Domain-general and domain-specific aspects of temporal discounting in children with ADHD and autism spectrum disorders (ASD): a proof of concept study

ADHD and the Choice of Small Immediate Over Larger Delayed Rewards: A Comparative Meta-Analysis of Performance on Simple Choice-Delay and Temporal Discounting Paradigms

Objective: Impulsive choices can lead to suboptimal decision making, a tendency which is especially marked in individuals with ADHD. We compared two different paradigms assessing impulsive choice: the simple choice paradigm (SCP) and the temporal discounting paradigm (TDP). Method: Random effects meta-analyses on 37 group comparisons (22 SCP; 15 TDP) consisting of 3.763 participants (53% ADHD). Results: Small-to-medium effect sizes emerged for both paradigms, confirming that participants with ADHD choose small immediate over large delayed rewards more frequently than controls. Moderation analyses show that offering real rewards in the SCP almost doubled the odds ratio for participants with ADHD. Conclusion: We suggest that a stronger than normal aversion toward delay interacts with a demotivating effect of hypothetical rewards, both factors promoting impulsive choice in participants with ADHD. Furthermore, we suggest the SCP as the paradigm of choice due to its larger ecological validity, contextual sensitivity, and reliability.

A Systematic Review of the Positive Valence System in Autism Spectrum Disorder

This review synthesized current literature of behavioral and cognitive studies targeting reward processing in autism spectrum disorder (ASD). The National Institute of Mental Health's Research Domain Criteria (RDoC) Positive Valence System (PVS) domain was used as an overarching framework. The objectives were to determine which component operations of reward processing may be atypical in ASD and consequently postulate a heuristic model of reward processing in ASD that could be evaluated with future research. 34 studies were identified from the Embase, PubMed, PsycINFO, and Web of Science databases and included in the review using guidelines from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (also known as PRISMA guidelines). The extant literature suggested potential relationships between social symptoms of ASD and PVS sub-constructs of reward anticipation, probabilistic and reinforcement learning, reward prediction error, reward (probability), delay, and effort as well as between restricted and repetitive behaviors and interests (RRBIs) and PVS-sub constructs of initial response to reward, reward anticipation, reward (probability), delay, and effort. However, these findings are limited by a sparse and mixed literature for some sub-constructs. We put forward a developmentally informed heuristic model that posits how these component reward processes may be implicated in early ASD behaviors as well as later emerging and more intransigent symptoms. Future research is needed to comprehensively evaluate the proposed model.

Delay discounting of different outcomes: Review and theory

Steep delay discounting is characterized by a preference for small immediate outcomes relative to larger delayed outcomes and is predictive of drug abuse, risky sexual behaviors, and other maladaptive behaviors. Nancy M. Petry was a pioneer in delay discounting research who demonstrated that people discount delayed monetary gains less steeply than they discount substances with abuse liability. Subsequent research found steep discounting for not only drugs, but other nonmonetary outcomes such as food, sex, and health. In this systematic review, we evaluate the hypotheses proposed to explain differences in discounting as a function of the type of outcome and explore the trait- and state-like nature of delay discounting. We found overwhelming evidence for the state-like quality of delay discounting: Consistent with Petry and others' work, nonmonetary outcomes are discounted more steeply than monetary outcomes. We propose two hypotheses that together may account for this effect: Decreasing Future Preference and Decreasing Future Worth. We also found clear evidence that delay discounting has trait-like qualities: People who steeply discount monetary outcomes steeply discount nonmonetary outcomes as well. The implication is that changing delay discounting for one outcome could change discounting for other outcomes.

Childhood ADHD and Delayed Reinforcement: A Direct Comparison of Performance on Hypothetical and Real-Time Delay Tasks

Objective: Individuals with ADHD have been shown to prefer smaller sooner over larger later rewards. This has been explained in terms of abnormally steeper discounting of the value of delayed reinforcers. Evidence for this comes from different experimental paradigms. In some, participants experience delay in the laboratory (real-time delay tasks; R-TD), in others they imagine the delay to reinforcers (hypothetical delay tasks; HD). Method: We directly contrasted the performance of 7- to 12-year-old children with ADHD (n = 23) and matched controls (n = 23) on R-TD and HD tasks with monetary rewards. Results: Children with ADHD displayed steeper temporal discounting on the R-TD, but not the HD tasks. Conclusion: These findings suggest that the experience of waiting prior to the delivery of rewards is an important determinant of heightened temporal discounting in ADHD-a finding consistent with models that emphasize the aversive nature of delay for children.

