Anouk Scheres

Ventral-striatal responsiveness during reward anticipation in ADHD and its relation to trait impulsivity in the healthy population: a meta-analytic review of the fMRI literature.

A review of the existing functional magnetic resonance imaging (fMRI) studies on reward anticipation in patients with attention-deficit/hyperactivity disorder (ADHD) is provided. Meta-analysis showed a significant medium effect size (Cohens d=0.48-0.58) in terms of ventral-striatal (VS)-hyporesponsiveness in ADHD. Studies on VS-responsiveness and trait impulsivity in the healthy population demonstrate the opposite relationship, i.e. impulsivity-scores positively correlated with VS activation during reward processing. Against the background that ADHD may represent an extreme on a continuum of normal variability, the question arises as to how these contrasting findings can be integrated. We discuss three theoretical approaches, each of which integrates the opposing findings: (1) an inverted-u-shape model; (2) a (genetic) moderator model; and (3) the unrelated model. We conclude that at the present stage the number of existing studies in the healthy population as well as in ADHD groups is too small for a final answer. Therefore, our presented integrative approaches should be understood as an attempt to frame future research directions by generating testable hypotheses and giving practical suggestions for future studies.

Distinct age-related differences in temporal discounting and risk taking in adolescents and young adults

Age-related differences in temporal discounting (TD) and risk taking, and their association, were examined in adolescents and young adults (n = 337) aged 12-27 years. Since monetary rewards are typically used in TD and risk-taking tasks, the association between monetary reward valuation and age and decision making in these tasks was explored as well. TD declined linearly with age, with a particularly sharp decline from 15 to 16 years. In contrast, risk taking was not correlated with age and TD. Reward valuation was not associated with TD and risk taking, and age-related differences in TD remained significant after controlling for reward valuation. Together, these findings suggest that risk taking and TD are two separate constructs with distinct age-related differences in adolescence and young adulthood.

The neural correlates of temporal reward discounting.

Temporal reward discounting (TD) refers to the decrease in subjective value of a reward when the delay to that reward increases. In recent years, a growing number of studies on the neural correlates of temporal reward discounting have been conducted. This article focuses on functional magnetic resonance imaging (fMRI) studies on TD in humans. First, we describe the different types of tasks (also from behavioral studies) and the dependent variables. Subsequently, we discuss the evidence for three neurobiological models of TD: the dual-systems model, the single-system model and the self-control model. Further, studies in which nontraditional tasks (e.g., with nonmonetary rewards) were used to study TD are reviewed. Finally, we discuss the neural correlates of individual differences in discounting, and its development across the lifespan. We conclude that the evidence for each of the three neurobiological models of TD is mixed, in that all models receive (partial) support, and several studies provide support for multiple models. Because of large differences between studies in task design and analytical approach, it is difficult to draw a firm conclusion regarding which model provides the best explanation of the neural correlates of temporal discounting. We propose that some components of these models can complement each other, and future studies should test the predictions offered by different models against each other. Several future research directions are suggested, including studying the connectivity between brain regions in relation to discounting, and directly comparing the neural mechanisms involved in discounting of monetary and primary rewards. WIREs Cogn Sci 2013, 4:523-545. doi: 10.1002/wcs.1246 CONFLICT OF INTEREST: The authors have declared no conflicts of interest for this article. For further resources related to this article, please visit the WIREs website.

The interaction between reinforcement and inhibitory control in ADHD: A review and research guidelines

The majority of studies which have aimed to identify cognitive and motivational factors at play in ADHD have investigated cognitive-control processes and reinforcement effects in isolation. Notably, in recent years, the interaction between these two processes has been increasingly examined. Here, we aimed to provide a comprehensive and critical review of the behavioral and functional neuroimaging studies that have investigated reinforcement effects on inhibitory control in ADHD. The findings of our meta-analyses show that reinforcement can normalize inhibitory control in children and adolescents with ADHD to the baseline level of controls. Furthermore, the data suggests that inhibitory control may improve to a larger extent in youth with ADHD compared with controls, as a function of reinforcement. Based on (1) this review and meta-analyses, (2) functional neuroimaging studies in healthy populations, and (3) existing ADHD and neurobiological models of dual processes, we propose specific guidelines for future research, which are anticipated to further elucidate processes underlying impulsive behavior associated with ADHD.

New perspectives on self-control development: highlighting the role of intentional inhibition.

The ability to exert self-control over one׳s thoughts and actions is crucial for successful functioning in daily life. To date, self-control development has been primarily studied from the perspective of externally driven inhibition. In this review, we introduce a new perspective on the development of self-control by highlighting the importance of intentional inhibition. First, we will review the existing behavioral and neuroscientific literature on the development of self-control from the perspective of externally driven inhibition. Next, we will introduce a new framework for studying the development of self-control from the perspective of intentional inhibition. We will discuss several recent studies in this domain, showing that intentional inhibition within cold contexts has an early development, but continues to develop through adolescence in motivational contexts. We conclude that understanding the developmental trajectory of intentional inhibition in cold and motivationally relevant contexts and its underlying mechanisms is an important direction for future research, which has important implications for our understanding of developmental disorders associated with problems in self-control, such as Attention Deficit Hyperactivity Disorder.

