Impulsive–compulsive disorders such as pathological gambling, hypersexuality, compulsive eating, and shopping are side effects of the dopaminergic therapy for Parkinson’s disease. With a lower prevalence, these disorders also appear in the general population. Research in the last few years has discovered that these pathological behaviors share features similar to those of substance use disorders (SUD), which has led to the term “behavioral addictions”. As in SUDs, the behaviors are marked by a compulsive drive toward and impaired control over the behavior. Furthermore, animal and medication studies, research in the Parkinson’s disease population, and neuroimaging findings indicate a common neurobiology of addictive behaviors. Changes associated with addictions are mainly seen in the dopaminergic system of a mesocorticolimbic circuit, the so-called reward system. Here we outline neurobiological findings regarding behavioral addictions with a focus on dopaminergic systems, relate them to SUD theories, and try to build a tentative concept integrating genetics, neuroimaging, and behavioral results.
Behavioral addictions; Pathological gambling; Binge eating; Compulsive buying; Hypersexuality; Substance use disorders; Mesocorticolimbic circuit; Reward system; Dopamine; Parkinson; Parkinson’s disease; Neurobiology; Risk factors; Impulse control disorders; Functional anatomy
Over the past several decades, and particularly during the last 10 to 15 years, there has been a rapid increase in the accessibility of legalized gambling in the United States and other parts of the world. Few studies have systematically explored the relationships between patterns of gambling and health status. Existing data support the notion that some gambling behaviors, particularly problem and pathological gambling, are associated with nongambling health problems. The purpose of this article is to provide a perspective on the relationship between gambling behaviors and substance use disorders, review the data regarding health associations and screening and treatment options for problem and pathological gambling, and suggest a role for generalist physicians in assessing problem and pathological gambling. A rationale for conceptualization of pathological gambling as an addictive disorder and a model proposing stress as a possible mediating factor in the relationship between gambling and health status are presented. More research is needed to investigate directly the biological and health correlates associated with specific types of gambling behaviors and to define the role for generalist physicians in the prevention and treatment of problem and pathological gambling.
addiction; pathological gambling; treatment; prevention; substance abuse
To review the neurobiological substrates of impulse control disorders (ICDs). Pathological gambling (PG) is a main focus of the review in that most biological studies of the formal ICDs have examined this disorder.
The medical database MedLine from 1966 to present was searched to identify relevant articles that were subsequently reviewed to generate this manuscript.
Preclinical studies suggest that differential brain monoamine neuromodulation is associated with impulsive decision-making and risk-taking behaviors. Clinical studies implicate multiple neurotransmitter systems (serotonergic, dopaminergic, adrenergic, and opioidergic) in the pathophysiology of PG and other ICDs. Initial neuroimaging studies have implicated the ventromedial prefrontal cortex and ventral striatum in the pathophysiology of PG and other ICDs. Genetic contributions to PG seem substantial and initial studies have implicated specific allelic polymorphisms, although genome-wide analyses have yet to be published.
Although significant advances have been made in our understanding of the neurobiology of ICDs, more research is needed to extend existing knowledge and translate these findings into clinical advances.
Pathological Gambling; Serotonin; Norepinephrine; Dopamine; Opioids; Impulsivity; Stress; Genetics; Brain Imaging; Biochemistry
Pathological gambling (PG) has recently been considered as a “behavioral” or non-substance addiction. A comparison of characteristics of PG and substance use disorders (SUDs) has clinical ramifications and could help advance future research on these conditions. Specific relationships with impulsivity and compulsivity may be central to understanding PG and SUDs.
To compare and contrast research findings in PG and SUDs pertaining to neurocogntive tasks, brain function and neurochemistry, with a focus on impulsivity and compulsivity.
Multiple similarities were found between PG and SUDs, including poor performance on neurocognitive tasks, specifically with respect to impulsive choice and response tendencies and compulsive features (e.g., response perseveration and action with diminished relationship to goals or reward). Findings suggest dysfunction involving similar brain regions, including the ventromedial prefrontal cortex (PFC) and striatum and similar neurotransmitter systems, including dopaminergic and serotonergic. Unique features exist which may in part reflect influences of acute or chronic exposures to specific substances.
Both similarities and differences exist between PG and SUDs. Understanding these similarities more precisely may facilitate treatment development across addictions, whereas understanding differences may provide insight into treatment development for specific disorders. Individual differences in features of impulsivity and compulsivity may represent important endophenotypic targets for prevention and treatment strategies.
