Smoking-related cue-induced brain activation in adolescent light smokers

Methylphenidate as a treatment option for substance use disorder: a transdiagnostic perspective

A transition in viewing mental disorders from conditions defined as a set of unique characteristics to one of the quantitative variations on a collection of dimensions allows overlap between disorders. The overlap can be utilized to extend to treatment approaches. Here, we consider the overlap between attention-deficit/hyperactivity disorder and substance use disorder to probe the suitability to use methylphenidate as a treatment for substance use disorder. Both disorders are characterized by maladaptive goal-directed behavior, impaired cognitive control, hyperactive phasic dopaminergic neurotransmission in the striatum, prefrontal hypoactivation, and reduced frontal cortex gray matter volume/density. In addition, methylphenidate has been shown to improve cognitive control and normalize associated brain activation in substance use disorder patients and clinical trials have found methylphenidate to improve clinical outcomes. Despite the theoretical basis and promising, but preliminary, outcomes, many questions remain unanswered. Most prominent is whether all patients who are addicted to different substances may equally profit from methylphenidate treatment.

The effect of exposure to tobacco smoking-related media messages on youths' smoking behavior in Jordan: A longitudinal, school-based study

Only a few studies investigated the link between tobacco smoking-related media and youth smoking in the Eastern Mediterranean Region (EMR). This study aimed to assess the influence of both promotional and control messages on cigarette smoking behavior among young Jordanian students. Generalized Linear Mixed Models were analyzed using data from the Irbid Longitudinal Smoking Study that followed a random sample of 2174 students (2008-2011). We examined the associations of media messaging with smoking behavior, as well as intention-to-quit smoking, and intention-to-start smoking, among young adolescents. At baseline, 12.2% and 43.7% of students were exposed to only pro-smoking or only anti-smoking messages, while 41.8% were equally exposed to both. Exposure to anti-smoking messages was associated with lower odds of ever smoking at baseline among girls (AOR = 0.4; 95% CI: 0.2, 0.8). Boys who were exposed to anti-smoking messages were more likely to report an intention to quit, with borderline significance (AOR = 2.0; 95% CI: 0.9, 4.1). The cumulative exposure to anti-smoking messages over time was associated with lower odds of intention to smoke among girls (AOR = 0.5; 95% CI: 0.3, 0.9) but with higher odds among boys (AOR = 1.8; 95% CI: 1.0, 3.1). In both sexes, media messaging was not associated with progression of the smoking habit. In conclusion, this comprehensive analysis of both pro- and anti-smoking messages advances our understanding of their role in influencing youths' smoking behaviors, and could guide the development of evidence-based interventions to address adolescent tobacco smoking in Jordan and the EMR.

Effects of acute aerobic exercise on food-reward mechanisms in smoking-addicted individuals: An fNIRS study

PURPOSE

In addition to its toxic effects on the human cardiovascular and respiratory systems, tobacco dependence also causes damage to brain function and cognitive activity. Therefore, the main objective of this study was to investigate the effects of acute aerobic exercise on food-reward function and its food-cued prefrontal brain activation in tobacco-dependent individuals.

METHOD

Ninety-three participants who met the study criteria were randomly divided into a moderate-intensity exercise group (65%-75% HRmax), a high-intensity exercise group (75%-85% HRmax), and a quiet control group (n = 31 in each group). Participants were asked to perform a 35-minute target-intensity exercise or rest. The participants took the Leeds Food Preference Questionnaire and the Visual Food Cues Paradigm Task immediately before the experiment and immediately after completing the exercise or control intervention, and oxyhemoglobin concentrations in each prefrontal brain region were measured at the same time as the Visual Food Cues Paradigm Task.

RESULTS

Acute aerobic exercise significantly increased implicit cravings for low-calorie sweets in nicotine-dependent individuals (high: p = 0.040; moderate: p = 0.001), while acute moderate-intensity aerobic exercise also significantly increased the activation levels of the left dorsolateral prefrontal cortex (DLPFC: CH15: p = 0.030; CH22: p = 0.003) as well as the left orbitofrontal area (OFC: CH21: p = 0.007) in the food-reward brain region in nicotine-dependent individuals.

CONCLUSION

Acute aerobic exercise improves food-reward function and effectively increases activation levels in the DLPFC and OFC cerebral cortex in tobacco-dependent individuals, facilitating restoration of sensitivity to their drug-hijacked natural reward circuits.

A methodological checklist for fMRI drug cue reactivity studies: development and expert consensus

Cue reactivity is one of the most frequently used paradigms in functional magnetic resonance imaging (fMRI) studies of substance use disorders (SUDs). Although there have been promising results elucidating the neurocognitive mechanisms of SUDs and SUD treatments, the interpretability and reproducibility of these studies is limited by incomplete reporting of participants' characteristics, task design, craving assessment, scanning preparation and analysis decisions in fMRI drug cue reactivity (FDCR) experiments. This hampers clinical translation, not least because systematic review and meta-analysis of published work are difficult. This consensus paper and Delphi study aims to outline the important methodological aspects of FDCR research, present structured recommendations for more comprehensive methods reporting and review the FDCR literature to assess the reporting of items that are deemed important. Forty-five FDCR scientists from around the world participated in this study. First, an initial checklist of items deemed important in FDCR studies was developed by several members of the Enhanced NeuroImaging Genetics through Meta-Analyses (ENIGMA) Addiction working group on the basis of a systematic review. Using a modified Delphi consensus method, all experts were asked to comment on, revise or add items to the initial checklist, and then to rate the importance of each item in subsequent rounds. The reporting status of the items in the final checklist was investigated in 108 recently published FDCR studies identified through a systematic review. By the final round, 38 items reached the consensus threshold and were classified under seven major categories: 'Participants' Characteristics', 'General fMRI Information', 'General Task Information', 'Cue Information', 'Craving Assessment Inside Scanner', 'Craving Assessment Outside Scanner' and 'Pre- and Post-Scanning Considerations'. The review of the 108 FDCR papers revealed significant gaps in the reporting of the items considered important by the experts. For instance, whereas items in the 'General fMRI Information' category were reported in 90.5% of the reviewed papers, items in the 'Pre- and Post-Scanning Considerations' category were reported by only 44.7% of reviewed FDCR studies. Considering the notable and sometimes unexpected gaps in the reporting of items deemed to be important by experts in any FDCR study, the protocols could benefit from the adoption of reporting standards. This checklist, a living document to be updated as the field and its methods advance, can help improve experimental design, reporting and the widespread understanding of the FDCR protocols. This checklist can also provide a sample for developing consensus statements for protocols in other areas of task-based fMRI.

