Neural bases of pharmacological treatment of nicotine dependence - insights from functional brain imaging: a systematic review

Clinical efficacy of deep transcranial magnetic stimulation (dTMS) in psychiatric and cognitive disorders: A systematic review

Deep transcranial magnetic stimulation (dTMS) has gained attention as an enhanced form of traditional TMS, targeting broader and deeper regions of the brain. However, a fulsome synthesis of dTMS efficacy across psychiatric and cognitive disorders using sham-controlled trials is lacking. We systematically reviewed 28 clinical trials comparing active dTMS to a sham/controlled condition to characterize dTMS efficacy across diverse psychiatric and cognitive disorders. A comprehensive search of APA PsycINFO, Cochrane, Embase, Medline, and PubMed databases was conducted. Predominant evidence supports dTMS efficacy in patients with obsessive-compulsive disorder (OCD; n = 2), substance use disorders (SUDs; n = 8), and in those experiencing depressive episodes with major depressive disorder (MDD) or bipolar disorder (BD; n = 6). However, the clinical efficacy of dTMS in psychiatric disorders characterized by hyperactivity or hyperarousal (i.e., attention-deficit/hyperactivity disorder, posttraumatic stress disorder, and schizophrenia) was heterogeneous. Common side effects included headaches and pain/discomfort, with rare but serious adverse events such as seizures and suicidal ideation/attempts. Risk of bias ratings indicated a collectively low risk according to the Grading of Recommendations, Assessment, Development, and Evaluations checklist (Meader et al., 2014). Literature suggests promise for dTMS as a beneficial alternative or add-on treatment for patients who do not respond well to traditional treatment, particularly for depressive episodes, OCD, and SUDs. Mixed evidence and limited clinical trials for other psychiatric and cognitive disorders suggest more extensive research is warranted. Future research should examine the durability of dTMS interventions and identify moderators of clinical efficacy.

Changes in distinct brain systems identified with fMRI during smoking cessation treatment with varenicline: a review

BACKGROUND

Varenicline is considered one of the most effective treatment options for smoking cessation. Nonetheless, it is only modestly effective. A deeper comprehension of the effects of varenicline by means of the in-depth review of relevant fMRI studies may assist in paving the development of more targeted and effective treatments.

METHODOLOGY

A search of PubMed and Google Scholar databases was conducted with the keywords "functional magnetic resonance imaging" or "fMRI", and "varenicline". All peer-reviewed articles regarding the assessment of smokers with fMRI while undergoing treatment with varenicline and meeting the predefined criteria were included.

RESULTS

Several studies utilizing different methodologies and targeting different aspects of brain function were identified. During nicotine withdrawal, decreased mesocorticolimbic activity and increased amygdala activity, as well as elevated amygdala-insula and insula-default-mode-network functional connectivity are alleviated by varenicline under specific testing conditions. However, other nicotine withdrawal-induced changes, including the decreased reward responsivity of the ventral striatum, the bilateral dorsal striatum and the anterior cingulate cortex are not influenced by varenicline suggesting a task-dependent divergence in neurocircuitry activation. Under satiety, varenicline treatment is associated with diminished cue-induced activation of the ventral striatum and medial orbitofrontal cortex concomitant with reduced cravings; during the resting state, varenicline induces activation of the lateral orbitofrontal cortex and suppression of the right amygdala.

CONCLUSIONS

The current review provides important clues with regard to the neurobiological mechanism of action of varenicline and highlights promising research opportunities regarding the development of more selective and effective treatments and predictive biomarkers for treatment efficacy.

Combining neuroimaging and brain stimulation to test alternative causal pathways for nicotine addiction in schizophrenia

The smoking rate is high in patients with schizophrenia. Brain stimulation targeting conventional brain circuits associated with nicotine addiction has also yielded mixed results. We aimed to identify alternative circuitries associated with nicotine addiction in both the general population and schizophrenia, and then test whether modulation of such circuitries may alter nicotine addiction behaviors in schizophrenia. In Study I of 40 schizophrenia smokers and 51 non-psychiatric smokers, cross-sectional neuroimaging analysis identified resting state functional connectivity (rsFC) between the dorsomedial prefrontal cortex (dmPFC) and multiple extended amygdala regions to be most robustly associated with nicotine addiction severity in healthy controls and schizophrenia patients (p = 0.006 to 0.07). In Study II with another 30 patient smokers, a proof-of-concept, patient- and rater-blind, randomized, sham-controlled rTMS design was used to test whether targeting the newly identified dmPFC location may causally enhance the rsFC and reduce nicotine addiction in schizophrenia. Although significant interactions were not observed, exploratory analyses showed that this dmPFC-extended amygdala rsFC was enhanced by 4-week active 10Hz rTMS (p = 0.05) compared to baseline; the severity of nicotine addiction showed trends of reduction after 3 and 4 weeks (p ≤ 0.05) of active rTMS compared to sham; Increased rsFC by active rTMS predicted reduction of cigarettes/day (R = -0.56, p = 0.025 uncorrected) and morning smoking severity (R = -0.59, p = 0.016 uncorrected). These results suggest that the dmPFC-extended amygdala circuit may be linked to nicotine addiction in schizophrenia and healthy individuals, and future efforts targeting its underlying pathophysiological mechanisms may yield more effective treatment for nicotine addiction.