Iowa Gambling Task; delay discounting; neuroimaging; alcohol; cocaine; dopamine; serotonin; glutamate; frontal cortex; striatum
Pathological gambling and substance use disorders are highly comorbid, possibly because they both stem from a similar process—impulsivity. Although much data exist regarding the association between delay discounting and these psychiatric disorders, relatively little research has examined probability discounting and its relationship with either substance use or gambling.
The goal of the current study was to compare rates of probability and delay discounting in a large population of pathological gamblers with and without a history of substance use problems.
Treatment-seeking pathological gamblers with (n=117) and without (n=119) a history of substance use problems completed questionnaires about discounting of hypothetical monetary outcomes and the Eysenck Impulsivity Questionnaire. The delay discounting questionnaire involved choices between a smaller amount of money delivered immediately versus a larger amount delivered later, and the probability questionnaire was comprised of choices between a smaller certain versus a larger probabilistic monetary outcome. Hyperbolic functions estimated delay and probability discounting rates based on the indifference points obtained through the questionnaires.
Results revealed significant effects of substance use problem status on delay but not on probability discounting, with no significant correlation noted between the two discounting processes. Only delay discounting correlated with Eysenck impulsivity scores.
These data suggest that delay and probability discounting tap different dimensions, and delay discounting is more closely linked with substance use problem histories in pathological gamblers.
pathological gamblers; substance use problems; choice; delay discounting; probability discounting; impulsivity
Gambling disorder sufferers prefer immediately larger rewards despite long term losses on the Iowa Gambling Task (IGT), and these impairments are associated with dopamine dysfunctions. Dopamine is a neurotransmitter linked with temporal and structural dysfunctions in substance use disorder, which has supported the idea of impaired decision-making and dopamine dysfunctions in gambling disorder. However, evidence from substance use disorders cannot be directly transferred to gambling disorder. This article focuses on three hypotheses of dopamine dysfunctions in gambling disorder, which appear to be “fallacies,” i.e., have not been supported in a series of positron emission tomography (PET) studies. The first “fallacy” suggests that gambling disorder sufferers have lower dopamine receptor availability, as seen in substance use disorders. However, no evidence supported this hypothesis. The second “fallacy” suggests that maladaptive decision-making in gambling disorder is associated with higher dopamine release during gambling. No evidence supported the hypothesis, and the literature on substance use disorders offers limited support for this hypothesis. The third “fallacy” suggests that maladaptive decision-making in gambling disorder is associated with higher dopamine release during winning. The evidence did not support this hypothesis either. Instead, dopaminergic coding of reward prediction and uncertainty might better account for dopamine dysfunctions in gambling disorder. Studies of reward prediction and reward uncertainty show a sustained dopamine response toward stimuli with maximum uncertainty, which may explain the continued dopamine release and gambling despite losses in gambling disorder. The findings from the studies presented here are consistent with the notion of dopaminergic dysfunctions of reward prediction and reward uncertainty signals in gambling disorder.
gambling disorder; Iowa Gambling Task (IGT); dopamine; addiction; positron-emission tomography
Gambling is a prevalent recreational behaviour. Approximately 5% of adults have been estimated to experience problems with gambling. The most severe form of gambling, pathological gambling (PG), is recognized as a mental health condition. Two alternate non-mutually exclusive conceptualizations of PG have considered it as an obsessive-compulsive spectrum disorder and a ‘behavioural’ addiction. The most appropriate conceptualization of PG has important theoretical and practical implications. Data suggest a closer relationship between PG and substance use disorders than exists between PG and obsessive-compulsive disorder. This paper will review data on the neurobiology of PG, consider its conceptualization as a behavioural addiction, discuss impulsivity as an underlying construct, and present new brain imaging findings investigating the neural correlates of craving states in PG as compared to those in cocaine dependence. Implications for prevention and treatment strategies will be discussed.