More than just statics: Temporal dynamic changes of intrinsic brain activity in cigarette smoking

Smoking is companied with altered intrinsic activity of the brain measured by amplitude of low-frequency fluctuation. Evidence has revealed that human brain activity is a highly dynamic and rapidly changing system. How exactly cigarette smoking affect temporal dynamic intrinsic brain activity is not fully understood nor is it clear how smoking severity influences spontaneous brain activity. Dynamic amplitude of low-frequency fluctuation (dALFF) was used to examine the dynamic temporal variability in 93 participants (63 smokers, 30 nonsmokers). We further divided smokers into light and heavy smokers. The temporal variability in intrinsic brain activity among these groups was compared. Correlation analyses were performed between dALFF in areas showing group differences and smoking behaviour (e.g., the Fagerström Test for Nicotine Dependence [FTND] scores and pack-years). Smokers showed significantly increased dALFF in the left inferior/middle frontal gyrus, right orbitofrontal gyrus, right insula, left superior/medial frontal gyrus and right middle frontal gyrus than nonsmokers. Light smokers showed increased dALFF variability in the left prefrontal cortex. Heavy smokers showed increased dynamics in specific brain regions, including the right postcentral gyrus, right insula and left precentral gyrus. Furthermore, the temporal variability in dALFF in the left superior/medial frontal gyrus, left superior/middle frontal gyrus, right middle frontal gyrus and right insula was positively correlated with pack-years or FTND. Combined, these results suggest that smokers increase stable and persistent spontaneous brain activity in prefrontal cortex, involved impaired gold-directed action and value-based decision-making. In addition, individuals with heavier smoking severity show increased perturbance on spontaneous brain activity of perception and sensorimotor, related to increased reliance.

Molecular and neuronal mechanisms underlying the effects of adolescent nicotine exposure on anxiety and mood disorders

Tobacco addiction is highly co-morbid with a variety of mental health conditions, including schizophrenia, mood and anxiety disorders. Nicotine, the primary psychoactive compound in tobacco-related products is known to functionally modulate brain circuits that are disturbed in these disorders. Nicotine can potently regulate the transmission of various neurochemicals, including dopamine (DA), γ-amino-butyric acid (GABA) and glutamate, within various mesocorticolimbic structures, such as the ventral tegmental area (VTA), nucleus accumbens (NAc) and prefrontal cortex (PFC), all of which show pathologies in these disorders. Many neuropsychiatric diseases have etiological origins during neurodevelopment, typically occurring during vulnerable periods of adolescent or pre-natal brain development. During these neurodevelopmental periods, exposure to extrinsic drug insults can induce enduring and long-term pathophysiological sequelae that ultimately increase the risk of developing chronic mental health disorders in later life. These vulnerability factors are of growing concern given rising rates of adolescent nicotine exposure via traditional tobacco use and the increasing use of alternative nicotine delivery formats such as vaping and e-cigarettes. A large body of clinical and pre-clinical evidence points to an important role for adolescent exposure to nicotine and increased vulnerability to developing mood and anxiety disorders in later life. This review will examine current clinical and pre-clinical evidence that pinpoints specific mechanisms within the mesocorticolimbic circuitry and molecular biomarkers linked to the association between adolescent nicotine exposure and increased risk of developing mood and anxiety-related disorders. This article is part of the special issue on 'Vulnerabilities to Substance Abuse'.

Adolescent Substance Use and the Brain: Behavioral, Cognitive and Neuroimaging Correlates

Adolescence is an important ontogenetic period that is characterized by behaviors such as enhanced novelty-seeking, impulsivity, and reward preference, which can give rise to an increased risk for substance use. While substance use rates in adolescence are generally on a decline, the current rates combined with emerging trends, such as increases in e-cigarette use, remain a significant public health concern. In this review, we focus on the neurobiological divergences associated with adolescent substance use, derived from a cross-sectional, retrospective, and longitudinal studies, and highlight how the use of these substances during adolescence may relate to behavioral and neuroimaging-based outcomes. Identifying and understanding the associations between adolescent substance use and changes in cognition, mental health, and future substance use risk may assist our understanding of the consequences of drug exposure during this critical window.

The effect of nicotine patches on craving in the brain: A functional MRI study on heavy smokers

BACKGROUND

Smoking is a common phenomenon and kills over 6 million people every year. Many smokers try to quit smoking by using nicotine replacement therapy (NRT). Most of the time, relapse occurs in less than six months after finishing the program of NRT. We performed a single blinded study in which our aim was to figure out what the effect of the nicotine patch is on craving in the brain of smokers deprived from smoking.

METHODS

Five heavy smokers (Fagerström Test for Nicotine Dependence ≥4) underwent a functional magnetic resonance imaging (fMRI) in 4 random conditions: smoking (S); smoking deprivation (SD); SD combined with a NP (SD + NP); SD combined with a placebo patch (SD + PP). Visual stimulation provoked craving in block design by randomly displaying images of smoking related scenes. After image preprocessing, a fixed-effect analysis was performed to compare average group activations. The Questionnaire for Smoking Urges (QSU) was obtained before and after each scan.

RESULTS

The fMRI results showed higher activation in areas involved in craving in S compared with SD + NP, SD + PP, and SD. In the SD + NP, limbic circuit and attention area were higher activated compared with SD and SD + PP. The SD + PP and SD showed higher activation in the frontal cortex and limbic system compared with S and SD + NP. Nonsmokers showed higher limbic activation compared with SD.The QSU increased significantly after the fMRI experiment in S (P = .036).The SD had higher QSU scores compared with the S before (P = .002), and also after (P = .022) the fMRI experiment. The NP showed lower scores than the SD before the experiment (P = .046).

CONCLUSION

The fMRI experiment revealed lower activity in areas associated with attention when subjects were nicotine deprived (SD + PP and SD). Areas involved with craving showed less activity when nicotine is present (S and SD + NP). The QSU showed a significant difference between SD and when nicotine is present (S and SD + NP).

A fMRI study on the impact of advertising for flavored e-cigarettes on susceptible young adults

BACKGROUND

E-cigarettes are sold in flavors such as "skittles," "strawberrylicious," and "juicy fruit," and no restrictions are in place on marketing e-cigarettes to youth. Sweets/fruits depicted in e-cigarette advertisements may increase their appeal to youth and interfere with health warnings. This study tested a brain biomarker of product preference for sweet/fruit versus tobacco flavor e-cigarettes, and whether advertising for flavors interfered with warning labels.

METHODS

Participants (N = 26) were college-age young adults who had tried an e-cigarette and were susceptible to future e-cigarette use. They viewed advertisements in fMRI for sweet/fruit and tobacco flavor e-cigarettes, menthol and regular cigarettes, and control images of sweets/fruits/mints with no tobacco product. Cue-reactivity was measured in the nucleus accumbens, a brain biomarker of product preference. Advertisements randomly contained warning labels, and recognition of health warnings was tested post-scan. Visual attention was measured using eye-tracking.

RESULTS

There was a significant effect of e-cigarette condition (sweet/tobacco/control) on nucleus accumbens activity, that was not found for cigarette condition (menthol/regular/control). Nucleus accumbens activity was greater for sweet/fruit versus tobacco flavor e-cigarette advertisements and did not differ compared with control images of sweets and fruits. Greater nucleus accumbens activity was correlated with poorer memory for health warnings.