Temporal Reward Discounting in Children with Attention Deficit/Hyperactivity Disorder (ADHD), and Children with Autism Spectrum Disorder (ASD): A Systematic Review

Children with ADHD and ASD may present differences in the affective-motivational processes. We systematically review the literature regarding temporal discounting in children up to 12 years with ADHD and ASD. Six articles were included, five studies with ADHD children (n = 231), one with ASD children (n = 21), all including typically developing children as controls (n = 210). Five studies (four with ADHD and one with ASD) found greater temporal reward discounting for clinical groups. Occurrence of ADHD appears to rush even more the decision-making process at this stage of development, but there is still a lack in the literature, especially evaluating individuals with ASD.

Social and delay discounting in autism spectrum disorder

Current literature is divided over whether and how processes such as perspective taking and reward sensitivity differ between individuals with autism spectrum disorder (ASD) versus neurotypical individuals. Discounting tasks may provide novel insight into how these processes operate. In delay discounting tasks, participants choose between smaller immediate rewards and larger delayed rewards, and in social discounting tasks, participants choose between a smaller monetary rewards for themselves versus a larger reward for partners of varied social distance (e.g., a close friend vs. an acquaintance). Delay and social discounting tasks thus implicitly measure the subjective value of rewards given to one's future self and to others, capturing constructs such as perspective taking, reward processing, and social closeness, all of which have been discussed as core cognitive mechanisms underlying ASD. Despite extensive research on discounting in other clinical populations, few studies have examined delay discounting in ASD and no research has examined social discounting in ASD. The goal of the current study was to assess delay and social discounting for monetary rewards in a single sample of adolescents and adults with ASD compared to a matched neurotypical sample. Overall, adults and adolescents with ASD valued both future rewards and rewards given to others less than their typical counterparts did, but rates of discounting were not significantly correlated across temporal and social domains. These results extend an important behavioral paradigm for understanding both perspective taking and reward processing to autism. Autism Res 2019, 12: 870-877. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Discounting tasks-which experimentally measure the subjective value of different rewards-have been used with a variety of clinical populations, but are underexplored in ASD. We found that compared to neurotypical individuals, individuals with ASD showed diminished subjective value for future rewards (compared to immediate rewards) and rewards for others (compared to rewards for self). This finding has implications for understanding perspective taking, reward processing, and social closeness in ASD.

Temporal discounting and attention-deficit/hyperactivity disorder in childhood: reasons for devising different tasks

INTRODUCTION

Temporal discounting (TD) describes how a certain reward is seen as less valuable the more its delivery is postponed. There are two main types of TD tasks, hypothetical and real, both of which use monetary rewards. Over the last few years, however, variants of these tasks have been adjusted to assess clinical groups of children showing impulsivity as found in attention-deficit/hyperactivity disorder (ADHD).

OBJECTIVE

To review and discuss studies conducted over the last 10 years on the use of TD tasks in the assessment of pediatric patients with ADHD.

METHOD

For this literature review, articles were non-systematically selected from PubMed, MEDLINE and SciELO databases to include experimental studies on the use of at least one TD paradigm to assess and distinguish ADHD and non-ADHD groups.

RESULTS

Of the studies assessed, 76.19% used hypothetical tasks, followed by real tasks (28.57%), and, finally, tasks using different types of reward, such as toys or rewarding activities (14.28%).

CONCLUSIONS

Although assessed in few studies, real and alternative tasks appeared to be effective in differentiating clinical groups and suitable for investigating hot executive functions in childhood.

Preference for Smaller Sooner Over Larger Later Rewards in ADHD: Contribution of Delay Duration and Paradigm Type

OBJECTIVE

Individuals with ADHD preferentially choose smaller sooner (SS) over larger later (LL) rewards, termed impulsive choice. This has been observed to different degrees on single-choice and more complex discounting tasks using various types of rewards and durations of delays. There has been no direct comparison of performance of ADHD children using these two paradigms.

METHOD

Two experimental paradigms, single-choice and temporal discounting, each including two delay conditions (13 and 25 s), were administered to 7- to 9-year-old children with ADHD ( n = 17) and matched controls ( n = 24).

RESULTS

Individuals with ADHD chose more SS rewards than controls on both tasks, but in the long delay condition only.