Neurobiological associations between smoking and internalizing disorders

People with severe mental disorders have a higher mortality rate due to preventable conditions like cardiovascular diseases and respiratory diseases. Nicotine addiction is a preventable risk factor, with tobacco use being twice as high in people with mental disorders. An integrative model that divides mental disorders into externalising, internalising, and thought disorders could be useful for identifying common causalities and risk factors. This review aims to examine the interface between smoking and internalising disorders, specifically schizophrenia, depressive disorders, and anxiety disorders. The review finds that there is a clear association between smoking behaviour and these disorders. Schizophrenia is associated with polymorphisms that result in an imbalance between glutamate and GABA release and abnormalities of dopaminergic pathways. Nicotine improves dopaminergic signalling and balances glutamatergic and GABAergic pathways, improving symptoms and increasing the risk of nicotine dependence. In depressive disorders, smoking is associated with functional changes in brain regions affected by smoking and self-medication. In anxiety disorders, there is a bidirectional relationship with smoking, involving the amygdala and changes in dopaminergic pathways and cortisol production. Smoking poses a threat to people living with psychiatric disorders and calls for further research to assess the interactions between nicotine dependence and internalising and thought disorders.

Effects of bupropion and SSRI antidepressants on leg movement activity and chin muscle tone during sleep in adolescents

STUDY OBJECTIVES

To evaluate the effects of bupropion on periodic limb movements during sleep (PLMS) and chin electromyography tone in children taking it for their mood disorder, compared to the effects of selective serotonin reuptake inhibitors (SSRIs) and of bupropion combined with SSRIs.

METHODS

Six adolescents (aged 16.0 ± 0.63 years) taking bupropion alone and 6 adolescents (aged 15.9 ± 1.36 years) taking bupropion in combination with an SSRI antidepressant were recruited, along with 10 adolescents (aged 16.2 ± 0.2 years) taking different SSRIs, and they were also enrolled together with 17 age- and sex-matched control patients (aged 15.5 ± 1.26 years). Polysomnographic studies were obtained, and participants' leg movement activity during sleep and muscle tone were assessed quantitatively (atonia index) during all sleep stages.

RESULTS

Participants taking SSRIs showed PLMS indices significantly higher than those of control patients, whereas adolescents taking bupropion showed only slightly increased indexes of nonperiodic leg movements during sleep. No differences in PLMS were observed between adolescents taking bupropion alone or in association with SSRIs. The atonia index showed, within each sleep stage, the lowest values in the 2 groups taking SSRIs and the highest in the control patients; adolescents taking bupropion alone tended to show values slightly smaller than those of the control patients.

CONCLUSIONS

We found that similar to adults, in adolescents SSRIs but not bupropion are associated with increased PLMS. Bupropion also seems to counteract the SSRI-induced increase of PLMS, when administered in combination; thus, the dopaminergic effect of bupropion seems to outmatch the antidopaminergic action of SSRIs. Conversely, bupropion does not counteract the effects of SSRIs on chin electromyography tone.

CITATION

DelRosso LM, Mogavero MP, Fickensher A, Bruni O, Schenck CH, Ferri R. Effects of bupropion and SSRI antidepressants on leg movement activity and chin muscle tone during sleep in adolescents. J Clin Sleep Med. 2023;19(1):151-161.

Gray matter volumes of the insula and anterior cingulate cortex and their dysfunctional roles in cigarette smoking

The salience network, including the insula and anterior cingulate cortex (ACC), has been implicated in nicotine addiction. Structural imaging studies have reported diminished insula and ACC gray matter volumes (GMVs) in smokers as compared to nonsmokers. However, it remains unclear how insula and ACC GMVs may relate to years of smoking, addiction severity, or behavioral traits known to dispose individuals to smoking. Here, with a dataset curated from the Human Connectome Project and voxel-based morphometry, we replicated the findings of smaller GMVs of the insula and medial prefrontal cortex, including the dorsal ACC and supplementary motor area (dACC/SMA), in (70 heavy < 209 light < 209 never) smokers matched in age, sex, and average daily num ber of drinks. The GMVs of the insula or dACC/SMA were not significantly correlated with years of smoking or Fagerstrom Test for Nicotine Dependence (FTND) scores. Heavy relative to never smokers demonstrated higher externalizing and internalizing scores, as evaluated by the NIH Emotion. In heavy smokers, the dACC/SMA but not insula GMV was positively correlated with both externalizing and internalizing scores. The findings together confirm volumetric changes in the salience network in heavy smokers and suggest potentially distinct dysfunctional roles of the insula and dACC/SMA in chronic smoking.