CONCLUSIONS

These and exploratory eye-tracking findings suggest that advertising for sweet/fruit flavors may increase positive associations with e-cigarettes and/or override negative associations with tobacco, and interfere with health warnings, suggesting that one way to reduce the appeal of e-cigarettes to youth and educate youth about e-cigarette health risks is to regulate advertising for flavors.

Adolescents' behavioral and neural responses to e-cigarette advertising

Although adolescents are a group heavily targeted by the e-cigarette industry, research in cue-reactivity has not previously examined adolescents' behavioral and neural responses to e-cigarette advertising. This study addressed this gap through two experiments. In Experiment One, adult traditional cigarette smokers (n = 41) and non-smokers (n = 41) answered questions about e-cigarette and neutral advertising images. The 40 e-cigarette advertising images that most increased desire to use the product were matched to 40 neutral advertising images with similar content. In Experiment Two, the 80 advertising images selected in Experiment One were presented to adolescents (n = 30) during an functional magnetic resonance imaging brain scan. There was a range of traditional cigarette smoking across the sample with some adolescents engaging in daily smoking and others who had never smoked. Adolescents self-reported that viewing the e-cigarette advertising images increased their desire to smoke. Additionally, all participants regardless of smoking statuses showed significantly greater brain activation to e-cigarette advertisements in areas associated with cognitive control (left middle frontal gyrus), reward (right medial frontal gyrus), visual processing/attention (left lingual gyrus/fusiform gyrus, right inferior parietal lobule, left posterior cingulate, left angular gyrus) and memory (right parahippocampus, left insula). Further, an exploratory analysis showed that compared with age-matched non-smokers (n = 7), adolescent smokers (n = 7) displayed significantly greater neural activation to e-cigarette advertising images in the left inferior temporal gyrus/fusiform gyrus, compared with their responses to neutral advertising images. Overall, participants' brain responses to e-cigarette advertisements suggest a need to further investigate the long-run impact of e-cigarette advertising on adolescents.

Cue-Induced Brain Activation in Chronic Ketamine-Dependent Subjects, Cigarette Smokers, and Healthy Controls: A Task Functional Magnetic Resonance Imaging Study

BACKGROUND

Observations of drug-related cues may induce craving in drug-dependent patients, prompting compulsive drug-seeking behavior. Sexual dysfunction is common in drug users. The aim of the study was to examine regional brain activation to drug (ketamine, cigarette smoking) associated cues and natural (sexual) rewards.

METHODS

A sample of 129 [40 ketamine use smokers (KUS), 45 non-ketamine use smokers (NKUS) and 44 non-ketamine use non-smoking healthy controls (HC)] participants underwent functional magnetic resonance imaging (fMRI) while viewing ketamine use related, smoking and sexual films.

RESULTS

We found that KUS showed significant increased activation in anterior cingulate cortex and precuneus in response to ketamine cues. Ketamine users (KUS) showed lower activation in cerebellum and middle temporal cortex compared with non-ketamine users (NKUS and HC) in response to sexual cues. Smokers (KUS and NKUS) showed higher activation in the right precentral frontal cortex in response to smoking cues. Non-ketamine users (NKUS and HC) showed significantly increased activation of cerebellum and middle temporal cortex while viewing sexual cues.

CONCLUSION

These findings clearly show the engagement of distinct neural circuitry for drug-related stimuli in chronic ketamine users. While smokers (both KUS and NKUS) showed overlapping differences in activation for smoking cues, the former group showed a specific neural response to relevant (i.e., ketamine-related) cues. In particular, the heightened response in anterior cingulate cortex may have important implications for how attentionally salient such cues are in this group. Ketamine users (KUS) showed lower activation in response to sexual cues may partly reflect the neural basis of sexual dysfunction.

Altered function but not structure of the amygdala in nicotine-dependent individuals

Tobacco use disorder is frequently comorbid with emotional disorders, each exerting reciprocal influence on the other. As an important hub for emotional processing, amygdala may also play a critical role in tobacco addiction. Therefore, we aimed to investigate the volume and spontaneous activity of the amygdala in nicotine-dependent individuals and their relationships with cigarette use. A total of 84 smokers (aged 22-54 years) and 41 nonsmokers (aged 26-56 years) were enrolled in the present study. 3D-T1 weighted images and resting-state fMRI images were acquired from all participants. We used ROI-wise volume, fractional amplitude of low frequency fluctuation (fALFF) and resting-state functional connectivity (FC) to assess structural and functional changes of the amygdala in the smokers. There was no significant difference between smokers and nonsmokers on amygdala volume (p > 0.05). When compared to nonsmokers, increased fALFF in the right amygdala was observed in smokers (p = 0.024). In addition, increased FC between the left amygdala and the right precuneus and decreased FC between the right amygdala and the right orbitofrontal cortex (OFC) was found in smokers. In smokers, these amygdala measures did not correlate with any measures of cigarette use. The results revealed that the amygdala function but not volume was affected in nicotine addiction. When considering the fALFF and FC results, we propose that the OFC top-down control may regulate the amygdala activity in nicotine addicts. The pattern of amygdala-based FC in smokers revealed in our study may provide new information about the brain circuitry of tobacco dependence.

Reward-related frontostriatal activity and smoking behavior among adolescents in treatment for smoking cessation

BACKGROUND

Tobacco use is often initiated during adolescence and continued into adulthood despite desires to quit. A better understanding of the neural correlates of abstinence from smoking in adolescents may inform more effective smoking cessation interventions. Neural reward systems are implicated in tobacco use disorder, and adolescent smokers have shown reduced reward-related ventral striatal activation related to increased smoking.

METHODS

The current study evaluated nondrug reward anticipation in adolescent smokers using a monetary incentive delay task in fMRI pre- and post- smoking cessation treatment (n=14). This study tested how changes in neural responses to reward anticipation pre- to post-treatment were related to reduced smoking. An exploratory analysis in a larger sample of adolescents with only pre-treatment fMRI (n=28) evaluated how neural responses to reward anticipation were related to behavioral inhibition and behavioral activation scales.

RESULTS

Adolescent smokers showed pre- to post-treatment increases in reward anticipation-related activity in the bilateral nucleus accumbens and insula, and medial prefrontal cortex, and greater increases in reward anticipation-related activity were correlated with larger percent days of smoking abstinence during treatment.

CONCLUSIONS

These findings suggest that reduced smoking during smoking cessation treatment is associated with a "recovery of function" in frontostriatal responses to nondrug reward anticipation in adolescent smokers, although comparison with a developmental control group of adolescent nonsmokers is warranted.

