Differences in "bottom-up" and "top-down" neural activity in current and former cigarette smokers: Evidence for neural substrates which may promote nicotine abstinence through increased cognitive control

The Brain Salience Network at the Intersection of Pain and Substance use Disorders: Insights from Functional Neuroimaging Research

Purpose of Review

The brain's salience network (SN), primarily comprising the anterior insula and anterior cingulate cortex, plays a key role in detecting salient stimuli and processing physical and socioemotional pain (e.g., social rejection). Mounting evidence underscores an altered SN in the etiology and maintenance of substance use disorders (SUDs). This paper aims to synthesize recent functional neuroimaging research emphasizing the SN's involvement in SUDs and physical/socioemotional pain and explore the therapeutic prospects of targeting the SN for SUD treatment.

Recent Findings

The SN is repeatedly activated during the experience of both physical and socioemotional pain. Altered activation within the SN is associated with both SUDs and chronic pain conditions, characterized by aberrant activity and connectivity patterns as well as structural changes. Among individuals with SUDs, functional and structural alterations in the SN have been linked to abnormal salience attribution (e.g., heightened responsiveness to drug-related cues), impaired cognitive control (e.g., impulsivity), and compromised decision-making processes. The high prevalence of physical and socioemotional pain in the SUD population may further exacerbate SN alterations, thus contributing to hindered recovery progress and treatment failure. Interventions targeting the restoration of SN functioning, such as real-time functional MRI feedback, neuromodulation, and psychotherapeutic approaches, hold promise as innovative SUD treatments.

Summary

The review highlights the significance of alterations in the structure and function of the SN as potential mechanisms underlying the co-occurrence of SUDs and physical/socioemotional pain. Future work that integrates neuroimaging with other research methodologies will provide novel insights into the mechanistic role of the SN in SUDs and inform the development of next-generation treatment modalities.

Dissociation of drug and negative emotional cue induced attentional bias in individuals with methamphetamine-use disorder

BACKGROUND AND OBJECTIVES

Although both drugs and negative emotions can trigger drug craving or relapse in individuals with methamphetamine-use disorder (MUD), it remains unclear whether individuals with MUD have attentional biases toward both drug and negative emotional cues and whether this bias involves attention orientation or difficulty in attention disengagement. This study aimed to measure different components of attentional bias toward drug-related and negative emotional cues in individuals with MUD.

METHODS

Two dot-probe tasks were used to investigate attentional bias toward drug (drug task) and negative emotional cues (emotion task) in individuals with MUD. Forty-three males with MUD (average age of 43.44 ± 11.91 years, average drug-use duration of 11.35 ± 8.39 years) participated in the study voluntarily.

RESULTS

There was a significant interaction between the task type and location (p = .01). Specifically, for drug cues, participants showed significant difficulty in attention disengagement toward drug cues (p = .01); however, no attention orientation (p = .46). For negative emotional cues, neither significant attention orientation (p = .07) nor significant difficulty in attention disengagement (p = .50) was found.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

Attentional bias in individuals with MUD was highly selective for drug cues; thus, difficulty in attention disengagement from drug cues can be considered a potential mediating mechanism for attentional bias modification interventions for individuals with MUD. This study served to generate hypotheses or suggest future experiments on interventions for individuals with MUD.

Similarity and difference in large-scale functional network alternations between behavioral addictions and substance use disorder: a comparative meta-analysis

Behavioral addiction (BA) and substance use disorder (SUD) share similarities and differences in clinical symptoms, cognitive functions, and behavioral attributes. However, little is known about whether and how functional networks in the human brain manifest commonalities and differences between BA and SUD. Voxel-wise meta-analyses of resting-state functional connectivity (rs-FC) were conducted in BA and SUD separately, followed by quantitative conjunction analyses to identify the common and distinct alterations across both the BA and SUD groups. A total of 92 datasets with 2444 addicted patients and 2712 healthy controls (HCs) were eligible for the meta-analysis. Our findings demonstrated that BA and SUD exhibited common alterations in rs-FC between frontoparietal network (FPN) and other high-level neurocognitive networks (i.e. default mode network (DMN), affective network (AN), and salience network (SN)) as well as hyperconnectivity between SN seeds and the Rolandic operculum in SSN. In addition, compared with BA, SUD exhibited several distinct within- and between-network rs-FC alterations mainly involved in the DMN and FPN. Further, altered within- and between-network rs-FC showed significant association with clinical characteristics such as the severity of addiction in BA and duration of substance usage in SUD. The common rs-FC alterations in BA and SUD exhibited the relationship with consistent aberrant behaviors in both addiction groups, such as impaired inhibition control and salience attribution. By contrast, the distinct rs-FC alterations might suggest specific substance effects on the brain neural transmitter systems in SUD.

Neural underpinnings of response inhibition in substance use disorders: weak meta-analytic evidence for a widely used construct

RATIONALE

Substance use disorders (SUDs) rank among the most severely debilitating psychiatric conditions. Among others, decreased response inhibition capacities could make it more difficult for patients to abstain from drug use and maintain abstinence. However, meta-analyses on the neural basis of response inhibition in SUDs yielded conflicting results.

OBJECTIVE

In this study, we revisited the neuroimaging research field and summarized the existing fMRI literature on overt response inhibition (Go/NoGo and stop-signal paradigms) across different SUDs.

METHODS

We performed a systematic literature review and an activation likelihood estimation (ALE) meta-analysis to investigate the actual convergence of functional deviations observed in SUD samples. Results were further supplied by consecutive robustness measures and a post-hoc random-effects meta-analysis of behavioural data.

RESULTS

We identified k = 21 eligible studies for our analysis. The ALE analysis indicated a significant cluster of convergence with its statistical peak in the right anterior insula. Consecutive analyses, however, indicated this result was not robust and susceptible towards publication bias. Additionally, a post-hoc random effects meta-analysis of the behavioural parameters of Go/NoGo and stop-signal paradigms reported by the included studies revealed no significant differences in task performance comparing SUD samples and controls.

CONCLUSION

We discuss that the role of task-based response inhibition may require some refinement as an overarching marker for SUD pathology. Finally, we give a few prospects for future research that should be further explored in this context.

Functional Domains of Substance Use and their Implications to Trauma: A Systematic Review of Neuroimaging Studies

Substance use disorder (SUD) is a significant health problem, and trauma exposure is a known risk factor for the escalation of substance use. However, the shared neural mechanisms through which trauma is associated with substance use are still unknown. Therefore, we systematically review neuroimaging studies focusing on three domains that may contribute to the overlapping mechanisms of SUD and trauma-reward salience, negative emotionality, and inhibition. Using PRISMA guidelines, we identified 45 studies utilizing tasks measuring these domains in alcohol, tobacco, and cannabis use groups. Greater reward, lesser regulation of inhibitory processes, and mixed findings of negative emotionality processes in individuals who use substances versus controls were found. Specifically, greater orbitofrontal cortex, ventral tegmental area, striatum, amygdala, and hippocampal activation was found in response to reward-related tasks, and reduced activation was found in the inferior frontal gyrus and hippocampus in response to inhibition-related tasks. Importantly, no studies in trauma-exposed individuals met our review criteria. Future studies examining the role of trauma-related factors are needed, and more studies should explore inhibition- and negative-emotionality domains in individuals who use substances to uncover clinically significant alterations in these domains that place an individual at greater risk for developing a SUD.

Effects of Hyperdirect Pathway Theta Burst Transcranial Magnetic Stimulation on Inhibitory Control, Craving, and Smoking in Adults With Nicotine Dependence: A Double-Blind, Randomized Crossover Trial

BACKGROUND

Nicotine dependence is associated with dysregulated hyperdirect pathway (HDP)-mediated inhibitory control (IC). However, there are currently no evidence-based treatments that have been shown to target the HDP to improve IC and reduce cigarette cravings and smoking.

METHODS

Following a baseline nonstimulation control session, this study (N = 37; female: n = 17) used a double-blind, randomized crossover design to examine the behavioral and neural effects of intermittent theta burst stimulation (iTBS) and continuous TBS (cTBS) to the right inferior frontal gyrus (rIFG)-a key cortical node of the HDP. Associations between treatment effects were also explored.

RESULTS

At baseline, HDP IC task-state functional connectivity was positively associated with IC task performance, which confirmed the association between HDP circuit function and IC. Compared with iTBS, rIFG cTBS improved IC task performance. Compared with the baseline nonstimulation control session, both TBS conditions reduced cigarette craving and smoking; however, although craving and smoking were lower for cTBS, no differences were found between the two active conditions. In addition, although HDP IC task-state functional connectivity was greater following cTBS than iTBS, there was no significant difference between conditions. Finally, cTBS-induced improvement in IC task performance was associated with reduced craving, and cTBS-induced reduction in craving was associated with reduced smoking.