Ventral striatal hyperconnectivity during rewarded interference control in adolescents with ADHD

OBJECTIVEnAttention-deficit/hyperactivity disorder (ADHD) is characterized by cognitive deficits (e.g., interference control) and altered reward processing. Cognitive control is influenced by incentive motivation and according to current theoretical models, ADHD is associated with abnormal interactions between incentive motivation and cognitive control. However, the neural mechanisms by which reward modulates cognitive control in individuals with ADHD are unknown.nnnMETHODnWe used event-related functional resonance imaging (fMRI) to study neural responses during a rewarded Stroop color-word task in adolescents (14-17 years) with ADHD (nxa0=xa025; 19 boys) and healthy controls (nxa0=xa033; 22 boys).nnnRESULTSnAdolescents with ADHD showed increased reward signaling within the superior frontal gyrus and ventral striatum (VS) relative to controls. Importantly, functional connectivity analyses revealed a hyperconnectivity between VS and motor control regions in the ADHD group, as a function of reward-cognitive control integration. Connectivity was associated with performance improvement in controls but not in the ADHD group, suggesting inefficient connectivity.nnnCONCLUSIONnAdolescents with ADHD show increased neural sensitivity to rewards and its interactions with interference control in VS and motor regions, respectively. The findings support theoretical models of altered reward-cognitive control integration in individuals with ADHD.

Measuring the Neural Basis of Reward Anticipation and Reward Receipt in Attention-Deficit/Hyperactivity Disorder: The Importance of Task Design

In the May 2015 issue of the Journal, von Rhein et al. investigated ventral-striatal (VS) response during monetary reward anticipation and receipt using an impressively large sample (N = 350) of adolescents and young adults with attention-deficit/hyperactivity disorder (ADHD), their unaffected siblings, and typically functioning controls. The goal was to resolve putative inconsistent findings in previous studies by using a statistically well-powered, multicenter, large-scale functional magnetic resonance imaging study.

The relation between procrastination and symptoms of attention-deficit hyperactivity disorder (ADHD) in undergraduate students.

Procrastination is defined as the tendency to delay activities that have to be completed before a deadline. It is often part of psychotherapies for adults with attention‐deficit hyperactivity disorder (ADHD). However, procrastination is officially not acknowledged as an ADHD‐related symptom. Therefore, little is known about the role of procrastination in ADHD. We investigated the relation between procrastination and ADHD‐related symptoms of inattention, hyperactivity, and impulsivity in 54 students with varying levels of self‐reported ADHD‐related behaviours. Various measures of procrastination were used, including questionnaires of academic, general procrastination and susceptibility to temptation as well as direct observation of academic procrastination while solving math problems. We expected a positive relation between severity of ADHD‐related behaviours and procrastination, specifically for impulsivity. However, partial correlations (corrected for the other symptom domain of ADHD) indicated that only inattention was correlated with general procrastination. This specific and preliminary finding can stimulate future research in individuals diagnosed with ADHD. Copyright

Neural mechanisms of individual differences in temporal discounting of monetary and primary rewards in adolescents

Abstract Adolescents are generally characterized as impulsive. However, impulsivity is a multi‐dimensional construct that involves multiple component processes. Which of these components contribute to adolescent impulsivity is currently unclear. This study focused on the neural mechanisms underlying individual differences in distinct components of temporal discounting (TD), i.e., the preference for smaller immediate rewards over larger delayed rewards. Participants were 58 adolescents (12–16 years‐old) who performed an fMRI TD task with both monetary and snack rewards. Using mixed‐effects modeling, we determined participants’ average impatience, and further decomposed TD choices into: 1) amount sensitivity (unique contribution of the magnitude of the immediate reward); and 2) delay sensitivity (unique contribution of delay duration). Adolescents’ average impatience was positively correlated with frontoparietal and ventral striatal activity during delayed reward choices, and with ventromedial prefrontal cortex activity during immediate reward choices. Adolescents’ amount sensitivity was positively associated with ventral striatal and dorsal anterior cingulate cortex activity during immediate reward choices. Delay sensitivity was positively correlated with inferior parietal cortex activity during delayed reward choices. As expected, snacks were discounted more steeply than money, and TD of both reward types was associated with overlapping activation in the inferior parietal cortex. Exploring whether testosterone or estradiol were associated with TD and its neural correlates revealed no significant associations. These findings indicate that distinct components contribute uniquely to TD choice and that individual differences in amount sensitivity are uniquely associated with activation of reward valuation areas, while individual differences in delay sensitivity are uniquely associated with activation of cognitive control areas. HighlightsWe examined individual differences in temporal discounting in adolescents.We determined adolescents’ average impatience and amount and delay sensitivity.Average impatience was positively associated with frontoparietal and striatal activity.Amount sensitivity was positively associated with ventral striatum activity.Delay sensitivity was positively associated with parietal cortex activity.

Planning to make economic decisions in the future, but choosing impulsively now: Are preference reversals related to symptoms of ADHD and depression?

A preference for smaller immediate rewards over larger delayed rewards (delay discounting, DD) is common in attention deficit hyperactivity disorder (ADHD), but rarely investigated in depression. Whether this preference is due to sensitivity to reward immediacy or delay aversion remains unclear. To investigate this, we examined whether ADHD and depressive symptoms are associated with preference reversals: a switch from smaller immediate rewards to larger delayed rewards when smaller rewards are also delayed. We also examined whether these symptoms differentially affect DD of losses. In Study 1 undergraduates completed a questionnaire about ADHD symptoms, and performed a hypothetical DD task. In the NOW condition, participants were presented with choices between a small reward available today and a large reward available after one year. In the FUTURE condition both rewards were delayed with +1 year. In Study 2 undergraduates completed questionnaires about ADHD and depressive symptoms and performed a DD task with gains and losses. Participants showed preference reversals in both studies and tasks. Losses were less steeply discounted than gains. ADHD and depressive symptoms did not influence these effects. Depressive symptoms, but not ADHD symptoms, were associated with less economic choices in general. These findings suggest that impulsive choice in depression is not explained by sensitivity to reward immediacy. Copyright