Iris M. Balodis

Diminished frontostriatal activity during processing of monetary rewards and losses in pathological gambling.

BACKGROUND 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. METHODS Fourteen adults with PG and 14 control comparison participants performed the Monetary Incentive Delay Task 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. RESULTS Relative to the control comparison 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 gains and losses. Activity in the ventral striatum correlated inversely with levels of impulsivity in PG participants, consistent with prior findings in alcohol dependence. CONCLUSIONS Relatively decreased activity in corticostriatal 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.

Monetary Reward Processing in Obese Individuals With and Without Binge Eating Disorder

BACKGROUND An important step in obesity research involves identifying neurobiological underpinnings of nonfood reward processing unique to specific subgroups of obese individuals. METHODS Nineteen obese individuals seeking treatment for binge eating disorder (BED) were compared with 19 non-BED obese individuals (OB) and 19 lean control subjects (LC) while performing a monetary reward/loss task that parses anticipatory and outcome components during functional magnetic resonance imaging. Differences in regional activation were investigated in BED, OB, and LC groups during reward/loss prospect, anticipation, and notification. RESULTS Relative to the LC group, the OB group demonstrated increased ventral striatal and ventromedial prefrontal cortex activity during anticipatory phases. In contrast, the BED group relative to the OB group demonstrated diminished bilateral ventral striatal activity during anticipatory reward/loss processing. No differences were observed between the BED and LC groups in the ventral striatum. CONCLUSIONS Heterogeneity exists among obese individuals with respect to the neural correlates of reward/loss processing. Neural differences in separable groups with obesity suggest that multiple, varying interventions might be important in optimizing prevention and treatment strategies for obesity.

Divergent neural substrates of inhibitory control in binge eating disorder relative to other manifestations of obesity

An important endeavor involves increasing our understanding of biobehavioral processes underlying different types of obesity. The current study investigated the neural correlates of cognitive control (involving conflict monitoring and response inhibition) in obese individuals with binge eating disorder (BED) as compared to BMI‐matched non‐BED obese (OB) individuals and lean comparison (LC) participants. Alterations in cognitive control may contribute to differences in behavioral control over eating behaviors in BED and obesity.

Anticipatory reward processing in addicted populations: a focus on the monetary incentive delay task.

Advances in brain imaging techniques have allowed neurobiological research to temporally analyze signals coding for the anticipation of reward. In addicted populations, both hyporesponsiveness and hyperresponsiveness of brain regions (e.g., ventral striatum) implicated in drug effects and reward system processing have been reported during anticipation of generalized reward. We discuss the current state of knowledge of reward processing in addictive disorders from a widely used and validated task: the monetary incentive delay task. Only studies applying the monetary incentive delay task in addicted and at-risk adult populations are reviewed, with a focus on anticipatory processing and striatal regions activated during task performance as well as the relationship of these regions with individual difference (e.g., impulsivity) and treatment outcome variables. We further review drug influences in challenge studies as a means to examine acute influences on reward processing in abstinent, recreationally using, and addicted populations. Generalized reward processing in addicted and at-risk populations is often characterized by divergent anticipatory signaling in the ventral striatum. Although methodologic and task variations may underlie some discrepant findings, anticipatory signaling in the ventral striatum may also be influenced by smoking status, drug metabolites, and treatment status in addicted populations. Divergent results across abstinent, recreationally using, and addicted populations demonstrate complexities in interpreting findings. Future studies would benefit from focusing on characterizing how impulsivity and other addiction-related features relate to anticipatory striatal signaling over time. Additionally, identifying how anticipatory signals recover or adjust after protracted abstinence will be important in understanding recovery processes.

Binge drinking in undergraduates: relationships with sex, drinking behaviors, impulsivity, and the perceived effects of alcohol

Binge drinking on university campuses is associated with social and health-related problems. To determine the factors that may predict this behavior, we collected information on alcohol use, alcohol expectations, and impulsivity from 428 undergraduate students attending a Canadian university. The subjective effects of a binge drinking dose of alcohol were assessed in a subset of participants. In the larger sample, 72% of students reported drinking at or above binge drinking thresholds on a regular basis. Men reported alcohol consumption per drinking occasion, which was consistent with other studies, but the frequency of drinking occasions among women was higher than in earlier studies, suggesting that consumption in women may be increasing. Compared with men, women reported different expectations of alcohol, specifically related to sociability and sexuality. Self-reported impulsivity scores were related, albeit weakly, to drinking behaviors and to expectations in both the sexes. Finally, intoxicated binge drinkers reported feeling less intoxicated, liking the effects more, and wanting more alcohol than did non-binge drinkers receiving an equivalent dose of alcohol. These results have implications for sex-specific prevention strategies for binge drinking on university campuses.

