Neural correlates of response inhibition and cigarette smoking in late adolescence

FDA cigarette warning labels lower craving and elicit frontoinsular activation in adolescent smokers

Cigarette smoking is an economically and epidemiologically expensive public health concern. Most adult smokers become addicted during adolescence, rendering it a crucial period for prevention and intervention. Although litigation claims have delayed implementation, graphic warning labels proposed by the U.S. Food and Drug Administration (FDA) may be a promising way to achieve this goal. We aimed to determine the efficacy of the labels in reducing in-scanner craving and to characterize the neurobiological responses in adolescent and adult smokers and non-smokers. While undergoing functional magnetic resonance imaging, thirty-nine 13- to 18-year-old adolescent and forty-one 25- to 30-year-old adult smokers and non-smokers rated their desire to smoke when presented with emotionally graphic warning labels and comparison non-graphic labels. Compared with adult smokers, adolescent smokers exhibited greater craving reduction in response to the warning labels. Although smokers evinced overall blunted recruitment of insula and dorsolateral prefrontal cortex (DLPFC) relative to non-smokers, an effect that was stronger in adolescent smokers, parametrically increasing activation of these regions was associated with greater craving reduction. Functional connectivity analyses suggest that greater DLPFC regulation of limbic regions predicted cigarette craving. These data underscore a prominent role of frontoinsular circuitry in predicting the efficacy of FDA graphic warning labels in craving reduction in adult and adolescent smokers.

Successful smoking cessation is associated with prefrontal cortical function during a Stroop task: A preliminary study

Although many smokers try to quit, relatively few are successful in their attempts. Here we investigated whether the ability to quit smoking is related to behavioral and neural measures of cognitive control. A functional magnetic resonance imaging study with a counting Stroop task was used to measure cognitive control in ex-smokers (N=10) who had successfully quit smoking and smokers (N=10) who continuously failed to quit smoking. Behavioral results showed a significant Stroop effect in ex-smokers and smokers. Ex-smokers exhibited less Stroop interference, indicating superior cognitive control compared with smokers. Furthermore, when incongruent trials were contrasted with congruent trials, ex-smokers showed stronger BOLD activity than smokers in the right superior frontal gyrus and anterior cingulate cortex. Although the present study does not permit us to draw strong conclusions regarding causality, the results suggest that successful smoking cessation may be mediated by superior cognitive control.

Emotion regulation in heavy smokers: experiential, expressive and physiological consequences of cognitive reappraisal

Emotion regulation dysfunctions are assumed to contribute to the development of tobacco addiction and relapses among smokers attempting to quit. To further examine this hypothesis, the present study compared heavy smokers with non-smokers (NS) in a reappraisal task. Specifically, we investigated whether non-deprived smokers (NDS) and deprived smokers (DS) differ from non-smokers in cognitive emotion regulation and whether there is an association between the outcome of emotion regulation and the cigarette craving. Sixty-five participants (23 non-smokers, 22 NDS, and 20 DS) were instructed to down-regulate emotions by reappraising negative or positive pictorial scenarios. Self-ratings of valence, arousal, and cigarette craving as well as facial electromyography and electroencephalograph activities were measured. Ratings, facial electromyography, and electroencephalograph data indicated that both NDS and DS performed comparably to nonsmokers in regulating emotional responses via reappraisal, irrespective of the valence of pictorial stimuli. Interestingly, changes in cigarette craving were positively associated with regulation of emotional arousal irrespective of emotional valence. These results suggest that heavy smokers are capable to regulate emotion via deliberate reappraisal and smokers’ cigarette craving is associated with emotional arousal rather than emotional valence. This study provides preliminary support for the therapeutic use of reappraisal to replace maladaptive emotion-regulation strategies in nicotine addicts.

