistic perception for alcohol cues. In our first experiment, we confirmed this hypothesis by showing that increasing regular alcohol usage was associated with greater holistic perception of alcohol, but not non-alcohol, cues. We replicated this finding in a second experiment, but confirmed drink-specific holistic perception for lager cues was not predicted by experience with that drink, but general alcohol usage. In our final experiment when alcohol images were absent from the task, higher levels of alcohol consumption predicted decreased holistic perception for non-rewarding cues. Alcohol use is therefore linked to inverse alterations in holistic perception for alcohol versus non-alcohol cues, with the latter's effects context dependent. We hypothesise that such inverse relationships may be due to limited cortical resources becoming reutilised for alcohol cues at the expense of other stimuli. Future work will be required to determine holistic perception's role in maintaining addiction, its predictive value in successful abstinence, and its relationship with characteristics of addiction such as cue reactivity, attentional biases and personality traits.

Pharmacological NOS-1 Inhibition Within the Hippocampus Prevented Expression of Cocaine Sensitization: Correlation with Reduced Synaptic Transmission

Behavioral sensitization to psychostimulants hyperlocomotor effect is a useful model of addiction and craving. Particularly, cocaine sensitization in rats enhanced synaptic plasticity within the hippocampus, an important brain region for the associative learning processes underlying drug addiction. Nitric oxide (NO) is a neurotransmitter involved in both, hippocampal synaptic plasticity and cocaine sensitization. It has been previously demonstrated a key role of NOS-1/NO/sGC/cGMP signaling pathway in the development of cocaine sensitization and in the associated enhancement of hippocampal synaptic plasticity. The aim of the present investigation was to determine whether NOS-1 inhibition after development of cocaine sensitization was able to reverse it, and to characterize the involvement of the hippocampus in this phenomenon. Male Wistar rats were administered only with cocaine (15 mg/kg/day i.p.) for 5 days. Then, animals received 7-nitroindazole (NOS-1 inhibitor) either systemically for the next 5 days or a single intra-hippocampal administration. Development of sensitization and its expression after withdrawal were tested, as well as threshold for long-term potentiation in hippocampus, NOS-1, and CREB protein levels and gene expression. The results showed that NOS-1 protein levels and gene expression were increased only in sensitized animals as well as CREB gene expression. NOS-1 inhibition after sensitization reversed behavioral expression and the highest level of hippocampal synaptic plasticity. In conclusion, NO signaling within the hippocampus is critical for the development and expression of cocaine sensitization. Therefore, NOS-1 inhibition or NO signaling pathways interferences during short-term withdrawal after repeated cocaine administration may represent plausible pharmacological targets to prevent or reduce susceptibility to relapse.

Oxytocin-Induced Changes in Intrinsic Network Connectivity in Cocaine Use Disorder: Modulation by Gender, Childhood Trauma, and Years of Use

Cocaine use disorder (CUD) is a major public health concern with devastating social, economic, and mental health implications. A better understanding of the underlying neurobiology and phenotypic variations in individuals with CUD is necessary for the development of effective and targeted treatments. In this study, 39 women and 54 men with CUD completed a 6-min resting-state functional magnetic resonance imaging scan after intranasal oxytocin (OXY) or placebo administration. Graph-theory network analysis was used to quantify functional connectivity changes caused by OXY in striatum, anterior cingulate cortex (ACC), insula, and amygdala nodes of interest. OXY increased connectivity in the right ACC and left amygdala in males, whereas OXY increased connectivity in the right ACC and right accumbens in females. Machine learning was then used to associate treatment response (placebo minus OXY) in nodes of interest with years of cocaine use and severity of childhood trauma separately for males and females. Childhood trauma and years of cocaine use were associated with OXY-induced changes in ACC connectivity for both men and women, but connectivity changes in the amygdala were associated with years of cocaine use in men and connectivity changes in the right insula were associated with years of cocaine use in women. These findings suggest that salience network nodes (ACC and insula) are potential OXY treatment targets in CUD, with the amygdala as a treatment target for men and the accumbens as a treatment target for women.