CONCLUSIONS

These findings warrant further investigation into the effects of rIFG cTBS for increasing IC and reducing craving and smoking among individuals with nicotine dependence. Future sham-controlled cTBS studies may help further elucidate the mechanisms by which rIFG cTBS mediates IC and smoking behavior.

Frontal tDCS reduces alcohol relapse rates by increasing connections from left dorsolateral prefrontal cortex to addiction networks

BACKGROUND

Brain-based interventions are needed to address persistent relapse in alcohol use disorder (AUD). Neuroimaging evidence suggests higher frontal connectivity as well as higher within-network connectivity of theoretically defined addiction networks are associated with reduced relapse rates and extended abstinence during follow-up periods.

OBJECTIVE

/Hypothesis: A longitudinal randomized double-blind sham-controlled clinical trial investigated whether a non-invasive neuromodulation intervention delivered during early abstinence can (i) modulate connectivity of addiction networks supporting abstinence and (ii) improve relapse rates.

HYPOTHESES

Active transcranial direct current stimulation (tDCS) will (i) increase connectivity of addiction networks known to support abstinence and (ii) reduce relapse rates.

METHODS

Short-term abstinent AUD participants (n = 60) were assigned to 5 days of either active tDCS or sham during cognitive training. Causal discovery analysis (CDA) examined the directional influence from left dorsolateral prefrontal cortex (LDLPFC, stimulation site) to addiction networks that support abstinence.

RESULTS

Active tDCS had an effect on the average strength of CDA-determined connectivity from LDLPFC to the incentive salience and negative emotionality addiction networks - increasing in the active tDCS group only. Active tDCS had an effect on relapse rates following the intervention, with lower probability of relapse in the active tDCS vs. sham. Active tDCS showed an unexpected sex-dependent effect on relapse rates.

CONCLUSION

Our results suggest that LDLPFC stimulation delivered during early abstinence has an effect on addiction networks supporting abstinence and on relapse rates. The unexpected sex-dependent neuromodulation effects need to be further examined in larger clinical trials.

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.

Impaired cognitive control moderates the relation between the attribution of incentive salience and severity of consumption in patients with methamphetamine dependence

BACKGROUND

Cognitive control and the attribution of incentive salience are two key neuropsychological processes proposed to explain substance use disorder (SUD). However, little is known about how they interact to influence the severity of drug use in people with SUD.

OBJECTIVE

To determine if cognitive control exerts a moderating effect on the relation between the attribution of salience to drug/reward-related cues and the severity of drug use in SUD cases.

METHOD

Sixty-nine SUD cases with methamphetamine as the main drug of consumption were selected and evaluated. Participants performed the Stroop, Go/No-Go, and Flanker tasks to identify a latent cognitive control factor, and the Effort-Expenditure for Reward task, as well as answering the Methamphetamine Incentive Salience Questionnaire to measure the attribution of incentive salience. Severity of drug use was determined by the KMSK scale and an exploratory clinical interview.

RESULTS

As expected, higher incentive salience attribution predicted greater severity of methamphetamine use. Unexpectedly, however, we found a moderating effect of impaired cognitive control on the relations between higher incentive salience scores and higher monthly drug use, and between younger age at onset of systematic drug use and higher incentive salience scores.

CONCLUSION

Results show the moderating role of cognitive control on the relation between incentive salience attribution and severity of drug use in SUD cases, and help explain the chronic, relapsing nature of addiction, knowledge necessary to develop more precise prevention and treatment strategies.

Reward and inhibition in obesity and cigarette smoking: Neurobiological overlaps and clinical implications

Cigarette smoking and obesity are the leading causes of premature morbidity and mortality and increase the risk of all-cause mortality four-fold when comorbid. Individuals with these conditions demonstrate neurobiological and behavioral differences regarding how they respond to rewarding stimuli or engage in inhibitory control. This narrative review examines the role of reward and inhibition in cigarette smoking and obesity independently, as well as recent research demonstrating an effect of increased body mass index (BMI) on neurocognitive function in individuals who smoke. It is possible that chronic smoking and overeating of highly palatable food, contributing to obesity, dysregulates reward neurocircuitry, subsequently leading to hypofunction of brain networks associated with inhibitory control. These brain changes do not appear to be specific to food or nicotine and, as a result, can potentiate continued cross-use. Changes to reward and inhibitory function due to increased BMI may also make cessation more difficult for those comorbid for obesity and smoking.

Prepared and reactive inhibition in smokers and non-smokers

INTRODUCTION

Models of addiction have identified deficits in inhibitory control, or the ability to inhibit inappropriate or unwanted behaviors, as one factor in the development and maintenance of addictive behaviors. Current literature supports disruption of the prefrontal circuits that mediate reactive inhibitory control processes (i.e., inhibition in response to sudden, unplanned changes in environmental demands) in substance use disorders. However, the relationship between disorders of addiction, such as nicotine dependence, and planned inhibitory processes (i.e., inhibition that occurs after advance warning) is unclear. The goal of the present study was to examine the extent to which reactive and planned inhibitory processes are differentially disrupted in nicotine dependent individuals.

METHOD

We employed an internet-based novel stop signal task wherein participants were instructed to stop a continuous movement at either a predictable or unpredictable time. This task explicitly separated planned and reactive inhibitory processes and assessed group differences in task performance between smokers (N = 281) and non-smokers (N = 164). The smoker group was defined as any participant that identified as a smoker and reported an average daily nicotine consumption of at least 2 mg. The non-smoker group was defined as any participant that identified as a non-smoker and had not been a former smoker that quit within the last year. The smoker group also completed a questionnaire regarding smoking behaviors which included the Fägerstrom Test of Nicotine Dependence (FTND). We used these data to assess the continuous relation between planned stopping, unplanned stopping, and smoking behaviors.

RESULTS

We found significant differences in stop times for both reactive and planned stopping between groups as well as within the smoker group. Additionally, in the smoker group, dependence as measured by the FTND was associated with longer stop times on planned stop trials. Surprisingly, greater daily average consumption of nicotine was related to faster stopping for both trial types.

CONCLUSION

These results indicate the relevance of measuring both reactive and planned inhibitory processes for elucidating the relationship between nicotine addiction and mechanisms of inhibitory control.

The Neural Signature of Impaired Inhibitory Control in Individuals with Heroin Use Disorder

Heroin addiction imposes a devastating toll on society, with little known about its neurobiology. Excessive salience attribution to drug over nondrug cues/reinforcers, with concomitant inhibitory control decreases, are common mechanisms underlying drug addiction. Although inhibitory control alterations generally culminate in prefrontal cortex (PFC) hypoactivations across drugs of abuse, patterns in individuals with heroin addiction (iHUDs) remain unknown. We used a stop-signal fMRI task designed to meet recent consensus guidelines in mapping inhibitory control in 41 iHUDs and 24 age- and sex-matched healthy controls (HCs). Despite group similarities in the stop-signal response time (SSRT; the classic inhibitory control measure), compared with HCs, iHUDs exhibited impaired target detection sensitivity (proportion of hits in go vs false alarms in stop trials; p = 0.003). Additionally, iHUDs exhibited lower right anterior PFC (aPFC) and dorsolateral PFC (dlPFC) activity during successful versus failed stops (the hallmark inhibitory control contrast). Lower left dlPFC/supplementary motor area (SMA) activity was associated with slower SSRT specifically in iHUDs and lower left aPFC activity with worse target sensitivity across all participants (p < 0.05 corrected). Importantly, in iHUDs, lower left SMA and aPFC activity during inhibitory control was associated with shorter time since last use and higher severity of dependence, respectively (p < 0.05 corrected). Together, results revealed lower perceptual sensitivity and hypoactivations during inhibitory control in cognitive control regions (e.g., aPFC, dlPFC, SMA) as associated with task performance and heroin use severity measures in iHUDs. Such neurobehavioral inhibitory control deficits may contribute to self-control lapses in heroin addiction, constituting targets for prevention and intervention efforts to enhance recovery.SIGNIFICANCE STATEMENT Heroin addiction continues its deadly impact, with little known about the neurobiology of this disorder. Although behavioral and prefrontal cortical impairments in inhibitory control characterize addiction across drugs of abuse, these patterns remain underexplored in heroin addiction. Here, we illustrate a significant behavioral impairment in target discrimination in individuals with heroin addiction compared with matched healthy controls. We further show lower engagement during inhibitory control in the anterior and dorsolateral prefrontal cortex (key regions that regulate cognitive control) as associated with slower stopping, worse discrimination, and heroin use measures. Mapping the neurobiology of inhibitory control in heroin addiction for the first time, we identify potential treatment targets inclusive of prefrontal cortex-mediated cognitive control amenable for neuromodulation en route to recovery.