Adolescent nicotine induces persisting changes in development of neural connectivity

Adolescent nicotine induces persisting changes in development of neural connectivity. A large number of brain changes occur during adolescence as the CNS matures. These changes suggest that the adolescent brain may still be susceptible to developmental alterations by substances which impact its growth. Here we review recent studies on adolescent nicotine which show that the adolescent brain is differentially sensitive to nicotine-induced alterations in dendritic elaboration, in several brain areas associated with processing reinforcement and emotion, specifically including nucleus accumbens, medial prefrontal cortex, basolateral amygdala, bed nucleus of the stria terminalis, and dentate gyrus. Both sensitivity to nicotine, and specific areas responding to nicotine, differ between adolescent and adult rats, and dendritic changes in response to adolescent nicotine persist into adulthood. Areas sensitive to, and not sensitive to, structural remodeling induced by adolescent nicotine suggest that the remodeling generally corresponds to the extended amygdala. Evidence suggests that dendritic remodeling is accompanied by persisting changes in synaptic connectivity. Modeling, electrophysiological, neurochemical, and behavioral data are consistent with the implication of our anatomical studies showing that adolescent nicotine induces persisting changes in neural connectivity. Emerging data thus suggest that early adolescence is a period when nicotine consumption, presumably mediated by nicotine-elicited changes in patterns of synaptic activity, can sculpt late brain development, with consequent effects on synaptic interconnection patterns and behavior regulation. Adolescent nicotine may induce a more addiction-prone phenotype, and the structures altered by nicotine also subserve some emotional and cognitive functions, which may also be altered. We suggest that dendritic elaboration and associated changes are mediated by activity-dependent synaptogenesis, acting in part through D1DR receptors, in a network activated by nicotine. The adolescent nicotine effects reviewed here suggest that modification of late CNS development constitutes a hazard of adolescent nicotine use.

Reduced frontal cortical thickness and increased caudate volume within fronto-striatal circuits in young adult smokers

BACKGROUND

Smoking during early adulthood results in neurophysiological and brain structural changes that may promote nicotine dependence later in life. Previous studies have revealed the important roles of fronto-striatal circuits in the pathology of nicotine dependence; however, few studies have focused on both cortical thickness and subcortical striatal volume differences between young adult smokers and nonsmokers.

METHODS

Twenty-seven young male adult smokers and 22 age-, education- and gender-matched nonsmokers were recruited in the present study. The cortical thickness and striatal volume differences of young adult smokers and age-matched nonsmokers were investigated in the present study and then correlated with pack-years and Fagerström Test for Nicotine Dependence (FTND).

RESULTS

The following results were obtained: (1) young adult smokers showed significant cortical thinning in the frontal cortex (left caudal anterior cingulate cortex (ACC), right lateral orbitofrontal cortex (OFC)), left insula, left middle temporal gyrus, right inferior parietal lobule, and right parahippocampus; (2) in regards to subcortical striatal volume, the volume of the right caudate was larger in young adult smokers than nonsmokers; and (3) the cortical thickness of the right dorsolateral prefrontal cortex (DLPFC) and OFC were associated with nicotine dependence severity (FTND) and cumulative amount of nicotine intake (pack-years) in smokers, respectively.

CONCLUSIONS

This study revealed reduced frontal cortical thickness and increased caudate volume in the fronto-striatal circuits in young adult smokers compared to nonsmokers. These deficits suggest an imbalance between cognitive control (reduced protection factors) and reward drive behaviours (increased risk factors) associated with nicotine addiction and relapse.

Alcohol and tobacco use in youth with and without chronic pain

OBJECTIVE

To compare rates of alcohol and tobacco use in youth with and without chronic pain and to identify risk factors for use.

METHODS

Participants included 186 youth (95 mixed chronic pain; 91 without chronic pain; 12-18 years old) who reported current alcohol and tobacco use, pain intensity, activity limitations, loneliness, and depressive symptoms.

RESULTS

Adolescents with chronic pain were less likely to use alcohol compared with adolescents without chronic pain (7.4% vs. 22%), and as likely to use tobacco (9% vs. 8%). Across groups, youth with higher depressive symptoms, less loneliness, and fewer activity limitations were more likely to endorse alcohol and tobacco use. Exploratory analyses revealed that risk factors for substance use differed among youth with and without chronic pain.

CONCLUSIONS

Chronic pain may not increase risk for tobacco and alcohol use in adolescents. Research is needed to understand use of other substances in this medically vulnerable population.