CONCLUSION

These findings demonstrate that delay durations rather than paradigm types determine laboratory-based measures of choice impulsivity in ADHD.

Subtyping cognitive profiles in Autism Spectrum Disorder using a Functional Random Forest algorithm

DSM-5 Autism Spectrum Disorder (ASD) comprises a set of neurodevelopmental disorders characterized by deficits in social communication and interaction and repetitive behaviors or restricted interests, and may both affect and be affected by multiple cognitive mechanisms. This study attempts to identify and characterize cognitive subtypes within the ASD population using our Functional Random Forest (FRF) machine learning classification model. This model trained a traditional random forest model on measures from seven tasks that reflect multiple levels of information processing. 47 ASD diagnosed and 58 typically developing (TD) children between the ages of 9 and 13 participated in this study. Our RF model was 72.7% accurate, with 80.7% specificity and 63.1% sensitivity. Using the random forest model, the FRF then measures the proximity of each subject to every other subject, generating a distance matrix between participants. This matrix is then used in a community detection algorithm to identify subgroups within the ASD and TD groups, and revealed 3 ASD and 4 TD putative subgroups with unique behavioral profiles. We then examined differences in functional brain systems between diagnostic groups and putative subgroups using resting-state functional connectivity magnetic resonance imaging (rsfcMRI). Chi-square tests revealed a significantly greater number of between group differences (p < .05) within the cingulo-opercular, visual, and default systems as well as differences in inter-system connections in the somato-motor, dorsal attention, and subcortical systems. Many of these differences were primarily driven by specific subgroups suggesting that our method could potentially parse the variation in brain mechanisms affected by ASD.

Comparison of neural substrates of temporal discounting between youth with autism spectrum disorder and with obsessive-compulsive disorder

BACKGROUND

Autism spectrum disorder (ASD) and obsessive-compulsive disorder (OCD) share abnormalities in hot executive functions such as reward-based decision-making, as measured in the temporal discounting task (TD). No studies, however, have directly compared these disorders to investigate common/distinct neural profiles underlying such abnormalities. We wanted to test whether reward-based decision-making is a shared transdiagnostic feature of both disorders with similar neurofunctional substrates or whether it is a shared phenotype with disorder-differential neurofunctional underpinnings.

METHODS

Age and IQ-matched boys with ASD (N = 20), with OCD (N = 20) and 20 healthy controls, performed an individually-adjusted functional magnetic resonance imaging (fMRI) TD task. Brain activation and performance were compared between groups.

RESULTS

Boys with ASD showed greater choice-impulsivity than OCD and control boys. Whole-brain between-group comparison revealed shared reductions in ASD and OCD relative to control boys for delayed-immediate choices in right ventromedial/lateral orbitofrontal cortex extending into medial/inferior prefrontal cortex, and in cerebellum, posterior cingulate and precuneus. For immediate-delayed choices, patients relative to controls showed reduced activation in anterior cingulate/ventromedial prefrontal cortex reaching into left caudate, which, at a trend level, was more decreased in ASD than OCD patients, and in bilateral temporal and inferior parietal regions.

CONCLUSIONS

This first fMRI comparison between youth with ASD and with OCD, using a reward-based decision-making task, shows predominantly shared neurofunctional abnormalities during TD in key ventromedial, orbital- and inferior fronto-striatal, temporo-parietal and cerebellar regions of temporal foresight and reward processing, suggesting trans-diagnostic neurofunctional deficits.

Temporal discounting and emotional self-regulation in children with attention-deficit/hyperactivity disorder

Temporal Discounting (TD) reflects a tendency to discount a reward more deeply the longer its delivery is delayed. TD tasks and behavioral scales have been used to investigate 'hot' executive functions in ADHD. The present study analyzed TD task performance shown by ADHD and control groups for correlations with emotional self-regulation metrics from two scales, the Behavior Rating Inventory of Executive Functions (BRIEF) and the Child Behavior Checklist (CBCL). Children (ages 8-12) with ADHD (n=25) and controls (n=24) were assessed using material rewards (toys) for three types of task: Hypothetical (H); Hypothetical with temporal expectation (HTE); and Real (R). Between-group differences were found for the HTE task, on which the ADHD group showed a higher rate of discounting their favorite toy over time, especially at 10s and 20s. This was the only task on which performance significantly correlated with BRIEF metrics, thus suggesting associations between impulsivity and low emotional self-regulation, but no task was correlated with CBCL score. The conclusion is that tasks involving toys and HTE in particular may be used to investigate TD in children with ADHD and as a means of evaluating the interface between the reward system and emotional self-regulation.