Increased resting-state alpha coherence and impaired inhibition control in young smokers

Exposure to nicotine is the first cause of entirely preventable death killing, which is commonly initiated in adolescence. Previous studies revealed the changes of electroencephalography (EEG) and inhibition control in smokers. However, little is known about the specific link between alpha coherence during the resting state and inhibition control ability in young smokers. The present study aimed to investigate inter-hemispherical and frontal-parietal alpha coherence changes and assessed the relationships between alpha coherence and inhibition control in young smokers. We collected resting-state EEG data from 23 young smokers and 24 healthy controls. Inhibition control ability was assessed by a Go/NoGo task. Compared to healthy controls, young smokers exhibited increased inter-hemispherical and frontal-parietal alpha coherence. Furthermore, young smokers committed more NoGo errors in the Go/NogGo task. It is noteworthy that alpha coherence at the frontal electrode sites was positively correlated with NoGo errors in healthy controls, whereas inverse correlations were observed in young smokers. Our findings suggested that alterations of alpha coherence may provide support to the earlier nicotine-dependence-related research findings, which may help us to understand the neuropathology of inhibitory control in young smokers.

Misconfigured striatal connectivity profiles in smokers

Dysregulation of frontal cortical inputs to the striatum is foundational in the neural basis of substance use disorder (SUD). Neuroanatomical and electrophysiological data increasingly show that striatal nodes receive appreciable input from numerous cortical areas, and that the combinational properties of these multivariate "connectivity profiles" play a predominant role in shaping striatal activity and function. Yet, how abnormal configuration of striatal connectivity profiles might contribute to SUD is unknown. Here, we implemented a novel "connectivity profile analysis" (CPA) approach using resting-state functional connectivity data to facilitate detection of different types of connectivity profile "misconfiguration" that may reflect distinct forms of aberrant circuit plasticity in SUD. We examined 46 nicotine-dependent smokers and 33 non-smokers and showed that both dorsal striatum (DS) and ventral striatum (VS) connectivity profiles with frontal cortex were misconfigured in smokers-but in doubly distinct fashions. DS misconfigurations were stable across sated and acute abstinent states (indicative of a "trait" circuit adaptation) whereas VS misconfigurations emerged only during acute abstinence (indicative of a "state" circuit adaptation). Moreover, DS misconfigurations involved abnormal connection strength rank order arrangement, whereas VS misconfigurations involved abnormal aggregate strength. We found that caudal ventral putamen in smokers uniquely displayed multiple types of connectivity profile misconfiguration, whose interactive magnitude was linked to dependence severity, and that VS misconfiguration magnitude correlated positively with withdrawal severity during acute abstinence. Findings underscore the potential for approaches that more aptly model the neurobiological composition of corticostriatal circuits to yield deeper insights into the neural basis of SUD.

A review of functional brain differences predicting relapse in substance use disorder: Actionable targets for new methods of noninvasive brain stimulation

Neuroimaging studies have identified a variety of brain regions whose activity predicts substance use (i.e., relapse) in patients with substance use disorder (SUD), suggesting that malfunctioning brain networks may exacerbate relapse. However, this knowledge has not yet led to a marked improvement in treatment outcomes. Noninvasive brain stimulation (NIBS) has shown some potential for treating SUDs, and a new generation of NIBS technologies offers the possibility of selectively altering activity in both superficial and deep brain structures implicated in SUDs. The goal of the current review was to identify deeper brain structures involved in relapse to SUD and give an account of innovative methods of NIBS that might be used to target them. Included studies measured fMRI in currently abstinent SUD patients and tracked treatment outcomes, and fMRI results were organized with the framework of the Addictions Neuroclinical Assessment (ANA). Four brain structures were consistently implicated: the anterior and posterior cingulate cortices, ventral striatum and insula. These four deeper brain structures may be appropriate future targets for the treatment of SUD using these innovative NIBS technologies.

Mini-review: When neurostimulation joins cognitive-behavioral therapy. On the need of combining evidence-based treatments for addiction disorders

Substance and behavioral addiction is a global health problem related to cognitive functioning and emotional responses like top-down control and craving. The present review discusses the role of non-invasive brain stimulation (NIBS) and cognitive-behavioral therapy (CBT) as evidence-based treatments for addiction disorders. The discussion spans between several evidence for both therapies, also considering the difference and heterogeneity among clinical protocols. Nowadays, literature is consistent in indicating the neurostimulation of the prefrontal cortex as effective for different kinds of addiction, corroborating the evidence that they rely on a common network in the brain. Likewise, within the CBT studies it is possible to observe a wide range of interventions that are overall effective in regulating the executive functions associated with addiction disorders. Nevertheless, the integration of NIBS and CBT in addictions has been scarcely considered in literature so far. For this reason, the present article is meant to foster empirical research in this field by highlighting the findings supporting these evidence-based interventions, both as stand-alone and integrated treatments. To this aim, psychological and neurophysiological mechanisms of NIBS and CBT in addictions are reviewed, and the rationale of their integration discussed. In particular, as evidence suggest these treatments affect top-down and bottom-up processes in different ways, with NIBS reducing craving and CBT boosting motivation and coping, we suggest their combination might better target the different components of addiction to promote abstinence.

Abnormal resting-state EEG power and impaired inhibition control in young smokers

Exposure to nicotine during adolescence may cause neurophysiological changes and increase the risks of developing nicotine dependence; it can even lead to lifelong smoking. The intake of nicotine may also lead to abnormal patterns of oscillatory brain activity and inhibition control deficits. However, little is known about the specific relationship between oscillatory brain activity during the resting state and inhibition control capacity in young smokers. In the present study, we acquired resting-state electroencephalography (EEG) data from thirty-four young smokers and 39 age-matched non-smoking controls. Inhibition control performance was measured by a Go/NoGo task. Compared with non-smoking controls, we detected reduced low-frequency delta band activity in the frontal, central and posterior cortices of young smokers. Furthermore, young smokers committed more errors in response to infrequent NoGo trials. Notably, we demonstrated that delta absolute power in the frontal region was negatively correlated with NoGo errors and that alpha power in the central region was positively correlated with NoGo errors in non-smoking controls but not in young smokers. These findings may suggest that these inhibitory control processes were associated with alterations in oscillatory brain activity during the resting state. Our findings suggest that alterations of power spectra in delta bands may act as a useful biomarker of inhibitory control performance and provide a scientific basis for the diagnosis and treatment of nicotine addiction in adolescents.

Translational Research in Nicotine Addiction

While commendable strides have been made in reducing smoking initiation and improving smoking cessation rates, current available smoking cessation treatment options are still only mildly efficacious and show substantial interindividual variability in their therapeutic responses. Therefore, the primary goal of preclinical research has been to further the understanding of the neural substrates and genetic influences involved in nicotine's effects and reassess potential drug targets. Pronounced advances have been made by investing in new translational approaches and placing more emphasis on bridging the gap between human and rodent models of dependence. Functional neuroimaging studies have identified key brain structures involved with nicotine-dependence phenotypes such as craving, impulsivity, withdrawal symptoms, and smoking cessation outcomes. Following up with these findings, rodent-modeling techniques have made it possible to dissect the neural circuits involved in these motivated behaviors and ascertain mechanisms underlying nicotine's interactive effects on brain structure and function. Likewise, translational studies investigating single-nucleotide polymorphisms (SNPs) within the cholinergic, dopaminergic, and opioid systems have found high levels of involvement of these neurotransmitter systems in regulating the reinforcing aspects of nicotine in both humans and mouse models. These findings and coordinated efforts between human and rodent studies pave the way for future work determining gene by drug interactions and tailoring treatment options to each individual smoker.

Altered functional connectivity of the dorsal attention network among problematic social network users

Many smartphone users spend excessive amounts of time online and cannot control their behavior, and the addictive overuse of social-networking services has been shown to be associated with diminished executive control. Attentional control is a cognitive process crucial to exerting executive functions. The purpose of this study was to investigate functional connectivity (FC) characteristics of attention networks in problematic social-network users. We performed seed-based resting-state FC analyses for 29 males and 10 females with excessive social network use and 32 healthy males and 17 healthy females. The right intraparietal sulcus and frontal eye fields were considered seeds of the dorsal attention network (DAN), and the right temporoparietal junction and ventral frontal cortex were considered seeds of the ventral attention network (VAN). Clinical characteristics predictive of FC findings in problematic social network users were identified through hierarchical multiple regression analysis. In FC analysis with DAN seeds, FC between the right intraparietal sulcus and the right middle occipital gyrus was stronger in problematic social network users than in controls, and FC between the right frontal eye field and the right dorsolateral prefrontal cortex was weaker than that in controls. There was no significant difference between the groups in FC analysis with VAN seeds. Hierarchical regression analyses showed that usage times on social networking platforms significantly predicted the negative effects on the strength of FC between the intraparietal sulcus and the dorsolateral prefrontal cortex. These findings indicated that problematic social network use reflects changes in the neural circuits underlying attentional control. Weaking of prefrontal control for attention networks would have a significant impact on failure to control one's time spent on social networks.