Baclofen attenuates fMRI alcohol cue reactivity in treatment-seeking alcohol dependent individuals

RATIONALE

Baclofen has been shown to effect fMRI alcohol cue reactivity in alcohol dependence, but potential varying effects related to baclofen dose levels have not been examined.

OBJECTIVE

This study investigated whether baclofen attenuates craving and alcohol cue-elicited activation in alcohol-dependent treatment seekers, and the relationship between this response and clinical outcomes (Morley et al. 2018; Morley et al. 2013).

METHODS

Participants included 30 alcohol-dependent individuals who had received daily baclofen 30 mg (n = 11), 75 mg (n = 8) or placebo (n = 11) for at least 2 weeks. Using functional magnetic resonance imaging (fMRI), we examined alcohol cue-elicited neural activation during a visual alcohol cue reactivity task 120 min following treatment administration, and alcohol cue reactivity and percentage of heavy drinking days (% HDD) associations were assessed.

RESULTS

Both baclofen-treated groups reported fewer post-scan % HDD when compared to the placebo-treated group, but no subjective craving group differences were found. Increased alcohol cue-elicited activation was seen in placebo compared to the 75 mg/day baclofen participants in two clusters spanning prefrontal regions implicated in cue reactivity, chiefly frontal regions (i.e., frontal and precentral gyri, anterior cingulate cortex), but no observed alcohol cue reactivity differences between placebo and 30 mg/day baclofen groups. Post-scan % HDD was positively correlated with increased alcohol cue-elicited activation in a cluster encompassing the bilateral caudate nucleus and dorsal anterior cingulate cortex when comparing placebo versus 75 mg/day baclofen groups, and several clusters including prefrontal and mesolimbic regions when comparing placebo versus 30 mg/day baclofen groups.

CONCLUSIONS

Baclofen administration attenuates alcohol cue-elicited activation and reduced the association in baclofen-treated participants between increased activity in key drug cue reactivity regions and higher post-scan % HDD observed in placebo-treated participants, suggesting a dose-specific response effect that may lead to reduced heavy drinking in chronic alcohol-dependent individuals.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT01711125, https://clinicaltrials.gov/ct2/show /NCT01711125.

High-dose baclofen attenuates insula activation during anticipatory anxiety in treatment-seeking alcohol dependant individuals: Preliminary findings from a pharmaco-fMRI study

The GABA _B agonist, baclofen, has been shown to reduce alcohol consumption in patients with alcohol use disorder and also those with comorbid anxiety. This study aimed to evaluate the effect of baclofen versus placebo on the BOLD response during an anticipatory anxiety fMRI task in treatment seeking alcohol patients. Participants included 28 alcohol dependant individuals who had received daily baclofen 30 mg (n = 10), 75 mg (n = 8) or placebo (n = 10) for at least 2 week on a randomized controlled trial (Morley, Leung et al. 2013, Morley, Baillie et al. 2018). Using functional magnetic resonance imaging (fMRI), we examined threat cue-elicited neural activation during a threat reactivity task 120 min following administration of BAC (30 mg or 75 mg) or placebo. Whole-brain analyses revealed no significant differences between the combined BAC doses versus PL. However, there were significant decreases in anticipatory threat cue-elicited activation observed in BAC 75 mg/day compared to PL participants in the insula. In response to threat cues, high dose (75 mg/day) baclofen administration attenuates activation in the insula and inferior frontal gyrus, relative to placebo. These preliminary findings suggests that modulating emotional regulation and attentional allocation during high threat stimuli may be mediated by GABA _B receptors and may be a potential mechanism of action for baclofen's beneficial treatment effects for alcohol use disorder.

Parsing inter- and intra-individual variability in key nervous system mechanisms of stress responsivity and across functional domains

Exposure to stressful events is omnipresent in modern human life, yet people show considerable heterogeneity in the impact of stress exposure(s) on their functionality and overall health. Encounter with stressor(s) is counteracted by an intricate repertoire of nervous-system responses. This narrative review starts with a brief summary of the vast evidence that supports heart rate variability, cortisol secretion, and large-scale cortical network interactions as kay physiological, endocrinological, and neural mechanisms of stress responsivity, respectively. The second section highlights potential sources for inter-individual variability in these mechanisms, by focusing on biological, environmental, social, habitual, and psychological factors that may influence stress responsivity patterns and thus contribute to heterogeneity in the impact of stress exposure on functionality and health. The third section introduces intra-individually variability in stress responsivity across functional domains as a novel putative source for heterogeneity in the impact of stress exposure. Challenges and future directions are further discussed. Parsing inter- and intra-individual variability in nervous-system mechanisms of stress responsivity and across functional domains is critical towards potential clinical translation.

Transdiagnostic Effects of Ventromedial Prefrontal Cortex Transcranial Magnetic Stimulation on Cue Reactivity

BACKGROUND

Elevated frontal and striatal reactivity to drug cues is a transdiagnostic hallmark of substance use disorders. The goal of these experiments was to determine if it is possible to decrease frontal and striatal reactivity to drug cues in both cocaine users and heavy alcohol users through continuous theta burst stimulation (cTBS) to the left ventromedial prefrontal cortex (VMPFC).