Developmental toxicity of nicotine: A transdisciplinary synthesis and implications for emerging tobacco products

While the health risks associated with adult cigarette smoking have been well described, effects of nicotine exposure during periods of developmental vulnerability are often overlooked. Using MEDLINE and PubMed literature searches, books, reports and expert opinion, a transdisciplinary group of scientists reviewed human and animal research on the health effects of exposure to nicotine during pregnancy and adolescence. A synthesis of this research supports that nicotine contributes critically to adverse effects of gestational tobacco exposure, including reduced pulmonary function, auditory processing defects, impaired infant cardiorespiratory function, and may contribute to cognitive and behavioral deficits in later life. Nicotine exposure during adolescence is associated with deficits in working memory, attention, and auditory processing, as well as increased impulsivity and anxiety. Finally, recent animal studies suggest that nicotine has a priming effect that increases addiction liability for other drugs. The evidence that nicotine adversely affects fetal and adolescent development is sufficient to warrant public health measures to protect pregnant women, children, and adolescents from nicotine exposure.

Nicotine deprivation elevates neural representation of smoking-related cues in object-sensitive visual cortex: a proof of concept study

OBJECTIVE

In the current study, we use functional magnetic resonance imaging (fMRI) and multi-voxel pattern analysis (MVPA) to investigate whether tobacco addiction biases basic visual processing in favour of smoking-related images. We hypothesize that the neural representation of smoking-related stimuli in the lateral occipital complex (LOC) is elevated after a period of nicotine deprivation compared to a satiated state, but that this is not the case for object categories unrelated to smoking.

METHODS

Current smokers (≥10 cigarettes a day) underwent two fMRI scanning sessions: one after 10 h of nicotine abstinence and the other one after smoking ad libitum. Regional blood oxygenated level-dependent (BOLD) response was measured while participants were presented with 24 blocks of 8 colour-matched pictures of cigarettes, pencils or chairs. The functional data of 10 participants were analysed through a pattern classification approach.

RESULTS

In bilateral LOC clusters, the classifier was able to discriminate between patterns of activity elicited by visually similar smoking-related (cigarettes) and neutral objects (pencils) above empirically estimated chance levels only during deprivation (mean = 61.0%, chance (permutations) = 50.0%, p = .01) but not during satiation (mean = 53.5%, chance (permutations) = 49.9%, ns.). For all other stimulus contrasts, there was no difference in discriminability between the deprived and satiated conditions.

CONCLUSION

The discriminability between smoking and non-smoking visual objects was elevated in object-selective brain region LOC after a period of nicotine abstinence. This indicates that attention bias likely affects basic visual object processing.

P3 event-related potential reactivity to smoking cues: Relations with craving, tobacco dependence, and alcohol sensitivity in young adult smokers

The current study tested whether the amplitude of the P3 event-related potential (ERP) elicited by smoking cues is (a) associated with the degree of self-reported craving reactivity, and (b) moderated by degree of tobacco dependence. Because alcohol and cigarettes are frequently used together, and given recent evidence indicating that individual differences in alcohol sensitivity influence reactivity to alcohol cues, we also investigated whether alcohol sensitivity moderated neural responses to smoking cues. ERPs were recorded from young adult smokers (N = 90) while they participated in an evaluative categorization oddball task involving 3 types of targets: neutral images, smoking-related images, and images of drinking straws. Participants showing larger P3 amplitudes to smoking cues and to straw cues (relative to neutral targets) reported greater increases in craving after cue exposure. Neither smoking status (daily vs. occasional use) nor psychometric measures of tobacco dependence consistently or specifically moderated P3 reactivity to smoking cues. Lower alcohol sensitivity was associated with larger P3 to smoking cues but not comparison straw cues (relative to neutral targets). This effect was further moderated by tobacco dependence, with the combination of lower sensitivity and higher dependence associated with especially pronounced P3 reactivity to smoking cues. The findings suggest the smoking-cue elicited P3 ERP component indexes an approach-oriented incentive motivational state accompanied by a subjective sense of cigarette craving. Self-reported low sensitivity to the pharmacologic effects of alcohol may represent a marker of drug cue reactivity and therefore deserves attention as a potential moderator in smoking cue exposure studies. (PsycINFO Database Record

Functional Connectivity During Exposure to Favorite-Food, Stress, and Neutral-Relaxing Imagery Differs Between Smokers and Nonsmokers

INTRODUCTION

Tobacco-use disorder is a complex condition involving multiple brain networks and presenting with multiple behavioral correlates including changes in diet and stress. In a previous functional magnetic resonance imaging (fMRI) study of neural responses to favorite-food, stress, and neutral-relaxing imagery, smokers versus nonsmokers demonstrated blunted corticostriatal-limbic responses to favorite-food cues. Based on other recent reports of alterations in functional brain networks in smokers, the current study examined functional connectivity during exposure to favorite-food, stress, and neutral-relaxing imagery in smokers and nonsmokers, using the same dataset.

METHODS

The intrinsic connectivity distribution was measured to identify brain regions that differed in degree of functional connectivity between groups during each imagery condition. Resulting clusters were evaluated for seed-to-voxel connectivity to identify the specific connections that differed between groups during each imagery condition.

RESULTS

During exposure to favorite-food imagery, smokers versus nonsmokers showed lower connectivity in the supramarginal gyrus, and differences in connectivity between the supramarginal gyrus and the corticostriatal-limbic system. During exposure to neutral-relaxing imagery, smokers versus nonsmokers showed greater connectivity in the precuneus, and greater connectivity between the precuneus and the posterior insula and rolandic operculum. During exposure to stress imagery, smokers versus nonsmokers showed lower connectivity in the cerebellum.

CONCLUSIONS

These findings provide data-driven insights into smoking-related alterations in brain functional connectivity patterns related to appetitive, relaxing, and stressful states.

IMPLICATIONS

This study uses a data-driven approach to demonstrate that smokers and nonsmokers show differential patterns of functional connectivity during guided imagery related to personalized favorite-food, stress, and neutral-relaxing cues, in brain regions implicated in attention, reward-related, emotional, and motivational processes. For smokers, these differences in connectivity may impact appetite, stress, and relaxation, and may interfere with smoking cessation.

Neurobiological signatures associated with alcohol and drug use in the human adolescent brain

Magnetic resonance (MR) techniques provide opportunities to non-invasively characterize neurobiological milestones of adolescent brain development. Juxtaposed to the critical finalization of brain development is initiation of alcohol and substance use, and increased frequency and quantity of use, patterns that can lead to abuse and addiction. This review provides a comprehensive overview of existing MR studies of adolescent alcohol and drug users. The most common alterations reported across substance used and MR modalities are in the frontal lobe (63% of published studies). This is not surprising, given that this is the last region to reach neurobiological adulthood. Comparatively, evidence is less consistent regarding alterations in regions that mature earlier (e.g., amygdala, hippocampus), however newer techniques now permit investigations beyond regional approaches that are uncovering network-level vulnerabilities. Regardless of whether neurobiological signatures exist prior to the initiation of use, this body of work provides important direction for ongoing prospective investigations of adolescent brain development, and the significant impact of alcohol and substance use on the brain during the second decade of life.