Distinct patterns of prefrontal cortical disengagement during inhibitory control in addiction: A meta-analysis based on population characteristics

Prefrontal cortical dysfunctions underlying inhibitory control deficits in addiction are complex and likely dependent on population characteristics. Here, we conducted a meta-analysis to examine alterations in brain activations during response inhibition in addicted individuals. We characterized imaging findings based on substance use status, diagnosis, substance classes, and task performance. Results revealed in those with active drug addiction hypoactivation of the left dorsal anterior cingulate cortex (dACC) and right middle frontal gyrus (MFG), compared with healthy controls. Weakening of the dACC and MFG activations was particularly pronounced in nicotine users, respectively. Impaired task performance was also associated with diminished MFG activation. In contrast, abstinent users did not exhibit any significant differences compared with healthy controls. Those with behavioral addictions were characterized by higher midcingulate cortical activation. Thus, the neural disengagement during response inhibition in active drug addiction was limited to a small number of prefrontal cortical regions and dependent on population characteristics. Finally, the evidence for potential normalization of hypofrontality following substance use cessation highlights the benefits of abstinence in restoring cerebral functions.

Altered neural activities during response inhibition in adults with addiction: a voxel-wise meta-analysis

BACKGROUND

Previous literature has extensively investigated the brain activity during response inhibition in adults with addiction. Inconsistent results including both hyper- and hypo-activities in the fronto-parietal network (FPN) and the ventral attention network (VAN) have been found in adults with addictions, compared with healthy controls (HCs).

METHODS

Voxel-wise meta-analyses of abnormal task-evoked regional activity were conducted for adults with substance dependence (SD) and behavioral addiction during response inhibition tasks to solve previous inconsistencies. Twenty-three functional magnetic resonance imaging studies including 479 substance users, 38 individuals with behavioral addiction and 494 HCs were identified.

RESULTS

Compared with HCs, all addictions showed hypo-activities in regions within FPN (inferior frontal gyrus and supramarginal gyrus) and VAN (inferior frontal gyrus, middle temporal gyrus, temporal pole and insula), and hyper-activities in the cerebellum during response inhibition. SD subgroup showed almost the same activity patterns, with an additional hypoactivation of the precentral gyrus, compared with HCs. Stronger activation of the cerebellum was associated with longer addiction duration for adults with SD. We could not conduct meta-analytic investigations into the behavioral addiction subgroup due to the small number of datasets.

CONCLUSION

This meta-analysis revealed altered activation of FPN, VAN and the cerebellum in adults with addiction during response inhibition tasks using non-addiction-related stimuli. Although FPN and VAN showed lower activity, the cerebellum exhibited stronger activity. These results may help to understand the neural pathology of response inhibition in addiction.

A double-blind randomized clinical trial of high frequency rTMS over the DLPFC on nicotine dependence, anxiety and depression

High frequency repetitive transcranial magnetic stimulation (HF-rTMS) over the left dorsolateral prefrontal cortex (L-DLPFC) is a widely applied treatment protocol for chronic smoking and major depressive disorder. However, no previous study has measured the effects of rTMS on both nicotine consumption and anxiety/depression in the same volunteers despite the relationship between them. The aim of this work was to evaluate the efficacy of 10 daily sessions of HF-rTMS over the L-DLPFC in chronic cigarette smokers' addiction and investigate the possible beneficial effects of this treatment procedure on symptoms of depression and anxiety in the same subjects. The study included 40 treatment-seeking nicotine-dependent cigarette smokers. Onset/duration of smoking, number of cigarettes/day, Fagerstrom Test of Nicotine Dependence (FTND), Tobacco Craving Questionnaire-Short Form (TCQ-SF), Hamilton depression and anxiety scales (HAM-D and HAM-A) were recorded. Participants were randomly assigned to the active or the sham treatment group. Those in the active group received 10 trains of 20 Hz stimulation, at 80% of the resting motor threshold (rMT) for 10 consecutive working days over L-DLPFC. Participants were reassessed immediately after treatment, and then 3 months later using all rating scales. There were no differences between active and sham groups at baseline. The cigarette consumption/day, and scores on FTND, and TCQ decreased significantly in both groups (p = 0.0001 for each) immediately after treatment. However, improvement persisted to 3 months in the active group but not in the sham group. Moreover, there was a significant reduction in HAM-D and HAM-A scores immediately after treatment in the active but not the sham group. Subjects with a longer history of smoking had a lower percent improvement in FTND (p = 0.005). Our findings revealed that HF-rTMS over L-DLPCF for 10 days reduced cigarette consumption, craving, dependence, and improved associated symptoms of anxiety and depression.ClinicalTrials.gov Identifier: NCT03264755 registered at 29/08/2017.

Cognitive Training: Associations and Implications for Weight Management and Translational Research

Behavioral weight loss programs combining energy restriction and increased physical activity (PA) are generally successful in producing clinically significant weight loss (≥5%) over 3-6 mos. However, weight maintenance (≥ 2 yrs.) continues to be problematic, due in part to an inability of individuals to continue adherence to diet and PA recommendations. It is hypothesized that neurocognitive processes, specifically executive functions (EFs, i.e., inhibition, working memory, mental flexibility), underlie self-regulation, self-efficacy, and are essential for the adoption and maintenance of health behaviors. Behavioral weight loss programs generally attempt to improve self-regulation; however, these skills are difficult to implement long-term. Strengthening EFs through cognitive training may improve weight maintenance by improving self-efficacy and self-regulation, resulting in improved program attendance and improved adherence to dietary and PA recommendations. Although randomized trials have not been conducted to specifically evaluate this hypothesis, results from the available literature suggest the potential for cognitive training to improve weight maintenance.

Associations Between Smoking Abstinence, Inhibitory Control, and Smoking Behavior: An fMRI Study

Nicotine addiction is associated with dysregulated inhibitory control (IC), mediated by corticothalamic circuitry including the right inferior frontal gyrus (rIFG). Among sated smokers, worse IC task performance and greater IC-related rIFG activity have been shown to be associated with greater relapse vulnerability. The present study investigated the effects of smoking abstinence on associations between IC task performance, rIFG activation, and smoking behavior. Smokers (N = 26, 15 female) completed an IC task (Go/Go/No-go) during fMRI scanning followed by a laboratory-based smoking relapse analog task (SRT) on two visits: once when sated and once following 24 h of smoking abstinence. During the SRT, smokers were provided with monetary rewards for incrementally delaying smoking. A significant main effect of No-go accuracy on latency to smoke during the SRT was observed when collapsing across smoking states (abstinent vs. sated). Similarly, a significant main effect of IC-related activation in rIFG on SRT performance was observed across states. The main effect of state, however, was non-significant in both of these models. Furthermore, the interaction between smoking state and No-go accuracy on SRT performance was non-significant, indicating a similar relationship between IC and lapse vulnerability under both sated and abstinent conditions. The state X rIFG activation interaction on SRT performance was likewise non-significant. Post-hoc whole brain analyses indicated that abstinence resulted in greater IC-related activity in the right middle frontal gyrus (MFG) and insula. Activation during IC in these regions was significantly associated with decreased No-go accuracy. Moreover, greater abstinence induced activity in right MFG during IC was associated with smoking sooner on the SRT. These findings are bolstered by the extant literature on the effects of nicotine on executive function and also contribute novel insights on how individual differences in behavioral and neuroimaging measures of IC may influence relapse propensity independent of smoking state.

Effectiveness of Interventions Based on Yogic Breathing Practices (IB-YBP) on Substance Use Disorders-A Systematic Review of the Randomized Control Trials and Quasi-Experimental Trials

Interventions based on Yogic Breathing Practices (IB-YBP) have shown promising results for substance use disorders (SUD). Research in this area is methodologically heterogeneous and only a few, but restricted, systematic reviews are available. The current systematic review aims to assess the effectiveness of IB-YBP for SUD. Materials and Methods: PubMed, Cochrane's Library, EBSCO-Medline, and Google Scholar databases were searched for the randomized- (RCTs) and quasi-randomized trials. Research involving participants with SUD, of either gender or any age, assessing the effectiveness of the IB-YBP either as a standalone intervention or as an adjuvant to standard treatment versus standard pharmacological/non-pharmacological treatment or no-intervention control were included. Studies having participants with co-morbid psychiatric illness and interventions not having IB-YBP as the predominant component were excluded. Results: The initial literature search yielded 396 articles and upon screening, only 14 studies were found eligible for this review. Most studies have researched IB-YBP as an adjunct to the standard treatment for SUD. Evidence for the effectiveness of IB-YBP is mostly available for tobacco and opioid use disorders, though only for short-term outcomes; however, literature is scarce for alcohol- and cocaine-use disorders. This review documented the effectiveness of the IB-YBP for substance use-related outcome parameters such as abstinence, quality of life (QoL), mood, craving, and withdrawal symptoms. Conclusion: IB-YBP may be an effective adjuvant to standard treatment for various SUD. However, more research is required to compare its effectiveness with standard treatment, and assessing its long-term efficacy, for it to be strongly recommended as a treatment strategy.