METHODS

Two single-blinded, within-subject, active sham-controlled experiments were performed wherein neural reactivity to drug/alcohol cues versus neutral cues was evaluated immediately before and after receiving real or sham cTBS (110% resting motor threshold, 3600 pulses, Fp1 location; N = 49: 25 cocaine users [experiment 1], 24 alcohol users [experiment 2]; 196 total functional magnetic resonance imaging scans). Generalized psychophysiological interaction and three-way repeated-measures analysis of variance were used to evaluate cTBS-induced changes in drug cue-associated functional connectivity between the left VMPFC and eight regions of interest: ventral striatum, left and right caudate, left and right putamen, left and right insula, and anterior cingulate cortex.

RESULTS

In both experiments, there was a significant interaction between treatment (real/sham) and time (pre/post). In both experiments, cue-related functional connectivity was significantly attenuated following real cTBS versus sham cTBS. There was no significant interaction with region of interest for either experiment.

CONCLUSIONS

This is the first sham-controlled investigation to demonstrate, in two populations, that VMPFC cTBS can attenuate neural reactivity to drug and alcohol cues in frontostriatal circuits. These results provide an empirical foundation for future clinical trials that may evaluate the efficacy, durability, and clinical implications of VMPFC cTBS to treat addictions.

Pharmacological intervention and abstinence in smokers undergoing cessation treatment: A psychophysiological study

As a composite concept, negative affect comprises various aversive emotional experiences, such as irritability and nervousness. It is a critical motivational factor that helps maintain smoking behavior, and contributes significantly to smoking cessation failure as a core withdrawal symptom. Prior research has indicated an important role of nicotinic mechanisms in negative affect processing. The most effective smoking cessation medication, varenicline, targets nicotinic acetylcholine receptors (nAChRs) as a partial agonist, while another first-line cessation medication, bupropion, has shown antagonistic effects on nAChRs. Therefore, it is possible that both medications work to reduce smoking behavior through modulating negative affect processing. To evaluate this hypothesis, we examined the impact of varenicline tartrate and bupropion hydrochloride sustained-release on electrophysiological responses to affective, cigarette-related, and neutral cues before and during smoking cessation treatment in a randomized placebo-controlled clinical trial. The participants were 206 smokers, a subset of 294 participants that were enrolled in a larger smoking cessation clinical trial who were randomly assigned to one medication group for 12weeks. Orbicularis oculi (startle eyeblink response) and corrugator supercilii facial electromyographic (EMG) reactivity toward emotional pictures (i.e., pleasant and unpleasant) in a picture-viewing task were measured before treatment and 2 and 6weeks after treatment was started. The startle and corrugator EMG activities increase with the exposure to unpleasant cues, and served as indices for negative emotional reactivity (NER). We found that after 6weeks, drug reduced startle-related NER in the varenicline group, but not in the bupropion or placebo group. Independent of medication treatment, lower baseline NER, as measured by the corrugator EMG activity, predicted a higher likelihood of smoking abstinence 1 and 3months after quitting smoking. These findings indicate the important roles of varenicline in negative affect processing and negative emotional reactivity in the course of smoking cessation.

Chronic cigarette smoking is linked with structural alterations in brain regions showing acute nicotinic drug-induced functional modulations

Background

Whereas acute nicotine administration alters brain function which may, in turn, contribute to enhanced attention and performance, chronic cigarette smoking is linked with regional brain atrophy and poorer cognition. However, results from structural magnetic resonance imaging (MRI) studies comparing smokers versus nonsmokers have been inconsistent and measures of gray matter possess limited ability to inform functional relations or behavioral implications. The purpose of this study was to address these interpretational challenges through meta-analytic techniques in the service of clarifying the impact of chronic smoking on gray matter integrity and more fully contextualizing such structural alterations.

Methods

We first conducted a coordinate-based meta-analysis of structural MRI studies to identify consistent structural alterations associated with chronic smoking. Subsequently, we conducted two additional meta-analytic assessments to enhance insight into potential functional and behavioral relations. Specifically, we performed a multimodal meta-analytic assessment to test the structural–functional hypothesis that smoking-related structural alterations overlapped those same regions showing acute nicotinic drug-induced functional modulations. Finally, we employed database driven tools to identify pairs of structurally impacted regions that were also functionally related via meta-analytic connectivity modeling, and then delineated behavioral phenomena associated with such functional interactions via behavioral decoding.

Results

Across studies, smoking was associated with convergent structural decreases in the left insula, right cerebellum, parahippocampus, multiple prefrontal cortex (PFC) regions, and the thalamus. Indicating a structural–functional relation, we observed that smoking-related gray matter decreases overlapped with the acute functional effects of nicotinic agonist administration in the left insula, ventromedial PFC, and mediodorsal thalamus. Suggesting structural-behavioral implications, we observed that the left insula’s task-based, functional interactions with multiple other structurally impacted regions were linked with pain perception, the right cerebellum’s interactions with other regions were associated with overt body movements, interactions between the parahippocampus and thalamus were linked with memory processes, and interactions between medial PFC regions were associated with face processing.