Deficits in behavioural inhibition in substance abuse and addiction: a meta-analysis

AIMS

Deficits in behavioural inhibitory control are attracting increasing attention as a factor behind the development and maintenance of substance dependence. However, evidence for such a deficit is varied in the literature. Here, we synthesised published results to determine whether inhibitory ability is reliably impaired in substance users compared to controls.

METHODS

The meta-analysis used fixed-effects models to integrate results from 97 studies that compared groups with heavy substance use or addiction-like behaviours with healthy control participants on two experimental paradigms commonly used to assess response inhibition: the Go/NoGo task, and the Stop-Signal Task (SST). The primary measures of interest were commission errors to NoGo stimuli and stop-signal reaction time in the SST. Additionally, we examined omission errors to Go stimuli, and reaction time in both tasks. Because inhibition is more difficult when inhibition is required infrequently, we considered papers with rare and equiprobable NoGo stimuli separately.

RESULTS

Inhibitory deficits were apparent for heavy use/dependence on cocaine, MDMA, methamphetamine, tobacco, and alcohol (and, to a lesser extent, non-dependent heavy drinkers), and in pathological gamblers. On the other hand, no evidence for an inhibitory deficit was observed for opioids or cannabis, and contradictory evidence was observed for internet addiction.

CONCLUSIONS

The results are generally consistent with the view that substance use disorders and addiction-like behavioural disorders are associated with impairments in inhibitory control. Implications for treatment of substance use are discussed, along with suggestions for future research arising from the limitations of the extant literature.

Recent Translational Findings on Impulsivity in Relation to Drug Abuse

Impulsive behavior is strongly implicated in drug abuse, as both a cause and a consequence of drug use. To understand how impulsive behaviors lead to and result from drug use, translational evidence from both human and non-human animal studies is needed. Here, we review recent (2009 or later) studies that have investigated two major components of impulsive behavior, inhibitory control and impulsive choice, across preclinical and clinical studies. We concentrate on the stop-signal task as the measure of inhibitory control and delay discounting as the measure of impulsive choice. Consistent with previous reports, recent studies show greater impulsive behavior in drug users compared with non-users. Additionally, new evidence supports the prospective role of impulsive behavior in drug abuse, and has begun to identify the neurobiological mechanisms underlying impulsive behavior. We focus on the commonalities and differences in findings between preclinical and clinical studies, and suggest future directions for translational research.

Dissociated effects of anticipating smoking versus monetary reward in the caudate as a function of smoking abstinence

BACKGROUND

Theories of addiction suggest that chronic smoking may be associated with both hypersensitivity to smoking and related cues and hyposensitivity to alternative reinforcers. However, neural responses to smoking and nonsmoking rewards are rarely evaluated within the same paradigm, leaving the extent to which both processes operate simultaneously uncertain. Behavioral evidence and theoretical models suggest that dysregulated reward processing may be more pronounced during deprivation from nicotine, but neuroimaging evidence on the effects of deprivation on reward processing is limited. The current study examined the impact of deprivation from smoking on neural processing of both smoking and monetary rewards.

METHODS

Two separate functional magnetic resonance imaging scans were performed in 38 daily smokers, one after smoking without restriction and one following 24 hours of abstinence. A rewarded guessing task was conducted during each scan to evaluate striatal blood oxygen level-dependent response during anticipation of both smoking and monetary rewards.

RESULTS

A significant reward type by abstinence interaction was observed in the bilateral caudate and medial prefrontal cortex during reward anticipation. The blood oxygen level-dependent response to anticipation of smoking reward was significantly higher and anticipation of monetary rewards was significantly lower during abstinence compared with nonabstinence. Attenuation of monetary reward-related activation during abstinence was significantly correlated with abstinence-induced increases in craving and withdrawal.

CONCLUSIONS

These results provide the first direct evidence of dissociated effects of smoking versus monetary rewards as a function of abstinence. The findings suggest an important neural pathway that may underlie the choice to smoke in lieu of alternative reinforcement during a quit attempt.