Changes in Cigarette Consumption With Reduced Nicotine Content Cigarettes Among Smokers With Psychiatric Conditions or Socioeconomic Disadvantage: 3 Randomized Clinical Trials

IMPORTANCE

This study is part of a programmatic effort evaluating the effects of reducing nicotine content of cigarettes to minimally addictive levels.

OBJECTIVE

To examine whether very low-nicotine-content (VLNC) cigarettes decrease smoking rates and dependence severity among smokers with psychiatric disorders or socioeconomic disadvantage.

DESIGN, SETTING, AND PARTICIPANTS

These 3 randomized clinical trials were performed at the University of Vermont, Brown University, and Johns Hopkins University between October 2016 and September 2019. Participants received 12 weeks of exposure to study cigarettes with nicotine content ranging from levels representative of commercial cigarettes (15.8 mg nicotine/g tobacco) to less than a hypothesized addiction threshold (2.4 mg/g and 0.4 mg/g). Daily smokers from 3 at-risk populations participated: individuals with affective disorders, exemplifying smokers with mental illness; individuals with opioid use disorder, exemplifying smokers with substance use disorders; and women with high school educations or less, exemplifying smokers with socioeconomic disadvantage. Data were analyzed from September 2019 to July 2020.

INTERVENTIONS

Random assignment to 1 of 3 study cigarettes provided weekly at no cost for 12 weeks.

MAIN OUTCOMES AND MEASURES

The primary outcome was between-group differences in mean total cigarettes smoked daily (CPD) during week 12; secondary outcomes included CPD for study and nonstudy cigarettes and dependence severity across weeks analyzed using analysis of covariance, random coefficients growth modeling, or repeated measures analysis of variance.

RESULTS

A total of 775 participants were included (mean [SD] age, 35.59 [11.05] years; 551 [71.10%] women [owing to 1 population being exclusively women]); participants smoked a mean (SD) of 17.79 (9.18) CPD at study intake. A total of 286 participants were randomized to 0.4 mg/g, 235 participants were randomized to 2.4 mg/g, and 254 participants were randomized to 15.8 mg/g. Participants randomized to VLNC cigarettes had decreased mean [SEM] total CPD during week 12 across populations (Cohen d = 0.61; P < .001). At week 12, mean (SEM) CPD decreased to 17.96 (0.98) CPD in the 0.4 mg/g group and to 19.53 (1.07) CPD in the 2.4 mg/g group, both of which were significantly different from the 15.8 mg/g group (25.08 [1.08] CPD at week 12) but not each other (0.4 mg/g adjusted mean difference: -7.54 [95%CI, -9.51 to -5.57]; 2.4 mg/g adjusted mean difference: -5.34 [95% CI, 7.41 to -3.26]). Several secondary outcomes differed across populations randomized to VLNCs, including mean total CPD across weeks, with linear trends lower in participants receiving 0.4 mg/g (-0.28 [95%CI, -0.39 to -0.18]; P < .001) and 2.4 mg/g (-0.13 [95%CI, -0.25 to -0.01]; P < .001) doses compared with those receiving the 15.8 mg/g dose (0.30 [95% CI, 0.19 to 0.41]). Fagerström Test of Nicotine Dependence mean total scores were significantly lower in participants who received VLNCs (Cohen d = 0.12; P < .001), with those who received the 0.4 mg/g dose (mean [SD] score, 3.99 [0.06]; P < .001 vs 15.8 mg/g) or 2.4 mg/g dose (mean [SD] score, 4.07 [0.06]; P = .01 vs 15.8 mg/g) differing from those who received the 15.8 mg/g dose (mean [SD] score, 4.31 [0.06]) but not from each other.

CONCLUSIONS AND RELEVANCE

These findings demonstrate that decreasing the nicotine content of cigarettes to very low levels reduced smoking rate and nicotine-dependence severity in these high-risk populations, effects that may facilitate successful cessation.

TRIAL REGISTRATION

ClinicalTrials.gov Identifiers: NCT02232737, NCT02250664, NCT02250534.

A neurobiological correlate of stress-induced nicotine-seeking behavior among cigarette smokers

Stress is known to influence smoking relapse. Experimental studies indicate that acute stress increases nicotine-seeking behavior, yet neurobiological mechanisms remain poorly understood. Herein, we investigated disrupted excitatory neural activity in the dorsolateral prefrontal cortex (dlPFC) as a mechanism of stress-induced nicotine-seeking behavior. Non-treatment-seeking cigarette smokers were screened for psychiatric, medical, and neuroimaging contraindications. Using a double-blind, placebo-controlled, randomized crossover design, participants (N = 21) completed two oral-dosing sessions: stress (yohimbine 54 mg + hydrocortisone 10 mg) vs placebo (lactose 54 mg + lactose 10 mg). During each experimental session, working memory proficiency, dlPFC excitatory neural activity, nicotine-seeking behavior, and subjective effects were measured. dlPFC excitatory neural activity was quantified via glutamate modulation during working memory performance using functional proton magnetic resonance spectroscopy. Nicotine-seeking behavior was assayed using a cigarette puffs vs money choice progressive ratio task. Results indicated that yohimbine + hydrocortisone evoked a sustained physiological stress response (elevated heart rate, blood pressure, saliva cortisol, and saliva α-amylase levels; ps < .05). Relative to placebo levels, acute stress increased nicotine-seeking behavior (ps < .05), disrupted dlPFC glutamate modulation (p = .025), and impaired dlPFC function (working memory proficiency; ps < .05). The stress-induced increase in nicotine-seeking behavior was linearly related to the stress-induced disruption of dlPFC glutamate modulation (R²  = 0.24-0.37; ps < .05). These findings suggest that disrupted dlPFC excitatory neural activity is a neurobiological correlate of acute stress-induced nicotine-seeking behavior. These findings further emphasize the central role of the dlPFC in regulating drug-seeking behavior. Future studies are needed to evaluate interventions to improve dlPFC resilience to acute stress effects, including neurostimulation, working memory training, and "anti-stress" medications.

A temporal chronnectomic framework: Cigarette smoking preserved the prefrontal dysfunction in schizophrenia

The widespread cigarette smoking behavior in schizophrenia is generally attributed to its alleviation of patients' symptomatology by the self-medication hypothesis. The prefrontal cortex (PFC), which predominantly supports orchestrating thoughts and actions, might underlie the biological underpinnings of smoking behavior in schizophrenia. However, few studies have focused on the impact of smoking on the prefrontal function in schizophrenia. This study assumed that smoking-related alterations on the prefrontal dynamics of information integration (chronnectome) were different between healthy control (HC) and schizophrenia patient (SP). We recruited SP smokers (N = 22)/nonsmokers (N = 27) and HC smokers (N = 22)/nonsmokers (N = 21) who underwent resting-state functional magnetic resonance imaging (rsfMRI) with a total of 240 volumes (lasting for 480 s). We employed a chronnectomic density analysis on the rsfMRI signal by using a sliding-window method. We examined the interaction effect between smoking status and diagnosis utilizing two-way analysis of covariance under permutation test. Whereas disease-related reduced effects were found on the bilateral dorsolateral PFC chronnectomic density, no smoking effect was observed. As regards interaction effect, a smoking-related reduced effect was found on the right dorsolateral PFC chronnectomic density in HC, while a smoking-related increased effect was observed in SP. Nevertheless, post-hoc analysis revealed significant group difference between SP smokers and HC nonsmokers. Therefore, these results indicated a smoking-related preservation effect on disrupted prefrontal dynamics in schizophrenia that cannot restore it to normal levels. The novel findings yield a prefrontal-based chronnectome framework to elaborate upon the self-medication hypothesis in schizophrenia.

Multimodal Neuroimaging Differences in Nicotine Abstinent Smokers Versus Satiated Smokers

INTRODUCTION

Research on cigarette smokers suggests cognitive and behavioral impairments. However, much remains unclear how the functional neurobiology of smokers is influenced by nicotine state. Therefore, we sought to determine which state, be it acute nicotine abstinence or satiety, would yield the most robust differences compared with nonsmokers when assessing neurobiological markers of nicotine dependence.

METHODS

Smokers (N = 15) and sociodemographically matched nonsmokers (N = 15) were scanned twice using a repeated-measures design. Smokers were scanned after a 24-hour nicotine abstinence and immediately after smoking their usual brand cigarette. The neuroimaging battery included a stop-signal task of response inhibition and pseudocontinuous arterial spin labeling to measure cerebral blood flow (CBF). Whole-brain voxel-wise analyses of covariance were carried out on stop success and stop fail Stop-Signal Task contrasts and CBF maps to assess differences among nonsmokers, abstinent smokers, and satiated smokers. Cluster correction was performed using AFNI's 3dClustSim to achieve a significance of p < .05.