Conclusions

Collectively, these findings emphasize brain regions (e.g., ventromedial PFC, insula, thalamus) critically linked with cigarette smoking, suggest neuroimaging paradigms warranting additional consideration among smokers (e.g., pain processing), and highlight regions in need of further elucidation in addiction (e.g., cerebellum).

Electronic supplementary material

The online version of this article (doi:10.1186/s12993-016-0100-5) contains supplementary material, which is available to authorized users.

Atomoxetine could improve intra-individual variability in drug-naïve adults with attention-deficit/hyperactivity disorder comparably with methylphenidate: A head-to-head randomized clinical trial

OBJECTIVE

Intra-individual variability in reaction time (IIV-RT) is common in individuals with attention-deficit/hyperactivity disorder (ADHD). It can be improved by stimulants. However, the effects of atomoxetine on IIV-RT are inconclusive. We aimed to investigate the effects of atomoxetine on IIV-RT, and directly compared its efficacy with methylphenidate in adults with ADHD.

METHODS

An 8-10 week, open-label, head-to-head, randomized clinical trial was conducted in 52 drug-naïve adults with ADHD, who were randomly assigned to two treatment groups: immediate-release methylphenidate (n=26) thrice daily (10-20 mg per dose) and atomoxetine once daily (n=26) (0.5-1.2 mg/kg/day). IIV-RT, derived from the Conners' continuous performance test (CCPT), was represented by the Gaussian (reaction time standard error, RTSE) and ex-Gaussian models (sigma and tau). Other neuropsychological functions, including response errors and mean of reaction time, were also measured. Participants received CCPT assessments at baseline and week 8-10 (60.4±6.3 days).

RESULTS

We found comparable improvements in performances of CCPT between the immediate-release methylphenidate- and atomoxetine-treated groups. Both medications significantly improved IIV-RT in terms of reducing tau values with comparable efficacy. In addition, both medications significantly improved inhibitory control by reducing commission errors.

CONCLUSION

Our results provide evidence to support that atomoxetine could improve IIV-RT and inhibitory control, of comparable efficacy with immediate-release methylphenidate, in drug-naïve adults with ADHD. Shared and unique mechanisms underpinning these medication effects on IIV-RT awaits further investigation.

Association of Long-Term Nicotine Abstinence With Normal Metabotropic Glutamate Receptor-5 Binding

BACKGROUND

Nicotine addiction is a major public health problem and is associated with primary glutamatergic dysfunction. We recently showed marked global reductions in metabotropic glutamate receptor type 5 (mGluR5) binding in smokers and recent ex-smokers (average abstinence duration of 25 weeks). The goal of this study was to examine the role of mGluR5 downregulation in nicotine addiction by investigating a group of long-term ex-smokers (abstinence >1.5 years), and to explore associations between mGluR5 binding and relapse in recent ex-smokers.

METHODS

Images of mGluR5 receptor binding were acquired in 14 long-term ex-smokers, using positron emission tomography with radiolabeled [11C]ABP688, which binds to an allosteric site with high specificity.

RESULTS

Long-term ex-smokers and individuals who had never smoked showed no differences in mGluR5 binding in any of the brain regions examined. Long-term ex-smokers showed significantly higher mGluR5 binding than recent ex-smokers, most prominently in the frontal cortex (42%) and thalamus (57%).

CONCLUSIONS

Our findings suggest that downregulation of mGluR5 is a pathogenetic mechanism underlying nicotine dependence and the high relapse rate in individuals previously exposed to nicotine. Therefore, mGluR5 receptor binding appears to be an effective biomarker in smoking and a promising target for the discovery of novel medication for nicotine dependence and other substance-related disorders.

Noninvasive brain stimulation treatments for addiction and major depression

Major depressive disorder (MDD) and substance use disorders (SUDs) are prevalent, disabling, and challenging illnesses for which new treatment options are needed, particularly in comorbid cases. Neuroimaging studies of the functional architecture of the brain suggest common neural substrates underlying MDD and SUDs. Intrinsic brain activity is organized into a set of functional networks, of which two are particularly relevant to psychiatry. The salience network (SN) is crucial for cognitive control and response inhibition, and deficits in SN function are implicated across a wide variety of psychiatric disorders, including MDD and SUDs. The ventromedial network (VMN) corresponds to the classic reward circuit, and pathological VMN activity for drug cues/negative stimuli is seen in SUDs/MDD. Noninvasive brain stimulation (NIBS) techniques, including rTMS and tDCS, have been used to enhance cortico–striatal–thalamic activity through the core SN nodes in the dorsal anterior cingulate cortex, dorsolateral prefrontal cortex, and anterior insula. Improvements in both MDD and SUD symptoms ensue, including in comorbid cases, via enhanced cognitive control. Inhibition of the VMN also appears promising in preclinical studies for quenching the pathological incentive salience underlying SUDs and MDD. Evolving techniques may further enhance the efficacy of NIBS for MDD and SUD cases that are unresponsive to conventional treatments.