Individual differences in brain responses to cigarette-related cues and pleasant stimuli in young smokers

BACKGROUND

Decreased sensitivity to pleasant stimuli is associated with a higher vulnerability to nicotine dependence in youths and with difficulty quitting in adult smokers. Recently, we showed that smokers showing lower brain reactivity to non-cigarette-related pleasant images than to cigarette-related ones have lower chances of achieving long-term abstinence during a quit attempt.

METHODS

We tested whether individual differences in brain responses to cigarette-related and pleasant stimuli require a long history of smoking to develop by measuring the late positive potential (LPP) to cigarette cues, emotional, and neutral stimuli in 45 young, light smokers (ages 18-25). k-means cluster analysis was used to partition smokers into two groups based on the magnitude of their LPPs.

RESULTS

Group 1 was characterized by larger LPPs to pleasant pictures than cigarette-related pictures whereas Group 2 showed the opposite pattern.

CONCLUSIONS

Our results suggest that individual differences in brain responses to cigarette-related and pleasant cues do not require a long smoking history to develop.

Neural Sensitivity to Smoking Stimuli Is Associated With Cigarette Craving in Adolescent Smokers

PURPOSE

Adolescents initiate cigarette smoking at disproportionately high rates, despite widespread knowledge of its health-compromising and long-term consequences. Psychosocial factors clearly play a role in adolescent smoking initiation, but the role of the developing adolescent brain in this behavior remains unclear. The goal of the present study was to determine whether greater neural sensitivity to smoking cues in adolescents compared to adults underlies increased proclivity toward smoking behavior and craving.

METHODS

We addressed this question in a sample of adolescent (n = 39) and adult (n = 39) smokers and nonsmokers by assessing craving in response to smoking videos that featured late adolescents/young adults while participants underwent functional magnetic resonance imaging.

RESULTS

Ventral striatal activation mediated the relationship between video-induced craving and subsequent desires to smoke following the scan in adolescent smokers only. We also found that functional coupling between striatal and cortical regions was associated with increased craving in adolescent smokers.

CONCLUSIONS

These novel results demonstrate that adolescent smokers may be more neurobiologically responsive to smoking stimuli than adults, perhaps because of ongoing ontogenetic changes in adolescents that normatively occur in frontostriatal circuitry.

Sleeping problems in Chinese illicit drug dependent subjects

BACKGROUND

Illicit drug use/dependence has been recognized as a major problem. Clinical studies demonstrate that poor sleep quality is associated with increased frequency of drug use and relapse. However, few studies have addressed the issue of sleep quality among illicit drug dependent subjects.

METHODS

This cross-sectional study explored sleep quality in drug dependent subjects in China. We studied 2178 illicit drug dependent subjects from drug rehabilitation centres in Changsha and 2236 non-drug-using subjects, all of whom completed the self-report Pittsburgh Sleep Quality Index (PSQI).

RESULTS

We found that the prevalence of sleep disturbance was much higher in drug users (68.5%, PSQI >5; specifically, 80.24% in heroin users, 54.16% in methamphetamine users and 81.98% in ketamine users with PSQI >5) than non-users (26.4%, PSQI >5). Drug users had approximately twice the sleep latency than nondrug users (37.7 minutes V.S 18.4 minutes). Although drug users and non-users reported similar sleep duration (about 7.4 hours), drug users showed poorer subjective sleep quality and habitual sleep efficiency. They reported more sleep disturbance and need for sleep medications, more daytime dysfunction and poorer subjective sleep quality compared with nondrug users. The total PSQI score positively correlated with the duration of drug use (rp = 0.164, p < 0.001). We also found a link between sleep problems and cigarette smoking, alcohol drinking, and duration of drug use.

CONCLUSIONS

Poor sleep quality is common among illicit drug dependent subjects. Long-term substance users had more sleep problems. Future research aiming at quantifying the benefits of treatment interventions should not neglect the influence of sleep problems. Gaining more insight into the impact of sleep quality on the addiction treatment could also help to target future intervention measures more effectively.

Visual cortex activation to drug cues: a meta-analysis of functional neuroimaging papers in addiction and substance abuse literature

BACKGROUND

Although the visual cortex does not typically receive much attention in addiction literature, neuroimaging studies often report significant activity in visual areas when drug users are exposed to drug cues. The purpose of this meta-analysis was to investigate the frequency with which occipital cortex activity is observed during drug cue exposure and to determine its spatial distribution.

METHODS

A comprehensive literature search was performed of human functional neuroimaging studies of drug cue-reactivity. Fifty-five studies were used to determine the frequency with which clusters of significant visual cortex activity during visual drug cues versus non-drug cues were reported. The spatial distribution of visual cortex activations was determined via activation likelihood estimation (ALE; FDR corrected, p<0.01) in a subset of these studies (n=24).

RESULTS

Eighty-six percent of studies that reported fMRI results for drug versus neutral visual cues within a substance-dependent group showed significant drug-elicited activity in the visual cortex. ALE revealed clusters in the left secondary visual cortex (BA 19) and clusters in the primary visual cortex (BA 17) that were consistently activated by drug cues.

CONCLUSIONS

These data demonstrate that the visual cortex, often overlooked in our discussions of the neural circuitry of addiction, consistently discriminates drug cues from neutral cues in substance dependent populations. While it remains unclear whether drug cue-elicited activation in occipital cortex is related to the rewarding properties of the drug and/or attentional mechanisms, these data support further exploration.

Treatment with a nicotine vaccine does not lead to changes in brain activity during smoking cue exposure or a working memory task

AIMS

To assess whether immunization attenuates nicotinic stimulation of the brain and elucidate brain and behavioural responses during exposure to smoking cues and a working memory task.

DESIGN

Randomized, placebo-controlled parallel-group, repeated-measures design.

SETTING

Maastricht University, the Netherlands.

PARTICIPANTS

Forty-eight male smokers were randomized to receive five injections with either 400 μg/ml of the 3'-aminomethylnicotine Pseudomonas aeruginosa r-Exoprotein-conjugated vaccine or placebo. Subjects were tested on two occasions, once after a nicotine challenge and once after a placebo challenge, and were asked to refrain from smoking 10 hours before testing.

MEASUREMENTS

Reaction-times and accuracies were recorded during an n-back task. Moreover, regional blood oxygenated level-dependent (BOLD) response was measured during this task and during smoking cue exposure.

FINDINGS

Greater activation was found in response to smoking cues compared to neutral cues in bilateral trans-occipital sulcus (P < 0.005); however, this effect did not survive correction for multiple comparisons. There was no difference in brain activity to smoking cues between the treatment groups and no effects of acute nicotine challenge were established. For the n-back task we found working memory load-sensitive increases in brain activity in several frontal and parietal areas (P < 0.0025). However, no effects of immunization or nicotine challenge were observed.

CONCLUSION

No significant effects of immunization on brain activity in response to a nicotine challenge were established. Therefore this vaccine is not likely to be an effective aid in smoking cessation.