RESULTS

Smokers exhibited higher brain activation in bilateral inferior frontal gyrus, a brain region known to be involved in inhibitory control, during successful response inhibitions relative to nonsmokers. This effect was significantly higher during nicotine abstinence relative to satiety. Smokers also exhibited lower CBF in the bilateral inferior frontal gyrus than nonsmokers. These hypoperfusions were not different between abstinence and satiety.

CONCLUSIONS

These findings converge on alterations in smokers in prefrontal circuits known to be critical for inhibitory control. These effects are present, even when smokers are satiated, but the neural activity required to achieve performance equal to controls is increased when smokers are in acute abstinence.

IMPLICATIONS

Our multimodal neuroimaging study gives neurobiological insights into the cognitive demands of maintaining abstinence and suggests targets for assessing the efficacy of therapeutic interventions.

Nicotine dependence (trait) and acute nicotinic stimulation (state) modulate attention but not inhibitory control: converging fMRI evidence from Go-Nogo and Flanker tasks

Cognitive deficits during nicotine withdrawal may contribute to smoking relapse. However, interacting effects of chronic nicotine dependence and acute nicotine withdrawal on cognitive control are poorly understood. Here we examine the effects of nicotine dependence (trait; smokers (n = 24) vs. non-smoking controls; n = 20) and acute nicotinic stimulation (state; administration of nicotine and varenicline, two FDA-approved smoking cessation aids, during abstinence), on two well-established tests of inhibitory control, the Go-Nogo task and the Flanker task, during fMRI scanning. We compared performance and neural responses between these four pharmacological manipulations in a double-blind, placebo-controlled crossover design. As expected, performance in both tasks was modulated by nicotine dependence, abstinence, and pharmacological manipulation. However, effects were driven entirely by conditions that required less inhibitory control. When demand for inhibitory control was high, abstinent smokers showed no deficits. By contrast, acutely abstinent smokers showed performance deficits in easier conditions and missed more trials. Go-Nogo fMRI results showed decreased inhibition-related neural activity in right anterior insula and right putamen in smokers and decreased dorsal anterior cingulate cortex activity on nicotine across groups. No effects were found on inhibition-related activity during the Flanker task or on error-related activity in either task. Given robust nicotinic effects on physiology and behavioral deficits in attention, we are confident that pharmacological manipulations were effective. Thus findings fit a recent proposal that abstinent smokers show decreased ability to divert cognitive resources at low or intermediate cognitive demand, while performance at high cognitive demand remains relatively unaffected, suggesting a primary attentional deficit during acute abstinence.

Double jeopardy: Comorbid obesity and cigarette smoking are linked to neurobiological alterations in inhibitory control during smoking cue exposure

Obesity and cigarette smoking are two of the leading preventable causes of death in the United States. Research suggests that overlapping pathophysiology may contribute to obesity and nicotine use disorder (NUD), yet no studies have investigated the effect of obesity on neural response to reward stimuli in NUD. This study used arterial spin-labeled perfusion functional magnetic resonance imaging (fMRI) to examine neural responses during exposure to smoking versus nonsmoking cues in 79 treatment-seeking participants with NUD, 26 with normal weight, 28 with overweight, and 25 with obesity. Given that deficits in behavioral inhibitory control have been associated with both obesity and NUD, participants completed an affect-congruent Go/NoGo task to assess the effect of body mass index (BMI) on this construct in NUD. Analyses revealed that BMI was negatively associated with activation in the right dorsolateral prefrontal cortex (dlPFC) in response to smoking cues, with significantly reduced response in smokers with overweight and smokers with obesity compared with normal-weight smokers. In addition, greater commission errors on the Go/NoGo task were correlated with reduced neural response to smoking cues in the right dlPFC only among those with obesity. Together, these findings provide evidence that obesity in treatment-seeking NUDs is related to neurobiological alterations in inhibitory control over cue-potentiated behaviors, suggesting that smoking cessation may be more difficult in individuals with comorbid NUD and obesity than in those without, requiring treatment strategies tailored to meet their unique needs.

Dissociable Effects of Theta-Burst Repeated Transcranial Magnetic Stimulation to the Inferior Frontal Gyrus on Inhibitory Control in Nicotine Addiction

Nicotine addiction, like other substance use disorders (SUD's), is associated with deficits in prefrontal mediated inhibitory control. The strength of inhibitory control task-based functional connectivity (tbFC) between the right inferior frontal gyrus (r.IFG) and thalamus (corticothalamic circuit) mediates the association between successful inhibition and smoking relapse vulnerability. However, the potential efficacy of theta burst stimulation (TBS) to the r.IFG, a treatment known to alter clinical symptoms among neuropsychiatric patients, has not been reported in a SUD population. This study utilized fMRI guided neuronavigation to examine the effects of TBS on inhibitory control among nicotine dependent individuals. Participants (N=12) were scanned while performing an inhibitory control task known to elicit inhibition-related activity in the r.IFG. Using a randomized, counterbalanced cross-over design, participants then received TBS over two visits: excitatory (iTBS) on one visit and inhibitory (cTBS) TBS on the other visit. The effects of each TBS condition on subsequent inhibitory control task performance were examined. A significant condition x time interaction was identified on trials requiring inhibitory control (F (1,10) = 7.27, p = .022, D = 1.63). iTBS improved inhibitory control, whereas cTBS impaired inhibitory control. Brain stimulation did not influence performance in control conditions including novelty detection and response execution. This is the first study to demonstrate that non-invasive neural stimulation using iTBS to the r.IFG enhances baseline inhibitory control among individuals with a SUD. Further research is needed to directly examine the potential parametric effects of TBS on corticothalamic tbFC in individuals with a SUD.

Neuroimaging reward, craving, learning, and cognitive control in substance use disorders: review and implications for treatment

Substance use disorder is a leading causes of preventable disease and mortality. Drugs of abuse cause molecular and cellular changes in specific brain regions and these neuroplastic changes are thought to play a role in the transition to uncontrolled drug use. Neuroimaging has identified neural substrates associated with problematic substance use and may offer clues to reduce its burden on the patient and society. Here, we provide a narrative review of neuroimaging studies that have examined the structures and circuits associated with reward, cues and craving, learning, and cognitive control in substance use disorders. Most studies use advanced MRI or positron emission tomography (PET). Many studies have focused on the dopamine neurons of the ventral tegmental area, and the regions where these neurons terminate, such as the striatum and prefrontal cortex. Decreases in dopamine receptors and transmission have been found in chronic users of drugs, alcohol, and nicotine. Recent studies also show evidence of differences in structure and function in substance users relative to controls in brain regions involved in salience evaluation, such as the insula and anterior cingulate cortex. Balancing between reward-related bottom-up and cognitive-control-related top-down processes is discussed in the context of neuromodulation as a potential treatment. Finally, some of the challenges for understanding substance use disorder using neuroimaging methods are discussed.

Naltrexone differentially modulates the neural correlates of motor impulse control in abstinent alcohol-dependent and polysubstance-dependent individuals

Identifying key neural substrates in addiction disorders for targeted drug development remains a major challenge for clinical neuroscience. One emerging target is the opioid system, where substance-dependent populations demonstrate prefrontal opioid dysregulation that predicts impulsivity and relapse. This may suggest that disturbances to the prefrontal opioid system could confer a risk for relapse in addiction due to weakened 'top-down' control over impulsive behaviour. Naltrexone is currently licensed for alcohol dependence and is also used clinically for impulse control disorders. Using a go/no-go (GNG) task, we examined the effects of acute naltrexone on the neural correlates of successful motor impulse control in abstinent alcoholics (AUD), abstinent polysubstance-dependent (poly-SUD) individuals and controls during a randomised double blind placebo controlled fMRI study. In the absence of any differences on GNG task performance, the AUD group showed a significantly greater BOLD response compared to the control group in lateral and medial prefrontal regions during both placebo and naltrexone treatments; effects that were positively correlated with alcohol abstinence. There was also a dissociation in the positive modulating effects of naltrexone in the orbitofrontal cortex (OFC) and anterior insula cortex (AIC) of the AUD and poly-SUD groups respectively. Self-reported trait impulsivity in the poly-SUD group also predicted the effect of naltrexone in the AIC. These results suggest that acute naltrexone differentially amplifies neural responses within two distinct regions of a salience network during successful motor impulse control in abstinent AUD and poly-SUD groups, which are predicted by trait impulsivity in the poly-SUD group.