Tobacco smoking: From 'glamour' to 'stigma'. A comprehensive review

In this narrative review, we explore the history of tobacco smoking, its associations and portrayal of its use with luxury and glamour in the past, and intriguingly, its subsequent transformation into a mass consumption industrialized product encouraged by advertising and film. Then, we describe the next phase where tobacco in parts of the world has become an unwanted product. However, the number of smokers is still increasing, especially in new markets, and increasingly younger individuals are being attracted to it, despite the well-known health consequences of tobacco use. We also explore current smoking behaviors, looking at trends in the prevalence of consumption throughout the world, discrimination against smokers, light and/or intermittent smokers, and the electronic cigarette (e-cigarette). We place these changes in the context of neuroscience, which may help explain why the cognitive effects of smoking can be important reinforcers for its consumption despite strong anti-smoking pressure in Western countries.

Neural substrates of cue reactivity: association with treatment outcomes and relapse

Given the strong evidence for neurological alterations at the basis of drug dependence, functional magnetic resonance imaging (fMRI) represents an important tool in the clinical neuroscience of addiction. fMRI cue-reactivity paradigms represent an ideal platform to probe the involvement of neurobiological pathways subserving the reward/motivation system in addiction and potentially offer a translational mechanism by which interventions and behavioral predictions can be tested. Thus, this review summarizes the research that has applied fMRI cue-reactivity paradigms to the study of adult substance use disorder treatment responses. Studies utilizing fMRI cue-reactivity paradigms for the prediction of relapse and as a means to investigate psychosocial and pharmacological treatment effects on cue-elicited brain activation are presented within four primary categories of substances: alcohol, nicotine, cocaine and opioids. Lastly, suggestions for how to leverage fMRI technology to advance addiction science and treatment development are provided.

Neurobiological impact of nicotinic acetylcholine receptor agonists: an activation likelihood estimation meta-analysis of pharmacologic neuroimaging studies

BACKGROUND

Nicotinic acetylcholine receptor (nAChR) agonists augment cognition among cigarette smokers and nonsmokers, yet the systems-level neurobiological mechanisms underlying such improvements are not fully understood. Aggregating neuroimaging results regarding nAChR agonists provides a means to identify common functional brain changes that may be related to procognitive drug effects.

METHODS

We conducted a meta-analysis of pharmacologic neuroimaging studies within the activation likelihood estimation framework. We identified published studies contrasting a nAChR drug condition versus a baseline and coded each contrast by activity change direction (decrease or increase), participant characteristics (smokers or nonsmokers), and drug manipulation employed (pharmacologic administration or cigarette smoking).

RESULTS

When considering all studies, nAChR agonist administration was associated with activity decreases in multiple regions, including the ventromedial prefrontal cortex (vmPFC), posterior cingulate cortex (PCC), parahippocampus, insula, and the parietal and precentral cortices. Conversely, activity increases were observed in lateral frontoparietal cortices, the anterior cingulate cortex, thalamus, and cuneus. Exploratory analyses indicated that both smokers and nonsmokers showed activity decreases in the vmPFC and PCC, and increases in lateral frontoparietal regions. Among smokers, both pharmacologic administration and cigarette smoking were associated with activity decreases in the vmPFC, PCC, and insula and increases in the lateral PFC, dorsal anterior cingulate cortex, thalamus, and cuneus.

CONCLUSIONS

These results provide support for the systems-level perspective that nAChR agonists suppress activity in default-mode network regions and enhance activity in executive control network regions in addition to reducing activation of some task-related regions. We speculate these are potential mechanisms by which nAChR agonists enhance cognition.

An Official American Thoracic Society Research Statement: Current Understanding and Future Research Needs in Tobacco Control and Treatment

INTRODUCTION

Since the mid-20th century, the scientific community has substantially improved its understanding of the worldwide tobacco epidemic. Although significant progress has been made, the sheer enormity and scope of the global problem put it on track to take a billion lives this century. Curbing the epidemic will require maximizing the impact of proven tools as well as the development of new, breakthrough methods to help interrupt the spread of nicotine addiction and reduce the downstream morbidity.

METHODS

Members of the Tobacco Action Committee of the American Thoracic Society queried bibliographic databases, including Medline, Embase, and the Cochrane Collaborative, to identify primary sources and reviews relevant to the epidemic. Exploded search terms were used to identify evidence, including tobacco, addiction, smoking, cigarettes, nicotine, and smoking cessation. Evidence was consolidated into three thematic areas: (1) determinants of risk, (2) maternal-fetal exposure, and (3) current tobacco users. Expert panel consensus regarding current gaps in understanding and recommendations for future research priorities was generated through iterative discussion.

RESULTS

Although much has been accomplished, significant gaps in understanding remain. Implementation often lags well behind insight. This report identifies a number of investigative opportunities for significantly reducing the toll of tobacco use, including: (1) the need for novel, nonlinear models of population-based disease control; (2) refinement of "real-world" models of clinical intervention in trial design; and (3) understanding of mechanisms by which intrauterine smoke exposure may lead to persistent, tobacco-related chronic disease.