Present simple and continuous: emergence of self-regulation and contextual sophistication in adolescent decision-making

Sophisticated, intentional decision-making is a hallmark of mature, self-aware behaviour. Although neural, psychological, interpersonal, and socioeconomic elements that contribute to such adaptive, foresighted behaviour mature and/or change throughout the life-span, here we concentrate on relevant maturational processes that take place during adolescence, a period of disproportionate developmental opportunity and risk. A brief, eclectic overview is presented of recent evidence, new challenges, and current thinking on the fundamental mechanisms that mature throughout adolescence to support adaptive, self-controlled decision-making. This is followed by a proposal for the putative contribution of frontostriatal mechanisms to the moment-to-moment assembly of evaluative heuristics that mediate increased decision-making sophistication, promoting the maturation of self-regulated behaviour through adolescence and young adulthood.

Relationship between frequency and intensity of cigarette smoking and TTFC/C among students of the GYTS in select countries, 2007-2009

BACKGROUND

This study assessed the construct validity of a measure of nicotine dependence that was used in the Global Youth Tobacco Survey (GYTS).

METHODS

Using 2007-2009 data from the GYTS, subjects from 6 countries were used to assess current smokers' odds of reporting time to first cigarette or craving positive (TTFC/C+) by the number of cigarette smoking days per month (DPM) and the number of cigarettes smoked per day (CPD).

RESULTS

The percentage of GYTS smokers who reported TTFC/C+ ranged from 58.0% to 69.7%. Compared with students who smoked on 1-2 DPM, those who smoked on 3-9 DPM had 3 times the adjusted odds of reporting TTFC/C+. The adjusted odds of reporting TTFC/C+ were 3 to 7 times higher among those who smoked 10-29 DPM and 6 to 20 times higher among daily smokers. Similarly, the adjusted odds of TTFC/C+ were 3-6 times higher among those who smoked 2-5 CPD and 6 to 20 times higher among those who smoked >6 CPD, compared to those who smoked <1 CPD.

CONCLUSION

Associations of TTFC/C+ prevalence with both frequency and intensity of cigarette smoking provide a construct validation of the GYTS question used to assess respondents' TTFC/C status.

Cigarette exposure, dependence, and craving are related to insula thickness in young adult smokers

The age period spanning late adolescence to emergent adulthood is associated with the highest prevalence of cigarette smoking in the United States, and is also a time of continued brain development. Nonetheless, although prior research has shown group differences in brain structure associated with smoking status in adults, few studies have examined how smoking and associated behavioral states relate to brain structure in this age group. Neuroimaging and lesion studies have suggested that the insula, a cortical region that integrates heterogeneous signals about internal states and contributes to executive functions, plays an important role in cigarette smoking behavior. Using high-resolution structural magnetic resonance imaging, we therefore measured cortical thickness of the insula in 18 smokers and 24 nonsmokers between the ages of 16 and 21 years. There were no group differences in insula thickness, but cigarette exposure (pack-years) was negatively associated with thickness in right insula. Cigarette dependence and the urge to smoke were negatively related to cortical thickness in the right ventral anterior insula. Although the results do not demonstrate causation, they do suggest that there are effects of cigarette exposure on brain structure in young smokers, with a relatively short smoking history. It is possible that changes in the brain due to prolonged exposure or to the progression of dependence lead to more extensive structural changes, manifested in the reported group differences between adult smokers and nonsmokers. Structural integrity of the insula may have implications for predicting long-term cigarette smoking and problems with other substance abuse in this population.

A functional network perspective on response inhibition and attentional control

Inferior frontal cortex (IFC) modules that inhibit dominant behaviours are a popular feature in theories of cognitive dysfunction. However, the paradigms on which these theories are based fail to distinguish between inhibitory and non-inhibitory cognitive demands. Here we use four novel fMRI variants of the classic stop-signal task to test whether the IFC houses unique inhibitory modules. Our results demonstrate that IFC sub-regions are not functionally unique in their sensitivities to inhibitory cognitive demands, but instead form components of spatially distributed networks. These networks are most strongly activated when infrequent stimuli are being processed, regardless of behavioural inhibitory demands, and when novel tasks are being acquired, as opposed to when routine responses must be suppressed. We propose that there are no inhibitory modules within the frontal lobes and that behavioural inhibition is an emergent property of spatially distributed functional networks, each of which supports a broader class of cognitive demands.