The Attentional Bias in Current and Former Smokers

Attentional bias has been defined as the propensity of a person to allocate selective attention automatically to salient cues (Field and Powell, 2007). In the case of smoking, this bias implies that smokers are implicitly attracted by smoking-related stimuli, which produce behavioral, memory, and emotional effects (Volkow et al., 2006; Giardini et al., 2009). In more detail, scientific evidence pointed out that smoking is strongly supported by attentional bias that activates craving and urgency to smoke a cigarette. However, poor and conflicting data are available regarding the role of this cognitive bias on former smokers. The main aim of this study is to explore the occurrence of the attentional bias on of both current and former smokers, also with the aim to identify associations with behavioral, psychological and cognitive characteristic of participants. We collected data on 245 current, volunteers (male 50.6%; female 49.4%) aged 54.81 (SD = 14.352, range = 18–63), divided in current smokers (98), former smokers (102) and non-smokers (45). A combination of neuropsychology tests (Emotional Smoke Stroop Task and Go/no-Go task), and standardized questionnaires [Behavioral Inhibition System-Behavioral Approach System (BIS-BAS), Fagerström Test for Nicotine Dependence (FTND), Barratt Impulsiveness Scale, Motivational questionnaire] were used to assess the attentional bias, psychological variables, and smoking-related characteristics. Responses at the Emotional Smoke Stroop task revealed that current and former smokers are actually slower than non-smokers are when facing smoking cues, while performances at other Stroop conditions and at the Go/no-Go task are not statistically different. These results confirmed the occurrence of the attentional bias in current smokers, and above all points out that the same effect is present in former smokers. We found only small and selective correlations between attentional bias and psychological variables (e.g., impulsiveness and inhibition). In particular, impulsivity is not directly associated with the AB intensity. Also, smoking characteristics (e.g., years of smoking and dependence level) and the length of the period of abstinence do not seem to modulate implicit cognition of smoking cue. Our data support the idea that the attentional bias may be considered relevant in sustaining smoking and favoring relapse.

The insula in nicotine use disorder: Functional neuroimaging and implications for neuromodulation

Insula dysfunction contributes to nicotine use disorders. Yet, much remains unknown about how insular functions promote nicotine use. We review current models of brain networks in smoking and propose an extension to those models that emphasizes the role of the insula in craving. During acute withdrawal, the insula provides the sensation of craving to the cerebrum and is thought to negotiate craving sensations with cognitive control to guide behavior - either to smoke or abstain. Recent studies have shown that insula processing is saturable, such that different insular functions compete for limited resources. We propose that this saturability explains how craving during withdrawal can overload insular processing to the exclusion of other functions, such as saliency and network homeostasis. A novel signal flow model illustrates how limited insular capacity leads to breakdown of normal function. Finally, we discuss suitability of insula as a neuromodulation target to promote cessation. Given the limited efficacy of standard-of-care treatments for nicotine use disorder, insular neuromodulation offers an innovative, potentially therapeutic target for improving smoking cessation.

Impaired learning from punishment of errors in smokers: Differences in dorsolateral prefrontal cortex and sensorimotor cortex blood-oxygen-level dependent responses

Cigarette smokers have shown hypersensitivity to reward and hyposensitivity to punishment, along with impairments in learning from errors. The underlying neural mechanism for this failure to adapt performance following an error, particularly when receiving negative feedback, are unclear. Smokers were hypothesized to have poorer error-learning following monetary punishment, associated with hypoactivation in the insula, dorsal anterior cingulate, and hippocampal cortical regions. Twenty-three smokers (8 females, mean age = 25.48, SD = 4.46) and twenty-three healthy controls (13 females, mean age = 24.83, SD = 5.99) were administered an associative learning task, providing monetary reward and punishment for recall performance, during fMRI data collection. Compared with controls, smokers had a lower error-correction rate and were less sensitive to punishment magnitude. Hyperactivity during recall was independent of future error correction, but smokers' successful re-encoding appeared related to higher dorsolateral prefrontal cortex activity while controls had equivalent activation for corrected and repeated errors. While controls showed higher deactivation of the sensorimotor cortex during high punishment, smokers showed higher deactivation during low punishment. The present results support smokers having poorer learning from errors and decreased attentional control associated with hyperactivity in the dorsolateral prefrontal cortex. Additionally, smokers exhibited decreased punishment sensitivity that appeared to limit their ability to adapt learning in the face of repeated negative feedback.

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Smokers show impaired learning from punished errors.

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Controls are more sensitive to differences in punishment magnitude than smokers.

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Smokers show dorsolateral prefrontal cortex hyperactivity during recall.

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Smokers rely more on dorsolateral prefrontal cortex for correct re-encoding than controls.

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Smokers show aberrant sensorimotor cortex deactivation compared with controls.

Multivariate pattern analysis of the neural correlates of smoking cue attentional bias

The automatic capture of attention by drug cues, or attentional bias, is associated with craving and predicts future drug use. Despite its clinical significance, the neural bases of attentional bias to drug cues is not well understood. To address this gap, we undertook a neuroimaging investigation of the neural correlates of attentional bias towards smoking cues. Twenty-nine adults, including 14 active smokers and 15 non-smokers, completed a spatial cuing task during fMRI. A multivariate pattern analysis (MVPA) decoded the neural responses to the brief presentation of smoking versus neutral images. These data were correlated with behavioral measures of attentional bias, which included analyses targeting the neural correlates of response facilitation and cue-related task interference. We detected a set of brain-behavioral correlates that were similar across both smokers and non-smokers, indicating a role for stimuli salience in the absence of nicotine conditioning in smoking cue attentional bias. However, multiple smoking-related modifications to the neural correlates of attentional bias and its components were also identified. For example, regions demonstrating smoking-related differences in the neural correlates of attentional bias included the rostral anterior cingulate cortex and inferior frontal gyrus. Response facilitation effects of smoking were observed in the right orbitofrontal gyrus and bilateral middle temporal gyrus. Smoking-cue related task interference was related to smoking-related effects in the frontal eye fields. Our findings suggest that multiple cognitive, affective, and visual object recognition processes contribute to attentional bias towards smoking cues, and suggest multiple circuit modifications that may contribute to perpetuation of addiction.

Sex differences in tobacco smokers: Executive control network and frontostriatal connectivity

BACKGROUND

Women experience greater difficulty quitting smoking than men, which may be explained by sex differences in brain circuitry underlying cognitive control. Prior work has linked reduced interhemispheric executive control network (ECN) coupling with poor executive function, shorter time to relapse, and greater substance use. Lower structural connectivity between a key ECN hub, the dorsolateral prefrontal cortex (DLPFC), and the dorsal striatum (DS) also contributes to less efficient cognitive control recruitment, and reduced intrahemispheric connectivity between these regions has been associated with smoking relapse. Therefore, sex differences were probed by evaluating interhemispheric ECN and intrahemispheric DLPFC-DS connectivity. To assess the potential sex by nicotine interaction, a pilot sample of non-smokers was evaluated following acute nicotine and placebo administration.

METHODS

Thirty-five smokers (19 women) completed one resting state functional magnetic resonance imaging scan. Seventeen non-smokers (8 women) were scanned twice using a repeated measures design where they received 2 and 0 mg nicotine.

RESULTS

In smokers, women had less interhemispheric ECN and DLPFC-DS coupling than men. In non-smokers, there was a drug x sex interaction where women, relative to men, had weaker ECN coupling following nicotine but not placebo administration.

CONCLUSIONS

The current work indicates that nicotine-dependent women, versus men, have weaker connectivity in brain networks critically implicated in cognitive control. How these connectivity differences contribute to the behavioral aspects of smoking requires more testing. However, building on the literature, it is likely these deficits in functional connectivity contribute to the lower abstinence rates noted in women relative to men.

A Roadmap for Integrating Neuroscience Into Addiction Treatment: A Consensus of the Neuroscience Interest Group of the International Society of Addiction Medicine

Although there is general consensus that altered brain structure and function underpins addictive disorders, clinicians working in addiction treatment rarely incorporate neuroscience-informed approaches into their practice. We recently launched the Neuroscience Interest Group within the International Society of Addiction Medicine (ISAM-NIG) to promote initiatives to bridge this gap. This article summarizes the ISAM-NIG key priorities and strategies to achieve implementation of addiction neuroscience knowledge and tools for the assessment and treatment of substance use disorders. We cover two assessment areas: cognitive assessment and neuroimaging, and two interventional areas: cognitive training/remediation and neuromodulation, where we identify key challenges and proposed solutions. We reason that incorporating cognitive assessment into clinical settings requires the identification of constructs that predict meaningful clinical outcomes. Other requirements are the development of measures that are easily-administered, reliable, and ecologically-valid. Translation of neuroimaging techniques requires the development of diagnostic and prognostic biomarkers and testing the cost-effectiveness of these biomarkers in individualized prediction algorithms for relapse prevention and treatment selection. Integration of cognitive assessments with neuroimaging can provide multilevel targets including neural, cognitive, and behavioral outcomes for neuroscience-informed interventions. Application of neuroscience-informed interventions including cognitive training/remediation and neuromodulation requires clear pathways to design treatments based on multilevel targets, additional evidence from randomized trials and subsequent clinical implementation, including evaluation of cost-effectiveness. We propose to address these challenges by promoting international collaboration between researchers and clinicians, developing harmonized protocols and data management systems, and prioritizing multi-site research that focuses on improving clinical outcomes.