A medium throughput rodent model of relapse from addiction with behavioral and pharmacological specificity

One of most formidable problems in the treatment of addiction is the high rate of relapse. The discovery of medicines to help mitigate relapse are aided by animal models that currently involve weeks of training and require surgical preparations and drug delivery devices. The present set of experiments was initiated to investigate a rapid 8-day screening method that utilizes food instead of intravenous drug administration. Male Sprague-Dawley rats were trained in a reinstatement paradigm in which every lever press produced a 45 mg food pellet concurrently paired with a light and tone. Behavior was subsequently extinguished with lever responses producing neither food nor food-associated stimuli. Reinstatement of responding was evaluated under conditions in which the first three responses of every 5 min time bin produced a food pellet along with food-associated stimuli. The mGlu₅ receptor antagonists MPEP and MTEP produced a significant reduction in reinstatement while failing to alter responding where every response produced food. The cannabinoid CB₁ receptor antagonist rimonabant and the mGlu_2/3 receptor agonist LY379268 also selectively reduced reinstatement. Other compounds including clozapine, d-amphetamine, chlordiazepoxide, ABT-431, naltrexone and citalopram were without effect. The results suggest that relapse-like behavioral effects can be extended to non-pharmacological reinforcers. Drug effects demonstrated both behavioral and pharmacological specificity. The present experimental design thus allows for efficient and rapid assessment of the effects of drugs that might be useful in the treatment of addiction-associated relapse.

Image-guided cranial irradiation-induced ablation of dentate gyrus neurogenesis impairs extinction of recent morphine reward memories

Dentate gyrus adult neurogenesis is implicated in the formation of hippocampal-dependent contextual associations. However, the role of adult neurogenesis during reward-based context-dependent paradigms-such as conditioned place preference (CPP)-is understudied. Therefore, we used image-guided, hippocampal-targeted X-ray irradiation (IG-IR) and morphine CPP to explore whether dentate gyrus adult neurogenesis plays a role in reward memories created in adult C57BL/6J male mice. In addition, as adult neurogenesis appears to participate to a greater extent in retrieval and extinction of recent (<48 hr posttraining) versus remote (>1 week posttraining) memories, we specifically examined the role of adult neurogenesis in reward-associated contextual memories probed at recent and remote timepoints. Six weeks post-IG-IR or Sham treatment, mice underwent morphine CPP. Using separate groups, retrieval of recent and remote reward memories was found to be similar between IG-IR and Sham treatments. Interestingly, IG-IR mice showed impaired extinction-or increased persistence-of the morphine-associated reward memory when it was probed 24-hr (recent) but not 3-weeks (remote) postconditioning relative to Sham mice. Taken together, these data show that hippocampal-directed irradiation and the associated decrease in dentate gyrus adult neurogenesis affect the persistence of recently-but not remotely-probed reward memory. These data indicate a novel role for adult neurogenesis in reward-based memories and particularly the extinction rate of these memories. Consideration of this work may lead to better understanding of extinction-based behavioral interventions for psychiatric conditions characterized by dysregulated reward processing.

Mental imagery in psychiatry: conceptual & clinical implications

Mental imagery refers to the experience of perception in the absence of external sensory input. Deficits in the ability to generate mental imagery or to distinguish it from actual sensory perception are linked to neurocognitive conditions such as dementia and schizophrenia, respectively. However, the importance of mental imagery to psychiatry extends beyond neurocognitive impairment. Mental imagery has a stronger link to emotion than verbal-linguistic cognition, serving to maintain and amplify emotional states, with downstream impacts on motivation and behavior. As a result, anomalies in the occurrence of emotion-laden mental imagery has transdiagnostic significance for emotion, motivation, and behavioral dysfunction across mental disorders. This review aims to demonstrate the conceptual and clinical significance of mental imagery in psychiatry through examples of mood and anxiety disorders, self-harm and suicidality, and addiction. We contend that focusing on mental imagery assessment in research and clinical practice can increase our understanding of the cognitive basis of psychopathology in mental disorders, with the potential to drive the development of algorithms to aid treatment decision-making and inform transdiagnostic treatment innovation.