The right inferior frontal cortex has long been thought to house a neural module that inhibits dominant behaviours. Using brain imaging, Erika-Florence et al. demonstrate that this inhibition is in fact an emergent property of multiple neural networks that support broader classes of cognitive processes.

Systematic review of ERP and fMRI studies investigating inhibitory control and error processing in people with substance dependence and behavioural addictions

BACKGROUND

Several current theories emphasize the role of cognitive control in addiction. The present review evaluates neural deficits in the domains of inhibitory control and error processing in individuals with substance dependence and in those showing excessive addiction-like behaviours. The combined evaluation of event-related potential (ERP) and functional magnetic resonance imaging (fMRI) findings in the present review offers unique information on neural deficits in addicted individuals.

METHODS

We selected 19 ERP and 22 fMRI studies using stop-signal, go/no-go or Flanker paradigms based on a search of PubMed and Embase.

RESULTS

The most consistent findings in addicted individuals relative to healthy controls were lower N2, error-related negativity and error positivity amplitudes as well as hypoactivation in the anterior cingulate cortex (ACC), inferior frontal gyrus and dorsolateral prefrontal cortex. These neural deficits, however, were not always associated with impaired task performance. With regard to behavioural addictions, some evidence has been found for similar neural deficits; however, studies are scarce and results are not yet conclusive. Differences among the major classes of substances of abuse were identified and involve stronger neural responses to errors in individuals with alcohol dependence versus weaker neural responses to errors in other substance-dependent populations.

LIMITATIONS

Task design and analysis techniques vary across studies, thereby reducing comparability among studies and the potential of clinical use of these measures.

CONCLUSION

Current addiction theories were supported by identifying consistent abnormalities in prefrontal brain function in individuals with addiction. An integrative model is proposed, suggesting that neural deficits in the dorsal ACC may constitute a hallmark neurocognitive deficit under lying addictive behaviours, such as loss of control.

Genetic risk for nicotine dependence in the cholinergic system and activation of the brain reward system in healthy adolescents

Genetic variation in a genomic region on chromosome 15q25.1, which encodes the alpha5, alpha3, and beta4 subunits of the cholinergic nicotinic receptor genes, confers risk to smoking and nicotine dependence (ND). Neural reward-related responses have previously been identified as important factors in the development of drug dependence involving ND. Applying an imaging genetics approach in two cohorts (N=487; N=478) of healthy non-smoking adolescents, we aimed to elucidate the impact of genome-wide significant smoking-associated variants in the CHRNA5-CHRNA3-CHRNB4 gene cluster on reward-related neural responses in central regions such as the striatum, orbitofrontal and anterior cingulate cortex (ACC), and personality traits related to addiction. In both samples, carriers of the rs578776 GG compared with AG/AA genotype showed a significantly lower neural response to reward outcomes in the right ventral and dorsal ACC but not the striatum or the orbitofrontal cortex. Rs578776 was unrelated to neural reward anticipation or reward magnitude. Significantly higher scores of anxiety sensitivity in GG compared with AG/AA carriers were found only in sample 1. Associations with other personality traits were not observed. Our findings suggest that the rs578776 risk variant influences susceptibility to ND by dampening the response of the ACC to reward feedback, without recruiting the striatum or orbitofrontal cortex during feedback or anticipation. Thus, it seems to have a major role in the processing of and behavioral adaptation to changing reward outcomes.

Greater risk sensitivity of dorsolateral prefrontal cortex in young smokers than in nonsmokers

RATIONALE

Despite a national reduction in the prevalence of cigarette smoking, ~19% of the adult US population persists in this behavior, with the highest prevalence among 18-25-year-olds. Given that the choice to smoke imposes a known health risk, clarification of brain function related to decision-making, particularly involving risk-taking, in smokers may inform prevention and smoking cessation strategies.

OBJECTIVES

This study aimed to compare brain function related to decision-making in young smokers and nonsmokers.