gambling; addiction; impulsivity; impulse control disorder; brain imaging; functional magnetic resonance imaging
The Iowa Gambling Task (IGT) is widely used in investigations of decision making. A growing number of studies have linked performance on this task to personality differences, with the aim of explaining the large degree of variability in healthy individuals' performance of the task. However, this line of research has yielded inconsistent results. In the present study, we tested whether increasing the conflict between short-term and long-term gains in the IGT can clarify personality-related modulations of decision making. We assessed performance on the original IGT as a function of the personality traits typically involved in risky decision making (i.e., impulsivity, sensation seeking, sensitivity to reward and punishment). The impact of these same personality traits was also evaluated on a modified version of the task in which the difference in immediate reward magnitude between disadvantageous and advantageous decks was increased, while keeping the net gain fixed. The results showed that only in this latter IGT variant were highly impulsive individuals and high sensation seekers lured into making disadvantageous choices. The opposite seems to be the case for participants who were highly sensitive to punishment, although further data are needed to corroborate this finding. The present preliminary results suggest that the IGT variant used in this study could be more effective than the original task at identifying personality effects in decision making. Implications for dispositional and situational effects on decision making are discussed.
Pramipexole (PPX) is a dopamine agonist medication that has been implicated in the development of pathological gambling and other impulse control disorders. Johnson, Madden, Brewer, Pinkston, and Fowler (2011) reported that PPX increased male rats’ preference for gambling-like rewards (those arranged according to a variable-ratio schedule) over predictable rewards (those obtained from a fixed-ratio schedule). The present experiment explored the possibility that Johnson et al. underestimated the effects of PPX on gambling-like choices by constraining their rats’ daily income. In the present experiment conducted in a closed economy, PPX produced a dose-related increase in choice of the gambling-like alternative. In a control condition, PPX did not disrupt choice, suggesting the increased preference for gambling-like rewards was not due to nonspecific drug effects. Our findings are qualitatively consistent with those of Johnson et al., although the dose-related effect and larger effect size in the current study suggest that the effect of PPX on gambling-like choices is more pronounced when income was not constrained. This finding is consistent with clinical reports suggesting PPX is related to the development of problem gambling in humans.
pramipexole; dopamine agonist; gambling; Parkinson’s disease; rat
As a behavioral addiction with clinical and phenomenological similarities to substance addiction, recreational and pathological gambling represent models for studying the neurobiology of addiction, without the confounding deleterious brain effects which may occur from chronic substance abuse.
A community sample of individuals aged 18–65 years who gamble was solicited through newspaper advertising. Subjects were grouped a priori into three groups (no-risk, at-risk, and pathological gamblers) based on a diagnostic interview. All subjects underwent a psychiatric clinical interview and neurocognitive tests assessing motor impulsivity and cognitive flexibility. Subjects with a current axis I disorder, history of brain injury/trauma, or implementation or dose changes of psychoactive medication within 6 weeks of study enrollment were excluded.
A total of 135 no-risk, 69 at-risk and 46 pathological gambling subjects were assessed. Pathological gamblers were significantly older, and exhibited significant deficiencies in motor impulse control (stop-signal reaction times), response speed (median ‘go’ trial response latency) and cognitive flexibility [total intra-dimensional/extra-dimensional (IDED) errors] versus controls. The finding of impaired impulse control and cognitive flexibility was robust in an age-matched subgroup analysis of pathological gamblers. The no-risk and at-risk gambling groups did not significantly differ from each other on task performance.
Impaired response inhibition and cognitive flexibility exist in people with pathological gambling compared with no-risk and at-risk gamblers. The early identification of such illness in adolescence or young adulthood may aid in the prevention of addiction onset of such disabling disorders.
Cognition; gambling; impulsivity
Despite reasonable knowledge of pathological gambling (PG), little is known of its cognitive antecedents. We evaluated decision-making and impulsivity characteristics in people at risk of developing PG using neuropsychological tests. Non-treatment seeking volunteers (18-29 years) who gamble ≥5 times/year were recruited from the general community, and split into two groups: those “at risk” of developing PG (n=74) and those social, non-problem gamblers (n=112). Participants undertook the Cambridge Gamble and Stop-signal tasks and were assessed with the Mini-International Neuropsychiatric Interview and the Yale Brown Obsessive Compulsive Scale Modified for Pathological Gambling. On the Cambridge Gamble task, the at- risk subjects gambled more points overall, were more likely to go bankrupt, and made more irrational decisions under situations of relative risk ambiguity. On the Stop-signal task, at- risk gamblers did not differ from the social, non-problem gamblers in terms of motor impulse control (stop-signal reaction times). Findings suggest that selective cognitive dysfunction may already be present in terms of decision-making in at-risk gamblers, even before psychopathology arises. These findings implicate selective decision-making deficits and dysfunction of orbitofronto-limbic circuitry in the chain of pathogenesis between social, non-problematic and pathological gambling.