The development and expression of physical nicotine dependence corresponds to structural and functional alterations in the anterior cingulate-precuneus pathway

INTRODUCTION

Perturbations in neural function provoked by a drug are thought to induce neural adaptations, which, in the absence of the drug, give rise to withdrawal symptoms. Previously published structural data from this study indicated that the progressive development of physical dependence is associated with increasing density of white matter tracts between the anterior cingulum bundle and the precuneus.

METHODS

Using functional magnetic resonance imaging, we compared 11 smokers after 11 h of abstinence from nicotine and after satiation, with 10 nonsmoking controls, using independent component analysis for brain network comparisons as well as a whole brain resting-state functional connectivity analysis using the anterior cingulate cortex as a seed.

RESULTS

Independent component analysis demonstrated increased functional connectivity in brain networks such as the default mode network associated with the withdrawal state in multiple brain regions. In seed-based analysis, smokers in the withdrawal state showed stronger functional connectivity than nonsmoking controls between the anterior cingulate cortex and the precuneus, caudate, putamen, and frontal cortex (P < 0.05). Among smokers, compared to the satiated state, nicotine withdrawal was associated with increased connectivity between the anterior cingulate cortex and the precuneus, insula, orbital frontal gyrus, superior frontal gyrus, posterior cingulate cortex, superior temporal, and inferior temporal lobe (P < 0.02). The intensity of withdrawal-induced craving correlated with the strength of connectivity between the anterior cingulate cortex and the precuneus, insula, caudate, putamen, middle cingulate gyrus, and precentral gyrus (r = 0.60-0.76; P < 0.05).

CONCLUSIONS

In concordance with our previous report that structural neural connectivity between the anterior cingulate area and the precuneus increased in proportion to the progression of physical dependence, resting-state functional connectivity in this pathway increases during nicotine withdrawal in correlation with the intensity of withdrawal-induced craving. These findings suggest that smoking triggers structural and functional neural adaptations in the brain that support withdrawal-induced craving.

Craving, cue reactivity, and stimulus control among early-stage young smokers: effects of smoking intensity and gender

INTRODUCTION

Smoking initiation usually begins in adolescence, but how and for whom nicotine dependence emerges during this period is unclear. The cue-reactivity paradigm is well suited to examine one marker of dependence: craving-related stimulus control, i.e., the ability of environmental cues to elicit craving to smoke. This study examined the effects of both level of smoking involvement (daily vs. occasional smoking) and gender on reactivity to both smoking and alcohol cues.

METHODS

Young (age range 16-20; 42% female) daily (n = 55) and occasional (n = 52) smokers were exposed to each of three counterbalanced cues: (a) in vivo smoking (e.g., sight, smell, lighting of cigarette), (b) alcohol (e.g., opening, pouring, and smell of preferred beverage), and (c) neutral cue.

RESULTS

Daily smokers exhibited higher levels of tonic (i.e., noncue-elicited) craving than did occasional smokers. Both groups showed significant increases in craving in response to cues (i.e., cue-elicited craving), with little evidence that cue-elicited craving differed between groups. Females were more cue reactive to both the alcohol and smoking cues than males, particularly for the positively reinforced aspects of smoking (i.e., hedonic craving). There were no gender × group interaction effects in response to either the alcohol or the smoking cue.

CONCLUSIONS

Findings show the presence of cue-elicited craving even among occasional smokers and are consistent with literature demonstrating heightened sensitivity to environmental cues among females. Cue-elicited craving may be one mechanism that contributes to the maintenance of smoking behavior and perhaps to the development of nicotine dependence within early stage smokers.

Cellular, molecular, and genetic substrates underlying the impact of nicotine on learning

Addiction is a chronic disorder marked by long-lasting maladaptive changes in behavior and in reward system function. However, the factors that contribute to the behavioral and biological changes that occur with addiction are complex and go beyond reward. Addiction involves changes in cognitive control and the development of disruptive drug-stimuli associations that can drive behavior. A reason for the strong influence drugs of abuse can exert on cognition may be the striking overlap between the neurobiological substrates of addiction and of learning and memory, especially areas involved in declarative memory. Declarative memories are critically involved in the formation of autobiographical memories, and the ability of drugs of abuse to alter these memories could be particularly detrimental. A key structure in this memory system is the hippocampus, which is critically involved in binding multimodal stimuli together to form complex long-term memories. While all drugs of abuse can alter hippocampal function, this review focuses on nicotine. Addiction to tobacco products is insidious, with the majority of smokers wanting to quit; yet the majority of those that attempt to quit fail. Nicotine addiction is associated with the presence of drug-context and drug-cue associations that trigger drug seeking behavior and altered cognition during periods of abstinence, which contributes to relapse. This suggests that understanding the effects of nicotine on learning and memory will advance understanding and potentially facilitate treating nicotine addiction. The following sections examine: (1) how the effects of nicotine on hippocampus-dependent learning change as nicotine administration transitions from acute to chronic and then to withdrawal from chronic treatment and the potential impact of these changes on addiction, (2) how nicotine usurps the cellular mechanisms of synaptic plasticity, (3) the physiological changes in the hippocampus that may contribute to nicotine withdrawal deficits in learning, and (4) the role of genetics and developmental stage (i.e., adolescence) in these effects.

Progressive levels of physical dependence to tobacco coincide with changes in the anterior cingulum bundle microstructure

BACKGROUND

The tobacco withdrawal syndrome indicates the development of neurophysiologic dependence. Clinical evidence indicates that neurophysiologic dependence develops through a set sequence of symptom presentation that can be assessed with a new 3-item survey measure of wanting, craving, and needing tobacco, the Level of Physical Dependence (PD). This study sought to determine if advancing neurophysiologic dependence as measured by the Level of PD correlates with characteristics of white matter structure measured by Fractional Anisotropy (FA).

METHODS

Diffusion-MRI based FA and diffusion tensor imaging probabilistic tractography were used to evaluate 11 smokers and 10 nonsmokers. FA was also examined in relation to two additional measures of dependence severity, the Hooked on Nicotine Checklist (HONC), and the Fagerström Test for Nicotine Dependence (FTND).

RESULTS

Among smokers, FA in the left anterior cingulate bundle (ACb) correlated negatively with the Level of PD (r = -0.68, p = 0.02) and HONC scores (r = -0.65, p = 0.03), but the correlation for the FTND did not reach statistical significance (r = -49, p = 0.12). With advancing Levels of PD, the density of streamlines between the ACb and precuneus increased (r = -0.67, p<0.05) and those between the ACb and white matter projecting to the superior-frontal cortex (r = -0.86, p = 0.0006) decreased significantly.

CONCLUSIONS

The correlations between neural structure and both the clinical Level of PD survey measure and the HONC suggest that the Level of PD and the HONC may reflect the microstructural integrity of white matter, as influenced by tobacco abuse. Given that the Level of PD is measuring a sequence of symptoms of neurophysiologic dependence that develops over time, the correlation between the Level of PD and neural structure suggests that these features might represent neuroplastic changes that develop over time to support the development of neurophysiologic dependence.