METHODS

The Balloon Analogue Risk Task (BART) is a computerized risky decision-making task in which participants pump virtual balloons, each pump associated with an incremental increase in potential payoff on a given trial but also with greater risk of balloon explosion and loss of payoff. We used this task to compare brain activation associated with risky decision-making in smokers (n = 18) and nonsmokers (n = 25), while they performed the BART during functional magnetic resonance imaging (fMRI). The participants were young men and women, 17-21 years of age.

RESULTS

Risk level (number of pumps) modulated brain activation in the right dorsolateral and ventrolateral prefrontal cortices more in smokers than in nonsmokers, and smoking severity (Heaviness of Smoking Index) was positively related to this modulation in an adjacent frontal region.

CONCLUSIONS

Given evidence for involvement of the right dorsolateral and ventrolateral prefrontal cortices in inhibitory control, these findings suggest that young smokers have a different contribution of prefrontal cortical substrates to risky decision-making than nonsmokers. Future studies are warranted to determine whether the observed neurobiological differences precede or result from smoking.

An exploratory pilot study of the relationship between neural correlates of cognitive control and reduction in cigarette use among treatment-seeking adolescent smokers

Despite high rates of tobacco use during adolescence, few empirically validated smoking cessation strategies exist for adolescent smokers. Developing an understanding of the neural underpinnings of cognitive control processes in adolescent smokers, and their relationship to quit behaviors, may help advance the development of enhanced behavioral and pharmacological therapies. The current pilot study explored the relationship between brain responses during performance of the Stroop color-word interference task and reduction in tobacco use (as measured by changes in cotinine levels) in treatment-seeking adolescent smokers participating in a high school-based smoking-cessation program. Eleven adolescent daily smokers participated in a prequit session during which neural activity in response to congruent and incongruent events in a Stroop task was examined using functional MRI (fMRI). Changes in urine cotinine levels from prequit baseline to end of treatment were calculated and correlated with brain activity. Adolescents with greater activation in the inferior frontal gyrus, insula, thalamus, and anterior cingulate had greater reductions in cotinine levels. The preliminary observation of a relationship between treatment outcome and neural correlates of cognitive control prior to treatment onset provides insight into individual differences in adolescent brain function that might relate importantly to treatment outcome.

Fronto-striatal functional connectivity during response inhibition in alcohol dependence

Poor response inhibition has been implicated in the development of alcohol dependence, yet little is known about how neural pathways underlying cognitive control are affected in this disorder. Moreover, endogenous opioid levels may impact the functionality of inhibitory control pathways. This study investigated the relationship between alcohol dependence severity and functional connectivity of fronto-striatal networks during response inhibition in an alcohol-dependent sample. A secondary aim of this study was to test the moderating effect of a functional polymorphism (A118G) of the μ-opioid receptor (OPRM1) gene. Twenty individuals with alcohol dependence (six females; 90% Caucasian; mean age = 29.4) who were prospectively genotyped on the OPRM1 gene underwent blood oxygen level-dependent functional magnetic resonance imaging while performing a Stop-Signal Task. The relationship between alcohol dependence severity and functional connectivity within fronto-striatal networks important for response inhibition was assessed using psychophysiological interaction analyses. Analyses revealed greater alcohol dependence severity was associated with weaker functional connectivity between the putamen and prefrontal regions (e.g. the anterior insula, anterior cingulate and medial prefrontal cortex) during response inhibition. Furthermore, the OPRM1 genotype was associated with differential response inhibition-related functional connectivity. This study demonstrates that individuals with more severe alcohol dependence exhibit less frontal connectivity with the striatum, a component of cognitive control networks important for response inhibition. These findings suggest that the fronto-striatal pathway underlying response inhibition is weakened as alcoholism progresses.