Pathological Gambling; Pathogenesis; Addiction; Cognitive Dysfunction; Cognition; Inhibition
Gambling, including pathological gambling and problem gambling, has received increased attention from clinicians and researchers over the past three decades since gambling opportunities have expanded around the world. Gambling disorders affect 0.2–5.3% of adults worldwide, although measurement and prevalence varies according to the screening instruments and methods used, and availability and accessibility of gambling opportunities. Several distinct treatment approaches have been favorably evaluated, such as cognitive behavioral and brief treatment models and pharmacological interventions. Although promising, family therapy and support from Gamblers Anonymous are less well empirically supported. Gambling disorders are highly comorbid with other mental health and substance use disorders, and a further understanding is needed of both the causes and treatment implications of this disorder. This article reviews definition, causes and associated features with substance abuse, screening and diagnosis, and treatment approaches.
Addiction; gambling; substance use
Mesocorticolimbic neurocircuitry and impulsivity have both been implicated in pathological gambling (PG) and in reward processing. However, the neural underpinnings of specific phases of reward and loss processing in PG and their relationships to impulsivity remain only partially understood. The present functional magnetic resonance imaging study examined brain activity associated with different phases of reward and loss processing in PG. Given an inverse relationship between ventral striatal recruitment during anticipation of monetary rewards and impulsivity in alcohol dependence, the current study explored whether a similar association might also be present in PG.
Fourteen adults with PG and 14 control comparison (CC) participants performed the Monetary Incentive Delay Task (MIDT) to identify brain activation changes associated with reward/loss prospect, reward/loss anticipation and reward/loss notification. Impulsivity was assessed separately using the Barratt Impulsiveness Scale.
Relative to the CC group, the PG group exhibited significantly reduced activity in the ventromedial prefrontal cortex, insula and ventral striatum during several phases, including the prospect and anticipation phases of both gain and losses. Activity in the ventral striatum correlated inversely with levels of impulsivity in PG participants, consistent with prior findings in alcohol dependence.
Relatively decreased activity in cortico-striatal neurocircuitry during multiple phases of reward processing suggests consistent alterations in neurocircuitry underlying incentive valuation and loss prediction. Together with findings in alcohol dependence, these results suggest that impulsive tendencies in addictions may be reflected in diminished ventral striatal activations to reward anticipation and may represent targets for treatment development in addictions.
fMRI; vmPFC; ventral striatum; insula; incentive; gambling
Impulsivity is a hallmark of problem gambling. However, impulsivity is not a unitary construct and this study investigated the relationship between problem gambling severity and two facets of impulsivity: impulsive action (impaired ability to withhold a motor response) and impulsive choice (abnormal aversion for the delay of reward).
The recruitment includes 65 problem gamblers and 35 normal control participants. On the basis of DSM-IV-TR criteria, two groups of gamblers were distinguished: problem gamblers (n = 38) and pathological gamblers (n = 27) with similar durations of gambling practice. Impulsive action was assessed using a response inhibition task (the stop-signal task). Impulsive choice was estimated with the delay-discounting task. Possible confounds (e.g., IQ, mood, ADHD symptoms) were recorded.
Both problem and pathological gamblers discounted reward at a higher rate than their controls, but only pathological gamblers showed abnormally low performance on the most demanding condition of the stop-signal task. None of the potential confounds covaried with these results.
These results suggest that, whereas abnormal impulsive choice characterizes all problem gamblers, pathological gamblers' impairments in impulsive action may represent an important developmental pathway of pathological gambling.
Impairments in self-regulatory behaviour reflect a deficit in executive functioning and decision-making, as well as higher levels of self-reported impulsivity, and may be involved in the development and maintenance of addictive disorders. We sought to explore the association between self-reported impulsivity and neurocognitive measures, and their association with treatment outcome in pathologic gambling.
We assessed patients with pathologic gambling using executive functioning and decision-making tests and self-report measures of impulsivity. Patients underwent cognitive–behavioural therapy (CBT) for pathologic gambling.
We included 88 patients (8% women) in our study. High self-reported extravagance was associated with poor performance in the Iowa Gambling Task (IGT)-ABCD version. High impulsiveness, low disorderliness, high exploratory excitability (trend), poor backward block span and poor IGT-EFGH scores (trend) predicted dropout. We observed no self-reported or neurocognitive predictors of relapse or number of treatment sessions attended.