The other side of the curve: Examining the relationship between pre-stressor physiological responses and stress reactivity

There is widespread consensus that stress induces dramatic physiological changes, but no agreement on the quantitative parameters that are appropriate to measure these responses. More importantly, the interpretation of various stress measurements, and how individual responses should be evaluated, has not been properly addressed. Even the definition of baseline, against which stress responses must be measured, is not clearly established. The current experiment sought to address these shortcomings by comparing the predictive value of different calculated parameters for psychosocial and physiological measures of stress across individuals. Subjects were 29 male and 59 female healthy undergraduate students with saliva samples collected over a 3-h interval that included a Trier Social Stress Test. Salivary cortisol and alpha-amylase response were analyzed using the absolute concentration, the percent change in concentration, the area under the curve (Pruessner et al., 2003), and the arrival index (change from arrival to 1h after arrival). The arrival index correlated with the subsequent stress response for both cortisol (r=0.76, p<0.01) and alpha-amylase (r=0.86, p<0.01). The arrival index for both cortisol and alpha-amylase was also related to subjective ratings of anxiety following the psychosocial stressor. A subset of individuals with high self-reported anxiety also displayed higher reactivity in response to the psychosocial stressor. Thus, the magnitude of the difference in cortisol and alpha-amylase between arrival and 1h after arrival was a predictor of subsequent stress reactivity. These findings suggest that different psychosocial profiles may be reflected in cortisol and alpha-amylase changes. For this reason: (1) a recovery period after arrival is essential to establish a baseline, (2) the difference between arrival and post-recovery period baseline should be included in experimental designs as a predictive variable, and (3) transformation of individual measures into proportional changes relative to the arrival sample is very likely to obscure important underlying individual differences.

A pilot study linking reduced fronto-striatal recruitment during reward processing to persistent bingeing following treatment for binge-eating disorder

OBJECTIVE The primary purpose of this study was to examine neurobiological underpinnings of reward processing that may relate to treatment outcome for binge-eating disorder (BED). METHOD Prior to starting treatment, 19 obese persons seeking treatment for BED performed a monetary incentive delay task during functional magnetic resonance imaging (fMRI). Analyses examined how the neural correlates of reward processing related to binge-eating status after 4-months of treatment. RESULTS Ten individuals continued to report binge-eating (BEpost-tx ) following treatment and 9 individuals did not (NBEpost-tx ). The groups did not differ in body mass index. The BEpost-tx group relative to the NBEpost-tx group showed diminished recruitment of the ventral striatum and the inferior frontal gyrus during the anticipatory phase of reward processing and reduced activity in the medial prefrontal cortex during the outcome phase of reward processing. DISCUSSION These results link brain reward circuitry to treatment outcome in BED and suggest that specific brain regions underlying reward processing may represent important therapeutic targets in BED.

A preliminary investigation of Stroop-related intrinsic connectivity in cocaine dependence: associations with treatment outcomes.

Abstract Background: Cocaine-dependent individuals demonstrate neural and behavioral differences compared to healthy comparison subjects when performing the Stroop color-word interference test. Stroop measures also relate to treatment outcome for cocaine dependence. Intrinsic connectivity analyses assess the extent to which task-related regional brain activations are related to each other in the absence of defining a priori regions of interest. Objective: This study examined 1) the extent to which cocaine-dependent and non-addicted individuals differed on measures of intrinsic connectivity during fMRI Stroop performance; and 2) the relationships between fMRI Stroop intrinsic connectivity and treatment outcome in cocaine dependence. Methods: Sixteen treatment-seeking cocaine-dependent patients and matched non-addicted comparison subjects completed an fMRI Stroop task. Between-group differences in intrinsic connectivity were assessed and related to self-reported and urine-toxicology-based cocaine-abstinence measures. Results: Cocaine-dependent patients vs. comparison subjects showed less intrinsic connectivity in cortical and subcortical regions. When adjusting for individual degree of intrinsic connectivity, cocaine-dependent vs. comparison subjects showed relatively greater intrinsic connectivity in the ventral striatum, putamen, inferior frontal gyrus, anterior insula, thalamus and substantia nigra. Non-mean-adjusted intrinsic-connectivity measures in the midbrain, thalamus, ventral striatum, substantia nigra, insula and hippocampus negatively correlated with measures of cocaine abstinence. Conclusion: The diminished intrinsic connectivity in cocaine-dependent vs. comparison subjects suggests poorer communication across brain regions during cognitive-control processes. In mean-adjusted analyses, the cocaine-dependent group displayed relatively greater Stroop-related connectivity in regions implicated in motivational processes in addictions. The relationships between treatment outcomes and connectivity in the midbrain and basal ganglia suggest that connectivity represents a potential treatment target.

Neurobiological considerations in understanding behavioral treatments for pathological gambling.

Pathological gambling (PG), a disorder currently categorized as an impulse-control disorder but being considered as a nonsubstance addiction in Diagnostic and Statistical Manual of Mental Disorders (5th ed.) discussions, represents a significant public health concern. Over the past decade, considerable advances have been made with respect to understanding the biological underpinnings of PG. Research has also demonstrated the efficacies of multiple treatments, particularly behavioral therapies, for treating PG. Despite these advances, relatively little is known regarding how biological measures, particularly those assessing brain function, relate to treatments for PG. In this article, we present a conceptual review focusing on the neurobiology of behavioral therapies for PG. To illustrate issues related to study design, we present proof-of-concept preliminary data that link Stroop-related brain activations prior to treatment onset to treatment outcome in individuals with PG receiving a cognitive-behavioral treatment incorporating aspects of imaginal desensitization and motivational interviewing. We conclude with recommendations about current and future directions regarding how to incorporate and translate biological findings into improved therapies for individuals with nonsubstance and substance addictions.

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.