Neuroeconomics and adolescent substance abuse: individual differences in neural networks and delay discounting

OBJECTIVE

Many adolescents with substance use problems show poor response to evidence-based treatments. Treatment outcome has been associated with individual differences in impulsive decision making as reflected by delay discounting (DD) rates (preference for immediate rewards). Adolescents with higher rates of DD were expected to show greater neural activation in brain regions mediating impulsive/habitual behavioral choices and less activation in regions mediating reflective/executive behavioral choices.

METHOD

Thirty adolescents being treated for substance abuse completed a DD task optimized to balance choices of immediate versus delayed rewards, and a control condition accounted for activation during magnitude valuation. A group independent component analysis on functional magnetic resonance imaging time courses identified neural networks engaged during DD. Network activity was correlated with individual differences in discounting rate.

RESULTS

Higher discounting rates were associated with diminished engagement of an executive attention control network involving the dorsolateral prefrontal cortex, dorsomedial prefrontal cortex, inferior parietal cortex, cingulate cortex, and precuneus. Higher discounting rates also were associated with less deactivation in a "bottom-up" reward valuation network involving the amygdala, hippocampus, insula, and ventromedial prefrontal cortex. These 2 networks were significantly negatively correlated.

CONCLUSIONS

Results support relations between competing executive and reward valuation neural networks and temporal decision making, an important, potentially modifiable risk factor relevant for the prevention and treatment of adolescent substance abuse. Clinical trial registration information-The Neuroeconomics of Behavioral Therapies for Adolescent Substance Abuse, http://clinicaltrials.gov/, NCT01093898.

A developmental perspective on neuroeconomic mechanisms of contingency management

This paper provides a developmental overview of relevant theory and research on delay discounting and neuroeconomics, and their implications for contingency management (CM) approaches to treatment. Recent advances in the neuroscience of decision making have the potential to inform treatment development for adolescent substance use in general, and CM treatments in particular. CM interventions may be informed by research on delay discounting, a type of decision making that reflects how individuals value immediate versus delayed rewards. Delay discounting reliably distinguishes substance abusers from nonabusers and is a significant predictor of individual differences in response to substance use treatments. Discounting may also be important in predicting response to CM, as CM attempts to directly influence this decision-making process, shifting the preference from the immediate rewards of use to delayed rewards for choosing not to use. Multiple neural processes underlie decision making, and those processes have implications for adolescent substance abuse. There are significant neurodevelopmental processes that differentiate adolescents from adults. These processes are implicated in delay discounting, suggesting that adolescence may reflect a period of plasticity in temporal decision making. Understanding the neural mechanisms of delay discounting has led to promising working memory interventions directly targeting the executive functions that underlie individual choices. These interventions may be particularly helpful in combination with CM interventions that offer immediate rewards for brief periods of abstinence, and may show particular benefit in adolescence due to the heightened neural plasticity of systems that underlie temporal discounting in adolescence.

Nicotine metabolism and addiction among adolescent smokers

AIMS

The purpose of this study was to determine the association between the nicotine metabolic rate and smoking behavior, including addiction, in adolescent smokers.

DESIGN

Baseline data from a prospective study of adolescent smoking behaviors and nicotine metabolism.

SETTING

The setting was an out-patient university hospital in San Francisco.

PARTICIPANTS

Adolescent smokers (n = 164) aged 13-17 years old.

MEASUREMENTS

Participants completed self-report measures of smoking behavior and nicotine dependence (modified Fagerström Tolerance Questionnaire: mFTQ). The nicotine metabolite ratio (NMR), a phenotypic marker of the rate of nicotine metabolism, was calculated using the ratio of concentrations of deuterium-labeled 3'-hydroxycotinine to cotinine-d(4) .

FINDINGS

Participants reported smoking a mean of 2.86 cigarettes per day (CPD) [median = 1.78, standard deviation (SD) = 3.35] for 1.37 years (median = 1.0, SD = 1.36). Results from multivariate analyses accounting for age, race/ethnicity, gender and duration of smoking indicated that slower metabolizers smoked more CPD than faster metabolizers (the NMR was inversely related to CPD; P = 0.02). Slower metabolizers also showed greater dependence on the mFTQ (NMR was negatively associated with the mFTQ; P = 0.02).

CONCLUSIONS

In adolescence, slower clearance of nicotine may be associated with greater levels of addiction, perhaps mediated by a greater number of cigarettes smoked.

Neuroadaptation in nicotine addiction: update on the sensitization-homeostasis model

The role of neuronal plasticity in supporting the addictive state has generated much research and some conceptual theories. One such theory, the sensitization-homeostasis (SH) model, postulates that nicotine suppresses craving circuits, and this triggers the development of homeostatic adaptations that autonomously support craving. Based on clinical studies, the SH model predicts the existence of three distinct forms of neuroplasticity that are responsible for withdrawal, tolerance and the resolution of withdrawal. Over the past decade, many controversial aspects of the SH model have become well established by the literature, while some details have been disproven. Here we update the model based on new studies showing that nicotine dependence develops through a set sequence of symptoms in all smokers, and that the latency to withdrawal, the time it takes for withdrawal symptoms to appear during abstinence, is initially very long but shortens by several orders of magnitude over time. We conclude by outlining directions for future research based on the updated model, and commenting on how new experimental studies can gain from the framework put forth in the SH model.

Cue-elicited craving in heroin addicts at different abstinent time: an fMRI pilot study

OBJECTIVE

We evaluated the effect of short-term and long-term heroin abstinence on brain responses to heroin-related cues using functional magnetic resonance imaging (fMRI).

METHODS

Eighteen male heroin addicts following short-term abstinence and 19 male heroin addicts following long-term abstinence underwent fMRI scanning while viewing heroin-related and neutral images. Cue-elicited craving and withdrawal symptoms in the subjects were measured.

RESULTS

Following short-term abstinence, greater activation was found in response to heroin cues compared to neutral cues in bilateral temporal, occipital, posterior cingulate, anterior cingulate, thalamus, cerebellum, and left hippocampus. In contrast, activations in bilateral temporal and occipital and deactivations in bilateral frontal, bilateral parietal, left posterior cingulate, insula, thalamus, dorsal striatum, and bilateral cerebellum were observed following long-term abstinence. Direct comparisons between conditions showed greater brain reactivity in response to smoking cues following short-term abstinence. In addition, short-term abstinence had more serious withdrawal symptoms than the long-term.

CONCLUSION

The present findings indicate that compared to short-term, long-term abstinence manifests less serious withdrawal symptoms and significantly decreases neural responses to heroin-related cues in brain regions subserving visual sensory processing, attention, memory, and action planning. These findings suggest that long-term abstinence can decrease the salience of conditioned cues, thereby reducing the risk of relapses. The study's limitations are noted.

[Adolescent daily smoking, negative mood-states and the role of family communication]

OBJECTIVE

To determine whether negative mood states constitute a risk factor for daily smoking during adolescence, and to specify the role of familial factors in the association between the two variables.