Most participants were slot-machine gamblers seeking treatment. No follow-up data and no control group were included in the study. The missing sample (i.e., individuals who were recruited and assessed in the pretreatment stage but who chose not to begin treatment) had higher extravagance scores than the final sample.
Neurocognitive reward sensitivity was related to self-reported overspending behaviour. Self-regulatory impairments (especially rash impulsiveness and punishment sensitivity) and executive dysfunction predicted only dropout of CBT in participants with pathologic gambling. Different neurocognitive processes and personality traits might mediate treatment response to psychological therapy of pathologic gambling according to the specific target variable assessed.
Failures in cortical control of fronto-striatal neural circuits may underpin impulsive and compulsive acts. In this narrative review, we explore these behaviors from the perspective of neural processes and consider how these behaviors and neural processes contribute to mental disorders such as obsessive–compulsive disorder (OCD), obsessive–compulsive personality disorder, and impulse-control disorders such as trichotillomania and pathological gambling. We present findings from a broad range of data, comprising translational and human endophenotypes research and clinical treatment trials, focussing on the parallel, functionally segregated, cortico-striatal neural projections, from orbitofrontal cortex (OFC) to medial striatum (caudate nucleus), proposed to drive compulsive activity, and from the anterior cingulate/ventromedial prefrontal cortex to the ventral striatum (nucleus accumbens shell), proposed to drive impulsive activity, and the interaction between them. We suggest that impulsivity and compulsivity each seem to be multidimensional. Impulsive or compulsive behaviors are mediated by overlapping as well as distinct neural substrates. Trichotillomania may stand apart as a disorder of motor-impulse control, whereas pathological gambling involves abnormal ventral reward circuitry that identifies it more closely with substance addiction. OCD shows motor impulsivity and compulsivity, probably mediated through disruption of OFC-caudate circuitry, as well as other frontal, cingulate, and parietal connections. Serotonin and dopamine interact across these circuits to modulate aspects of both impulsive and compulsive responding and as yet unidentified brain-based systems may also have important functions. Targeted application of neurocognitive tasks, receptor-specific neurochemical probes, and brain systems neuroimaging techniques have potential for future research in this field.
impulsive; compulsive; endophenotypes; serotonin; dopamine; Cognition; Psychiatry & Behavioral Sciences; Animal models; Biological Psychiatry; OCD; impulsivity; compulsivity; translational
Individuals with addictive disorders, including substance abusers and pathological gamblers, discount or devalue rewards delayed in time more than controls. Theoretically, preference for probabilistic rewards is directly related to gambling, but limited empirical research has examined probabilistic discounting in individuals with pathological gambling. This study evaluated probability and delay discounting in treatment-seeking pathological gamblers and their association with gambling treatment outcomes during and following treatment. At time of treatment entry, 226 pathological gamblers completed probability and delay discounting tasks. They were then randomized to one of three treatment conditions, and gambling behavior was measured throughout treatment and at a one-year follow-up assessment. After controlling for possibly confounding variables and treatment condition, more shallow probability discounting was associated with greater reductions in amounts wagered during treatment and likelihood of gambling abstinence at the end of treatment and throughout the follow-up period. No associations were noted between delay discounting and gambling treatment outcomes. These data suggest that probability discounting may be an important construct in understanding pathological gambling and its treatment.
probability discounting; pathological gambling; treatment
Two studies were conducted to test and explain the relation of mindfulness to the severity of gambling outcomes among frequent gamblers. In both studies, dispositional mindfulness related to less severe gambling outcomes as measured by a DSM-IV-based screen for pathological gambling, even after controlling for gambling frequency and dispositional self-control. Study 2 extended this finding in showing that the association between mindfulness and lower pathological gambling was partially mediated by better performance on two risk-taking tasks that capture overconfidence, risky bet acceptance, and myopic focus on reward. These studies suggest a role for mindfulness in lessening the severity of gambling problems and making adaptive decisions, especially in risk-relevant contexts.