DISCUSSION

In the coming era of tobacco research, pooled talent from multiple disciplines will be required to further illuminate the complex social, environmental and biological codeterminants of tobacco dependence.

Decreased Nicotinic Receptor Availability in Smokers with Slow Rates of Nicotine Metabolism

The nicotine metabolite ratio (NMR), a stable measure of hepatic nicotine metabolism via the CYP2A6 pathway and total nicotine clearance, is a predictive biomarker of response to nicotine replacement therapy, with increased quit rates in slower metabolizers. Nicotine binds directly to nicotinic acetylcholine receptors (nAChRs) to exert its psychoactive effects. This study examined the relationship between NMR and nAChR (α4β2* subtype) availability using PET imaging of the radiotracer 2-(18)F-fluoro-3-(2(S)-azetidinylmethoxy)pyridine (2-(18)F-FA-85380, or 2-(18)F-FA).

METHODS

Twenty-four smokers-12 slow metabolizers (NMR < 0.26) and 12 normal metabolizers (NMR ≥ 0.26)-underwent 2-(18)F-FA-PET brain imaging after overnight nicotine abstinence (18 h before scanning), using a validated bolus-plus-infusion protocol. Availability of nAChRs was compared between NMR groups in a priori volumes of interest, with total distribution volume (VT/fP) being the measure of nAChR availability. Cravings to smoke were assessed before and after the scans.

RESULTS

Thalamic nAChR α4β2* availability was significantly reduced in slow nicotine metabolizers (P = 0.04). Slow metabolizers exhibited greater reductions in cravings after scanning than normal metabolizers; however, craving was unrelated to nAChR availability.

CONCLUSION

The rate of nicotine metabolism is associated with thalamic nAChR availability. Additional studies could examine whether altered nAChR availability underlies the differences in treatment response between slow and normal metabolizers of nicotine.

Genetic and environmental contributions to the relationships between brain structure and average lifetime cigarette use

Chronic cigarette use has been consistently associated with differences in the neuroanatomy of smokers relative to nonsmokers in case-control studies. However, the etiology underlying the relationships between brain structure and cigarette use is unclear. A community-based sample of male twin pairs ages 51-59 (110 monozygotic pairs, 92 dizygotic pairs) was used to determine the extent to which there are common genetic and environmental influences between brain structure and average lifetime cigarette use. Brain structure was measured by high-resolution structural magnetic resonance imaging, from which subcortical volume and cortical volume, thickness and surface area were derived. Bivariate genetic models were fitted between these measures and average lifetime cigarette use measured as cigarette pack-years. Widespread, negative phenotypic correlations were detected between cigarette pack-years and several cortical as well as subcortical structures. Shared genetic and unique environmental factors contributed to the phenotypic correlations shared between cigarette pack-years and subcortical volume as well as cortical volume and surface area. Brain structures involved in many of the correlations were previously reported to play a role in specific aspects of networks of smoking-related behaviors. These results provide evidence for conducting future research on the etiology of smoking-related behaviors using measures of brain morphology.

Dopamine function in cigarette smokers: an [¹⁸F]-DOPA PET study

Tobacco addiction is a global public health problem. Addiction to tobacco is thought to involve the effects of nicotine on the dopaminergic system. Only one study has previously investigated dopamine synthesis capacity in cigarette smokers. This study, exclusively in male volunteers, reported increased dopamine synthesis capacity in heavy smokers compared with non-smokers. We sought to determine whether dopamine synthesis capacity was elevated in a larger sample of cigarette smokers that included females. Dopamine synthesis capacity was measured in 15 daily moderate smokers with 15 sex- and age-matched control subjects who had never smoked tobacco. Dopamine synthesis capacity (indexed as the influx rate constant K(i)(cer)) was measured with positron emission tomography and 3,4-dihydroxy-6-[(18)F]-fluoro-l-phenylalanine. There was no significant group difference in dopamine synthesis capacity between smokers and non-smoker controls in the whole striatum (t28=0.64, p=0.53) or any of its functional subdivisions. In smokers, there were no significant relationships between the number of cigarettes smoked per day and dopamine synthesis capacity in the whole striatum (r=-0.23, p=0.41) or any striatal subdivision. These findings indicate that moderate smoking is not associated with altered striatal dopamine synthesis capacity.

Retention predictors of a smoking treatment provided by a public psychosocial unit in Brazil

Psychosocial units in Brazil (CAPS) provide access to mental health and addiction patients, who are not routinely treated for nicotine dependence. The present study analysed predictors of retention of a 6-week treatment provided by a CAPS unit to 367 smokers with a high rate of psychiatric disorders and addictions for the period 2007-2010. Several baseline variables were collected. Retention was defined as the presence of the individual in all four medical consultations and six group sessions. Multivariate discrete time Cox survival regression models were used to test for the outcome of interest. Timetables were used to explore in which moment of the treatment each predictor was important. Time to smoking the first cigarette (TTFC) 5 min or later after waking and nicotine patch use (nicotine replacement therapy, NRT) were associated with retention. The present study supports the importance of the variables TTFC and NRT when used in treatment retention for a sample with a high rate of psychiatric and alcohol disorders. NRT seems to be very important in the beginning of the treatment, probably because of withdrawal symptoms. Individuals currently undergoing psychiatric treatment and with alcohol problems had good retention rates comparable to the other individuals.