Investigating the Impact of Cognitive Load and Motivation on Response Control in Relation to Delay Discounting in Children with ADHD

Attention-deficit/hyperactivity disorder (ADHD) is characterized by deficits in impulse control across a range of behaviors, from simple actions to those involving complex decision-making (e.g., preference for smaller-sooner versus larger later rewards). This study investigated whether changes in motor response control with increased cognitive load and motivational contingencies are associated with decision-making in the form of delay discounting among 8-12 year old children with and without ADHD. Children with ADHD (n = 26; 8 girls) and typically developing controls (n = 40; 11 girls) completed a standard go/no-go (GNG) task, a GNG task with motivational contingencies, a GNG task with increased cognitive load, and two measures of delay discounting: a real-time task in which the delays and immediately consumable rewards are experienced in real-time, and a classic task involving choices about money at longer delays. Children with ADHD, particularly girls, exhibited greater delay discounting than controls during the real-time discounting task, whereas diagnostic groups did not significantly differ on the classic discounting task. The effect of cognitive load on response control was uniquely associated with greater discounting on the real-time task for children with ADHD, but not for control children. The effect of motivational contingencies on response control was not significantly associated with delay discounting for either diagnostic group. The findings from this study help to inform our understanding of the factors that influence deficient self-control in ADHD, suggesting that impairments in cognitive control may contribute to greater delay discounting in ADHD.

Attention-Deficit/Hyperactivity Disorder and Monetary Delay Discounting: A Meta-Analysis of Case-Control Studies

BACKGROUND

A growing number of studies have investigated delay discounting, a behavioral economic index of impulsivity, and its relevance to attention deficit hyperactivity disorder (ADHD), but with mixed findings. The current meta-analysis synthesizes the literature on the relationship between monetary delay discounting and ADHD in studies using case-control designs. Specifically, the objectives were: 1) to characterize the aggregated differences in monetary delay discounting between individuals with ADHD (cases) and controls in studies using categorical case-control designs; 2) to examine potential differences based on sample age (<18 vs. >18), reward outcome (real vs. hypothetical), and prevalence of conduct disorder and oppositional defiant disorder in the sample; and 3) to evaluate potential small-study (publication) bias in the literature.

METHODS

From 567 candidate articles, 21 independent investigations yielded 25 case-control comparisons (total N=3,913). Random effects meta-analysis was conducted using Cohen's d as the common effect size. Publication bias was evaluated using fail-safe N, Begg-Mazumdar and Egger tests, and metaregression of publication year and effect size.

RESULTS

Across studies, a statistically significant difference of medium magnitude effect size was present for the case-control comparisons (d=0.43; p < 10-15). No significant differences based on sample age, reward outcome, or comorbid status was detected. Minimal heterogeneity and evidence of publication bias was present.

CONCLUSIONS

These findings provide robust evidence that delay discounting is significantly elevated among individuals with ADHD compared to controls. Gaps in the literature and the importance of characterizing the neural and genetic bases of this relationship are discussed.

An update on the comorbidity of ADHD and ASD: a focus on clinical management

Attention deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) commonly co-occur. With the DSM-5, clinicians are permitted to make an ASD diagnosis in the context of ADHD. In earlier versions of the DSM, this was not acceptable. Both ASD and ADHD are reported to have had substantial increases in prevalence within the past 10 years. As a function of both the increased prevalence of both disorders as well as the ability to make an ASD diagnosis in ADHD, there has been a significant amount of research focusing on the comorbidity between ADHD and ASD in the past few years. Here, we provide an update on the biological, cognitive and behavioral overlap/distinctiveness between the two neurodevelopmental disorders with a focus on data published in the last four years. Treatment strategies for the comorbid condition as well as future areas of research and clinical need are discussed.