METHODS

Cross-sectional study of a representative sample (second wave, Panel of Families and Childhood) of Catalan adolescents between 14 and 18 years of age. Six logistic regression models were used for girls (n = 1,442) and six for boys (n =1,100) in order to determine whether negative mood states constitute a risk factor for daily cigarette consumption, and to what extent this effect is attributable to familial factors.

RESULTS

The prevalence of daily smoking at ages 17-18 is 3.8% for girls and 3.6 for boys. Feelings of sadness constitute a risk factor for daily cigarette consumption (odds ratio [OR] = 1.633), and communication with the father cancels out this effect. Parental pressure is a risk factor for daily smoking in both sexes (girls, OR = 2.064; boys, OR = 1.784). When parental communication is controlled for, this effect is reduced but not canceled out. Living in a reconstituted family is a risk factor for daily cigarette consumption among boys (OR = 2.988).

CONCLUSIONS

Intergenerational communication decreases the risk of daily tobacco use among adolescents independently of their mood state. Anti-smoking interventions designed in accordance with these findings may be more effective.

Neural substrates of smoking cue reactivity: a meta-analysis of fMRI studies

Reactivity to smoking-related cues may be an important factor that precipitates relapse in smokers who are trying to quit. The neurobiology of smoking cue reactivity has been investigated in several fMRI studies. We combined the results of these studies using activation likelihood estimation, a meta-analytic technique for fMRI data. Results of the meta-analysis indicated that smoking cues reliably evoke larger fMRI responses than neutral cues in the extended visual system, precuneus, posterior cingulate gyrus, anterior cingulate gyrus, dorsal and medial prefrontal cortex, insula, and dorsal striatum. Subtraction meta-analyses revealed that parts of the extended visual system and dorsal prefrontal cortex are more reliably responsive to smoking cues in deprived smokers than in non-deprived smokers, and that short-duration cues presented in event-related designs produce larger responses in the extended visual system than long-duration cues presented in blocked designs. The areas that were found to be responsive to smoking cues agree with theories of the neurobiology of cue reactivity, with two exceptions. First, there was a reliable cue reactivity effect in the precuneus, which is not typically considered a brain region important to addiction. Second, we found no significant effect in the nucleus accumbens, an area that plays a critical role in addiction, but this effect may have been due to technical difficulties associated with measuring fMRI data in that region. The results of this meta-analysis suggest that the extended visual system should receive more attention in future studies of smoking cue reactivity.

Functional neuroimaging studies in addiction: multisensory drug stimuli and neural cue reactivity

Neuroimaging studies on cue reactivity have substantially contributed to the understanding of addiction. In the majority of studies drug cues were presented in the visual modality. However, exposure to conditioned cues in real life occurs often simultaneously in more than one sensory modality. Therefore, multisensory cues should elicit cue reactivity more consistently than unisensory stimuli and increase the ecological validity and the reliability of brain activation measurements. This review includes the data from 44 whole-brain functional neuroimaging studies with a total of 1168 subjects (812 patients and 356 controls). Correlations between neural cue reactivity and clinical covariates such as craving have been reported significantly more often for multisensory than unisensory cues in the motor cortex, insula and posterior cingulate cortex. Thus, multisensory drug cues are particularly effective in revealing brain-behavior relationships in neurocircuits of addiction responsible for motivation, craving awareness and self-related processing.

Do brain responses to emotional images and cigarette cues differ? An fMRI study in smokers

Chronic smoking is thought to cause changes in brain reward systems that result in overvaluation of cigarette-related stimuli and undervaluation of natural rewards. We tested the hypotheses that, in smokers, brain circuits involved in emotional processing: (i) would be more active during exposure to cigarette-related than neutral pictures; and (ii) would be less active to pleasant compared with cigarette-related pictures, suggesting a devaluation of intrinsically pleasant stimuli. We obtained whole-brain blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging data from 35 smokers during the presentation of pleasant (erotica and romance), unpleasant (mutilations and sad), neutral, and cigarette-related pictures. Whole-brain analyses showed significantly larger BOLD responses during presentation of cigarette-related pictures relative to neutral ones within the secondary visual areas, the cingulate gyrus, the frontal gyrus, the dorsal striatum, and the left insula. BOLD responses to erotic pictures exceeded responses to cigarette-related pictures in all clusters except the insula. Within the left insula we observed larger BOLD responses to cigarette-related pictures than to all other picture categories. By including intrinsically pleasant and unpleasant pictures in addition to neutral ones, we were able to conclude that the presentation of cigarette-related pictures activates brain areas supporting emotional processes, but we did not find evidence of overall reduced activation of the brain reward systems in the presence of intrinsically pleasant stimuli.

Development of the motivational system during adolescence, and its sensitivity to disruption by nicotine

The brain continues to develop during adolescence, and exposure to exogenous substances such as nicotine can exert long-lasting adaptations during this vulnerable period. In order to fully understand how nicotine affects the adolescent brain it is important to understand normal adolescent brain development. This review summarizes human and animal data on brain development, with emphasis on the prefrontal cortex, for its important function in executive control over behavior. Moreover, we discuss how nicotine exposure during adolescence can disrupt brain development bearing long-term consequences on executive cognitive function in adulthood.

Adolescent smokers show decreased brain responses to pleasurable food images compared with nonsmokers

INTRODUCTION

Nicotine acts on the mesocorticolimbic circuits of the brain leading to the release of dopamine. Repeated elevations of dopamine in the brain may cause smokers to become less sensitive to "natural reinforcers." To test the theory that adolescents with low nicotine exposure may already have decreased activation when exposed to a natural reinforcer, we looked at the effect of visual cues representing "pleasurable" food on light adolescent smokers compared with nonsmokers.

METHODS

Twelve adolescent light smokers (aged 13-17 years, smoked 1-5 cigarettes/day) and 12 nonsmokers (aged 13-17 years, never smoked a cigarette) from the San Francisco Bay Area underwent functional magnetic resonance imaging scanning. During scanning, they viewed blocks of photographic images representing pleasurable foods (sweet, high fat, and salty foods) and control cues.

RESULTS

Smokers reported smoking a mean of 3.6 cigarettes/day. There was no difference in body mass index between groups (24.1 vs. 24.0, respectively, p = .99). Food images elicited greater activations in nonsmokers in multiple areas including the insula (T = 4.38, p < .001), inferior frontal region (T = 5.12, p < .001), and rolandic operculum (T = 6.18, p < .001). There were no regions where smokers demonstrated greater blood oxygenation level-dependent activations compared with nonsmokers when viewing food versus neutral images.

CONCLUSIONS

The finding of decreased activation to pleasurable food among adolescent light smokers supports the theory that these adolescents are displaying decreased sensitivity to at least one natural reinforcer. This also supports the theory that nicotine may affect the brain early in the trajectory of smoking, thus underscoring the need for early intervention among adolescent smokers.