MINDFULNESS; OVERCONFIDENCE; RISK-TAKING; GAMBLING; DECISION-MAKING
Research has found that children who have parents with an addiction may be more vulnerable to developing psychopathology compared to children without parental addiction. We compared young adult, recreational gamblers with and without parental addiction on measures of gambling behavior and impulsivity. A total of 286 recreational gamblers (defined as having gambled at least five times in the past 12 months) between the ages of 18 and 29 participated in an initial intake of a longitudinal study assessing susceptibility to pathological gambling. Trained staff interviewed subjects and subjects completed cognitive testing and self-report measures. Fifty-three subjects (18.53%) reported at least one parent with an addiction (including alcohol and substance dependence and pathological gambling). Subjects with at least one addicted parent were significantly more likely to report problems resulting from gambling, have significantly greater rates of psychiatric comorbidity, and report significantly more current marijuana and tobacco use. Subjects with an addicted parent were not significantly different on measures of impulsivity. These findings suggest that even at a stage of low-risk gambling, before what has been considered a psychopathology arises, those with a possible environmental and/or genetic risk of addiction exhibit a range of problematic behaviors.
Pathological Gambling; Psychopathology; Addiction; Family History; Young Adults
To examine whether gambling cue reactivity is cue-specific, 47 scratch-off lottery players and 47 horse race gamblers were presented with video clips of their preferred and non-preferred modes of gambling, and two control stimuli including an exciting car race and a mental stressor task while heart rates, excitement, and urge to gamble were being measured. Heart rates for both groups of gamblers were highest to the mental stressor and did not differ in response to the other three cues. Excitement for both groups was highest in response to the action cues (horse race and car chase). Urge to gamble was significantly higher for each group to their preferred mode of gambling. A post-hoc exploratory analysis comparing social gamblers (n=54) and probable pathological gamblers (n=40) revealed a similar pattern of responses. However, pathological gamblers reported overall significantly higher urges to gamble than social gamblers. As urges have been shown to play a pivotal role in addictive behaviors and relapse, the current findings may have implications for the development of gambling problems and relapse after successful treatment.
cue-reactivity; gambling; heart rate; excitement; urge
Surface-level differences in the reward and punishment variants, specifically greater long-term decision making in the punishment variant of the Iowa Gambling Task (IGT) observed in previous studies led to the present comparison of long-term decision making in the two IGT variants (n = 320, male = 160). It was contended that risk aversion triggered by a positive frame of the reward variant and risk seeking triggered by a negative frame of the punishment variant appears as long-term decision making in the two IGT variants. Apart from the frame of the variant as a within-subjects factor (variant type: reward and punishment), the order in which the frame was triggered (order type: reward–punishment or punishment–reward), and the four types of instructions that delineated motivation toward reward from that of punishment (reward, punishment, reward and punishment, and no-hint) were hypothesized to have an effect on foresighted decision making in the IGT. As expected, long-term decision making differed across the two IGT variants suggesting that the frame of the variant has an effect on long-term decision making in the IGT (p < 0.001). The order in which a variant was presented, and the type of the instructions that were used both had an effect on long-term decision making in the two IGT variants (p < 0.05). A post hoc test suggested that the instructions that differentiated between reward and punishment resulted in greater foresight than the commonly used IGT instructions that fail to distinguish between reward and punishment. As observed in previous studies, there were more number of participants (60%) who showed greater foresight in the punishment variant than in the reward variant (p < 0.001). The results suggest that foresight in IGT decision making is sensitive to reward and punishment frame in an asymmetric manner, an observation that is aligned with the behavioral decision making framework. Benefits of integrating findings from behavioral studies in decision neuroscience are discussed, and a need to investigate cultural differences in the IGT studies is pointed out.
Iowa gambling task; reward–punishment; instructions; decision making; framing effect
Abnormal cue reactivity is a central characteristic of addiction, associated with increased activity in motivation, attention and memory related brain circuits. In this neuroimaging study, cue reactivity in problem gamblers (PRG) was compared with cue reactivity in heavy smokers (HSM) and healthy controls (HC). A functional magnetic resonance imaging event-related cue reactivity paradigm, consisting of gambling, smoking-related and neutral pictures, was employed in 17 treatment-seeking non-smoking PRG, 18 non-gambling HSM, and 17 non-gambling and non-smoking HC. Watching gambling pictures (relative to neutral pictures) was associated with higher brain activation in occipitotemporal areas, posterior cingulate cortex, parahippocampal gyrus and amygdala in PRG compared with HC and HSM. Subjective craving in PRG correlated positively with brain activation in left ventrolateral prefrontal cortex and left insula. When comparing the HSM group with the two other groups, no significant differences in brain activity induced by smoking cues were found. In a stratified analysis, the HSM subgroup with higher Fagerström Test for Nicotine Dependence scores (FTND M = 5.4) showed higher brain activation in ventromedial prefrontal cortex, rostral anterior cingulate cortex, insula and middle/superior temporal gyrus while watching smoking-related pictures (relative to neutral pictures) than the HSM subgroup with lower FTND scores (FTND M = 2.9) and than non-smoking HC. Nicotine craving correlated with activation in left prefrontal and left amygdala when viewing smoking-related pictures in HSM. Increased regional responsiveness to gambling pictures in brain regions linked to motivation and visual processing is present in PRG, similar to neural mechanisms underlying cue reactivity in substance dependence. Increased brain activation in related fronto-limbic brain areas was present in HSM with higher FTND scores compared with HSM with lower FTND scores.