Neuroimagem na dependência de jogos eletrônicos: uma revisão sistemática

Objetivo: Realizar revisão sistemática de manuscritos que utilizaram a neuroimagem no estudo da dependência de jogos eletrônicos, a fim de identificar as principais regiões cerebrais alteradas. Métodos: Foram realizadas buscas nos seguintes bancos de dados: ScieELO, BVS, Lilacs, Science Direct On Line e PubMed. Não houve data mínima para a pesquisa, sendo considerados os artigos encontrados até julho de 2013. Os descritores utilizados para a presente revisão sistemática da literatura foram: “PET”, “SPECT”, “MRI”, “DTI”, “EEG”, “imaging”, “neuroimaging”, “spectroscopy”, “functional magnetic ressonance”, “structural magnetic ressonance”, “tractography”, “voxel” e “brain”, individualmente cruzados com os descritores “gaming” e “video game addiction”. Resultados: Dos 52 artigos encontrados, 16 foram selecionados: nove usaram fMRI, quatro usaram sRMI, um usou PET e dois usaram EEG. Em relação às alterações funcionais e estruturais, elas foram mais observadas no lobo frontal (córtex pré-frontal dorsolateral, córtex orbitofrontal, giro pré-frontal, giro frontal médio), parietal, temporal (giro para-hipocampal), núcleos da base, tálamo, ínsula e cerebelo. Conclusão: A despeito dos métodos utilizados, os estudos apontaram convergências quanto às reciprocidades cerebrais. Essas alterações neurais são semelhantes às observadas em pacientes dependentes de substâncias e de internet, especialmente durante o estado de fissura. Apesar de apenas recentemente pesquisas de neuroimagem em dependentes de jogos eletrônicos terem sido realizadas, contamos no momento com achados significativos alinhados à compreensão dos mecanismos neurais associados à dependência de jogos eletrônicos e respectiva inserção como categoria nosológica no âmbito psiquiátrico.

Nicotine-Cadmium Interaction Alters Exploratory Motor Function and Increased Anxiety in Adult Male Mice

In this study we evaluated the time dependence in cadmium-nicotine interaction and its effect on motor function, anxiety linked behavioural changes, serum electrolytes, and weight after acute and chronic treatment in adult male mice. Animals were separated randomly into four groups of n = 6 animals each. Treatment was done with nicotine, cadmium, or nicotine-cadmium for 21 days. A fourth group received normal saline for the same duration (control). Average weight was determined at 7-day interval for the acute (D1-D7) and chronic (D7-D21) treatment phases. Similarly, the behavioural tests for exploratory motor function (open field test) and anxiety were evaluated. Serum electrolytes were measured after the chronic phase. Nicotine, cadmium, and nicotine-cadmium treatments caused no significant change in body weight after the acute phase while cadmium-nicotine and cadmium caused a decline in weight after the chronic phase. This suggests the role of cadmium in the weight loss observed in tobacco smoke users. Both nicotine and cadmium raised serum Ca²⁺ concentration and had no significant effect on K⁺ ion when compared with the control. In addition, nicotine-cadmium treatment increased bioaccumulation of Cd²⁺ in the serum which corresponded to a decrease in body weight, motor function, and an increase in anxiety.

Prospective Evaluation of Factors Predicting Nicotine Withdrawal Symptoms Among Korean Americans

INTRODUCTION

This study examined factors predicting nicotine withdrawal symptoms following quitting among Korean American smokers who were receiving counseling and nicotine replacement therapy.

METHODS

The sample comprised 90 Korean American smokers selected from a two-arm randomised controlled trial of a smoking cessation intervention (culturally adapted versus treatment as usual). Nicotine withdrawal symptoms were assessed weekly for the first four weeks from the target quit day, using the Minnesota Nicotine Withdrawal Scale (MNWS). Only those who participated in two or more weekly assessments of the symptoms were included.

RESULTS

Among the nine withdrawal symptoms listed in the MNWS, craving and disturbed sleep decreased over time whereas the remaining symptoms had no significant effect of time. Women or individuals who perceived greater risks of quitting smoking reported more withdrawal symptoms after controlling for abstinence status. Although withdrawal symptoms did not change, on average, with time, the rates of change varied randomly across individuals. Women reported more withdrawal symptoms in the first week after quitting and showed a higher rate of decline of the symptoms over time than men.

CONCLUSIONS

Korean American smokers who are women or who perceive greater risks of quitting smoking may require more intensive treatment to effectively deal with post-quit withdrawal symptoms.