Dimensions of impulsivity among heavy drinkers, smokers, and heavy drinking smokers: singular and combined effects

Alcohol use and cigarette smoking commonly co-occur. The role impulsivity may play as a common underlying mechanism in alcohol use and cigarette smoking is of particular interest due to emerging evidence of it being a critical component across multiple forms of addiction. Impulsivity can be examined through several constructs including, risky decision-making, response inhibition, and delay reward discounting. Impulsivity and each of these specific constructs play significant roles in the initiation of drug use, continued use despite negative consequences, and potential to relapse. This study used three behavioral tasks to measure risky decision-making (balloon analog risk test; BART), response inhibition (stop signal task; SST), and delay reward discounting (delay discounting task; DDT). This study advances research on impulsivity and substance use by parsing out the various components of impulsivity and examining them across three groups, heavy drinkers only (HD) (N=107), smokers only (S) (N=67), and heavy drinking smokers (HDS) (N=213). Participants completed questionnaires, interviews, and neurocognitive tasks including the SST, BART, and DDT. Analyses supported an additive effect of alcohol and nicotine use in delay reward discounting. Heavy drinking smokers displayed steeper delay discounting of small rewards than did smokers only (p<.05) and heavy drinkers only (p<.05). This additive effect of smoking and drinking was not observed for risky decision-making and response inhibition, suggesting specificity of the effects for delay reward discounting. These findings indicate that those who both drink heavily and smoke cigarettes daily have increased delay reward discounting, than those in the S and HD groups. Future studies should examine these constructs longitudinally, as well as incorporate genetic and/or a neuroimaging component to these group comparisons in order to ascertain the biological bases of these behavioral findings.

The relationship between measures of impulsivity and alcohol misuse: an integrative structural equation modeling approach

BACKGROUND

Higher levels of impulsivity have been implicated in the development of alcohol use disorders. Recent findings suggest that impulsivity is not a unitary construct, highlighted by the diverse ways in which the various measures of impulsivity relate to alcohol use outcomes. This study simultaneously tested the following dimensions of impulsivity as determinants of alcohol use and alcohol problems: risky decision making, self-reported risk-attitudes, response inhibition, and impulsive decision making.

METHODS

Participants were a community sample of nontreatment seeking problem drinkers (n = 158). Structural equation modeling (SEM) analyses employed behavioral measures of impulsive decision making (delay discounting task [DDT]), response inhibition (stop signal task [SST]), and risky decision making (Balloon Analogue Risk Task [BART]), and a self-report measure of risk-attitudes (domain-specific risk-attitude scale [DOSPERT]), as predictors of alcohol use and of alcohol-related problems in this sample.

RESULTS

The model fits well, accounting for 38% of the variance in alcohol problems, and identified 2 impulsivity dimensions that significantly loaded onto alcohol outcomes: (i) impulsive decision making, indexed by the DDT; and (ii) risky decision making, measured by the BART.

CONCLUSIONS

The impulsive decision-making dimension of impulsivity, indexed by the DDT, was the strongest predictor of alcohol use and alcohol pathology in this sample of problem drinkers. Unexpectedly, a negative relationship was found between risky decision making and alcohol problems. The results highlight the importance of considering the distinct facets of impulsivity to elucidate their individual and combined effects on alcohol use initiation, escalation, and dependence.

Similar hyporesponsiveness of the dorsomedial prefrontal cortex in problem gamblers and heavy smokers during an inhibitory control task

BACKGROUND

Behavioral addictions like pathological gambling share many clinical characteristics with substance dependence. In addition, both types of disorders are associated with impairments in inhibitory control. Studies in patients with substance use disorders point to hyporesponsiveness of the dorsomedial prefrontal cortex. However, no such data exist on behavioral addictions.

METHODS

Using functional magnetic resonance imaging, we investigated the neural circuitry associated with impaired response inhibition in a group of male problem gamblers (n=17) using a stop signal task. We included control conditions tailored to specifically isolate neural correlates of inhibitory control. To investigate the specificity of effects, a group of heavy smokers (n=18) and a group of healthy controls (n=17) were also included.

RESULTS

Groups did not differ in behavioral performance on the stop signal task. However, both problem gamblers and heavy smokers showed hyporesponsiveness of the dorsomedial prefrontal cortex compared to healthy controls, during successful as well as failed response inhibition. These effects were robust against adjustments for depression and adult attention deficit scores.

CONCLUSIONS

These findings suggest that hypoactivation of the inhibition circuit is a shared neural mechanism in substance use disorders and behavioral addictions. As such, they support the reclassification of pathological gambling as a behavioral addiction in DSM-V.