Addiction; cue reactivity; fMRI; impulse control disorder; nicotine dependence; pathological gambling
Delay discounting describes the decline in the value of a reinforcer as the delay to that reinforcer increases. A review of the available studies revealed that steep delay discounting is positively correlated with problem or pathological gambling. One hypothesis regarding this correlation derives from the discounting equation proposed by Mazur (1989). According to the equation, steeper discounting renders the difference between fixed-delayed rewards and gambling-like variable-delayed rewards larger; with the latter being more valuable. The present study was designed to test this prediction by first assessing rats’ impulsive choices across four delays to a larger-later reinforcer. A second condition quantified strength of preference for mixed- over fixed-delays, with the duration of the latter adjusted between sessions to achieve indifference. Strength of preference for the mixed-delay alternative is given by the fixed delay at indifference (lower fixed-delay values reflect stronger preferences). Percent impulsive choice was not correlated with the value of the fixed delay at indifference and, therefore, the prediction of the hyperbolic model of gambling was not supported. A follow-up assessment revealed a significant decrease in impulsive choice after the second condition. This shift in impulsive choice could underlie the failure to observe the predicted correlation between impulsive choice and degree of preference for mixed- over fixed delays.
Delay discounting; impulsivity; delay; gambling; rat
Less supervision by the executive system after disruption of the right prefrontal cortex
leads to increased risk taking in gambling because superficially attractive—but
risky—choices are not suppressed. Similarly, people might gamble more in multitask
situations than in single-task situations because concurrent executive processes usually
interfere with each other. In the study reported here, we used a novel monetary
decision-making paradigm to investigate whether multitasking could reduce rather than
increase risk taking in gambling. We found that performing a task that induced cautious
motor responding reduced gambling in a multitask situation (Experiment 1). We then found
that a short period of inhibitory training lessened risk taking in gambling at least 2 hr
later (Experiments 2 and 3). Our findings indicate that proactive motor control strongly
affects monetary risk taking in gambling. The link between control systems at different
cognitive levels might be exploited to develop new methods for rehabilitation of addiction
and impulse-control disorders.
gambling; impulse control; executive functions; stop signal; training; response inhibition; self-control
Our ability to measure the cognitive components of complex decision-making across species has greatly facilitated our understanding of its neurobiological mechanisms. One task in particular, reversal learning, has proven valuable in assessing the inhibitory processes that are central to executive control. Reversal learning measures the ability to actively suppress reward-related responding and to disengage from ongoing behavior, phenomena that are biologically and descriptively related to impulsivity and compulsivity. Consequently, reversal learning could index vulnerability for disorders characterized by impulsivity, such as proclivity for initial substance abuse, as well as the compulsive aspects of dependence.
Though we describe common variants and similar tasks, we pay particular attention to discrimination reversal learning, its supporting neural circuitry, neuropharmacology and genetic determinants. We also review the utility of this task in measuring impulsivity and compulsivity in addictions.
We restrict our review to instrumental, reward-related reversal learning studies, as they are most germane to addiction.
The research reviewed here suggests that discrimination reversal learning may be used as a diagnostic tool for investigating the neural mechanisms that mediate impulsive and compulsive aspects of pathological reward-seeking and –taking behaviors. Two interrelated mechanisms are posited for the neuroadaptations in addiction that often translate to poor reversal learning: frontocorticostriatal circuitry dysregulation and poor dopamine (D2 receptor) modulation of this circuitry. These data suggest new approaches to targeting inhibitory control mechanisms in addictions.
orbitofrontal cortex; striatum; decision-making; dopamine; serotonin; psychostimulant; methamphetamine; noradrenaline; response control