Neurobiological Considerations for Tobacco Use Disorder

PURPOSE OF REVIEW

Neurobiological studies of tobacco/nicotine use examining genetic, molecular, functional, and behavioral correlates have improved our understanding of nicotine/tobacco dependence and have informed treatment. Recent work extending previously established findings and reporting novel methodologies and discoveries in preclinical and human studies are reviewed.

RECENT FINDINGS

Recent work in preclinical models has focused on the differential roles of nicotinic receptor subtypes and nicotine's effects on neural systems beyond cortico-striatal dopaminergic pathways, and utilizing advanced methodologies such as pharmacogenetics, optogenetics and rodent fMRI to identify targets for treatment. Likewise, human neuroimaging studies have identified molecular and functional dynamic shifts associated with tobacco/nicotine use that further inform treatment.

SUMMARY

Nicotine/tobacco use is associated with widespread neural adaptations that are persistent and function to maintain addiction. The continued identification of genetic, molecular, neural, and behavioral endophenotypes related to nicotine/tobacco use, dependence, and addiction will facilitate the development and delivery of personalized treatment.

Male Smokers’ Behavioral and Brain Responses to Deviant Cigarette-Related Stimuli in a Two-Choice Oddball Paradigm

Abstract. Experimental studies on smoking and response-inhibition capacity have revealed inconsistent findings, which might be due to differences in sensitivity of the behavioral paradigms used. Here we aimed to replicate the impaired response inhibition in male smokers that was found in a previous study using a two-choice oddball task. This task enables the use of response times as index of inhibition capacity and equalizes the response requirement for the different trial types. In addition, we measured event-related brain potentials to explore the nature of the cognitive processes underlying the behavioral difference. Smokers (n = 19) and non-smokers (n = 19) were asked to make a different response to frequent standard stimuli (cigarette-unrelated pictures) than to infrequent deviant stimuli (cigarette-related pictures). Compared to non-smokers, smokers took a longer time to respond to deviant but not standard stimuli. In addition, smokers, but not non-smokers, displayed a smaller N2 amplitude to deviant than standard stimuli, and only the non-smokers showed larger P3 amplitudes to deviant compared to standard stimuli. Moreover, the response time (RT) measure was differentially correlated with N2 and P3 amplitudes in smokers and non-smokers. The joint results support the notion of deviant cognitive processes in smokers compared to non-smokers that are either directly or indirectly related to response-inhibition capacity.

Optimizing Electrode Montages of Transcranial Direct Current Stimulation for Attentional Bias Modification in Early Abstinent Methamphetamine Users

Introduction: Chronic use of most psychoactive drugs may lead to substance dependence and drug addiction. Drug addiction is a chronically relapsing disorder, and current pharmacological and behavioral therapies are not fully efficient. Attentional bias (AB) is hypothesized to have a causal contribution to substance abuse, addiction development and, maintenance. Transcranial direct current stimulation (tDCS) has been of increasing interest in the past few years as a means for modulating neuroplasticity of the human brain. Although several studies have reported promising therapeutic effects for tDCS in drug abusers, there is no consensus about optimal electrode montages and target brain regions. This study was aimed to compare effectiveness of several electrode montages in modifying AB. Methods and Materials: Ninety early-abstinent methamphetamine users were recruited from several residential drug-rehabilitation centers in Tehran province. They were randomly assigned to six groups with different electrode montages, targeting the left or right dorsolateral prefrontal cortex (DLPFC) as follows: Two conditions with anodal tDCS over the right DLPFC (return electrode placed over the left shoulder or left supraorbital ridge), three conditions with the anode positioned over the left DLPFC (return electrode over the right shoulder, right supraorbital ridge, or contralateral DLPFC), and one sham condition. Active stimulation intensity was 2 mA DC, delivered for 13 min followed by a 20-min rest and another 13 min of stimulation. The probe detection task (PDT) was performed to assess AB. The positive and negative affect scale (PANAS), and the depression anxiety stress scales (DASS) were used to assess baseline affective status before the intervention. Results: Mixed model analysis showed that the left DLPFC/right shoulder and left DLPFC/right DLPFC montages reduced AB toward drug-cues in comparison with sham stimulation. Conclusion: Our findings indicate that anodal stimulation over the left DLPFC reduces AB in methamphetamine users. This study offers promising findings for further studies investigating tDCS as a clinical device to modify AB in drug users.

Differential Activation of the Left and Right Cerebral Hemispheres of Individuals Who Use or are Dependent on Drugs of Abuse

Introduction:

The left and right cerebral hemispheres are not equivalent in performance of cognitive functions associated with risk factors of drug abuse, nor is their development equivalently affected by drugs of abuse. The question addressed here is whether drugs of abuse affect cognitive function as assessed by brain activation, in particular related to impulsivity, and/or whether weaker brain activation associated with impulsivity increases the risk of drug abuse.

Methodology:

Using PubMed and key words, articles were selected that addressed brain activation in individuals who used or abused one of the psychoactive drugs. Findings are summarized.

Results:

For each of the drugs, hypoactivation was found. In some cases this reduced activation was reported predominantly for the right or both hemispheres. There were fewer reports for the left hemisphere.

Discussion and Conclusion:

Rarely do authors focus on why only one or the other hemisphere is affected or why specific structures are affected. Neurobiological differences between the hemispheres and among various brain structures could provide clues to the specific effect of drugs. Increased attention to this gap in research will give additional insights into the etiology of drug abuse and provide direction for treatment.

Neural Correlates of Drug-Biased Choice in Currently Using and Abstinent Individuals With Cocaine Use Disorder

BACKGROUND

The choice for drugs over alternative reinforcers is a translational hallmark feature of drug addiction. The neural basis of such drug-biased choice is not well understood, particularly in individuals with protracted drug abstinence who cannot ethically participate in studies that offer drug-using opportunities.

METHODS

We developed a functional magnetic resonance imaging drug-choice task to examine the choice for viewing drug-related images, rather than for actually consuming a drug. Actively using (n = 18) and abstaining (n = 19) individuals with a history of cocaine use disorder (CUD: dependence or abuse) and matched healthy control subjects (n = 26) participated.

RESULTS

Individuals with CUD, especially those actively using cocaine outside the laboratory, made more choices than control subjects to view images depicting cocaine (especially when directly compared against images depicting an alternative appetitive reinforcer [food]). Functional magnetic resonance imaging data revealed that in individuals with CUD, the act of making drug-related choices engaged brain regions implicated in choice difficulty or ambivalence (i.e., dorsal anterior cingulate cortex, which was higher in all individuals with CUD than control subjects). Drug-related choices in CUD also engaged brain regions implicated in reward (e.g., midbrain/ventral tegmental area, which was most activated in active users, although this region was not hypothesized a priori).

CONCLUSIONS

These results help clarify the neural mechanisms underlying drug-biased choice in human addiction, which, beyond mechanisms involved in value assignment or reward, may critically involve mechanisms that contribute to resolving difficult decisions. Future studies are needed to validate these behavioral and neural abnormalities as markers of drug seeking and relapse in treatment contexts.

Incubation of Accumbal Neuronal Reactivity to Cocaine Cues During Abstinence Predicts Individual Vulnerability to Relapse

An important goal for the treatment of cocaine addiction is to identify neuromarkers that can predict individual vulnerability to relapse after abstinence. There is some evidence that individual reactivity to cue-induced craving may predict subsequent relapse after a period of abstinence. Here we sought to identify the neuronal correlates of this predictive relationship in rats. Rats were trained to self-administer cocaine (6 h) for 16 days to induce escalation of cocaine intake. Then rats underwent a 1-month period of forced abstinence after which they were re-exposed to cocaine self-administration (6 h) for 8 additional days to induce re-escalation of cocaine intake. We recorded nucleus accumbens (NAc) neuronal responses to drug conditioned stimuli (CS) 1 day before and after 1 month of abstinence from cocaine intake escalation. Rats were ranked according to their individual percentage of CS responsive neurons recorded during the last day of abstinence and split by the median into two groups. We found evidence for a robust, incubation-like increase in NAc reactivity to cocaine cues after abstinence only in a subset of individuals (High CS rats). Importantly, compared with other rats that did not present an incubation of NAc reactivity to cocaine cues (Low CS rats), High CS rats were faster to re-escalate their intake of cocaine after abstinence. In addition, after re-escalation, they worked harder and were less sensitive to risk of punishment than Low CS rats, indicating a strengthened motivation to seek and/or take the drug in that group of rats. Overall, these findings indicate that incubation of NAc neuronal reactivity to cocaine cues during abstinence may constitute a predictive neuromarker for individual vulnerability to relapse.