Increased Delay Discounting on a Novel Real-Time Task among Girls, but not Boys, with ADHD

The aim of this study was to examine delay discounting in girls and boys with ADHD-Combined type (ADHD-C) relative to typically developing (TD) children on two tasks that differ in the extent to which the rewards and delays were experienced by participants. Children ages 8-12 years with ADHD-C (n=65; 19 girls) and TD controls (n=55; 15 girls) completed two delay discounting tasks involving a series of choices between smaller, immediate and larger, delayed rewards. The classic delay discounting task involved choices about money at delays of 1-90 days and only some of the outcomes were actually experienced by the participants. The novel real-time discounting task involved choices about an immediately consumable reward (playing a preferred game) at delays of 25-100 s, all of which were actually experienced by participants. Participants also provided subjective ratings of how much they liked playing the game and waiting to play. Girls with ADHD-C displayed greater delay discounting compared to boys with ADHD-C and TD girls and boys on the real-time discounting task. Diagnostic group differences were not evident on the classic discounting task. In addition, children with ADHD-C reported wanting to play the game more and liking waiting to play the game less than TD children. This novel demonstration of greater delay discounting among girls with ADHD-C on a discounting task in which the rewards are immediately consumable and the delays are experienced in real-time informs our understanding of sex differences and motivational processes in children with ADHD. (JINS, 2016, 22, 12-23).

Myopic decisions under negative emotions correlate with altered time perception

Previous studies have obtained inconsistent findings about emotional influence on inter-temporal choice (IC). In the present study, we first examined the effect of temporary emotional priming induced by affective pictures in a trial-to-trial paradigm on IC. The results showed that negative priming resulted in much higher percentages of trials during which smaller-but-sooner reward (SS%) were chosen compared with positive and neutral priming. Next, we attempted to explore the possible mechanisms underlying such emotional effects. When participants performed a time reproduction task, mean reaction times in negative priming condition were significantly shorter than those in the other two emotional contexts, which indicated that negative emotional priming led to overestimation of time. Moreover, such overestimation was negatively correlated with performance in the IC task. In contrast, temporary changes of emotional contexts did not alter performances in a Go/NoGo task (including commission errors and omission errors). In sum, our present findings suggested that myopic decisions under negative emotions were associated with altered time perception but not response inhibition.

The role of simulation in intertemporal choices

One route to understanding the thoughts and feelings of others is by mentally putting one's self in their shoes and seeing the world from their perspective, i.e., by simulation. Simulation is potentially used not only for inferring how others feel, but also for predicting how we ourselves will feel in the future. For instance, one might judge the worth of a future reward by simulating how much it will eventually be enjoyed. In intertemporal choices between smaller immediate and larger delayed rewards, it is observed that as the length of delay increases, delayed rewards lose subjective value; a phenomenon known as temporal discounting. In this article, we develop a theoretical framework for the proposition that simulation mechanisms involved in empathizing with others also underlie intertemporal choices. This framework yields a testable psychological account of temporal discounting based on simulation. Such an account, if experimentally validated, could have important implications for how simulation mechanisms are investigated, and makes predictions about special populations characterized by putative deficits in simulating others.

Differentiating neural reward responsiveness in autism versus ADHD

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Brain responsiveness to social and monetary reward were studied in ADHD versus ASD.

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Clinical groups versus TDC had different ventral striatum activation to both rewards.

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Medial prefrontal overactivation in response to social reward was ADHD specific.

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Ventral striatal underactivation in response to monetary reward was ASD specific.

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Fronto-striato-parietal underactivation for money was shared by both clinical groups.

Although attention deficit hyperactivity disorders (ADHD) and autism spectrum disorders (ASD) share certain neurocognitive characteristics, it has been hypothesized to differentiate the two disorders based on their brain's reward responsiveness to either social or monetary reward. Thus, the present fMRI study investigated neural activation in response to both reward types in age and IQ-matched boys with ADHD versus ASD relative to typically controls (TDC). A significant group by reward type interaction effect emerged in the ventral striatum with greater activation to monetary versus social reward only in TDC, whereas subjects with ADHD responded equally strong to both reward types, and subjects with ASD showed low striatal reactivity across both reward conditions. Moreover, disorder-specific neural abnormalities were revealed, including medial prefrontal hyperactivation in response to social reward in ADHD versus ventral striatal hypoactivation in response to monetary reward in ASD. Shared dysfunction was characterized by fronto-striato-parietal hypoactivation in both clinical groups when money was at stake. Interestingly, lower neural activation within parietal circuitry was associated with higher autistic traits across the entire study sample. In sum, the present findings concur with the assumption that both ASD and ADHD display distinct and shared neural dysfunction in response to reward.

Responsivity to familiar versus unfamiliar social reward in children with autism

In autism spectrum disorders (ASD), social motivation theories suggest that the core social communication problems seen in children with ASD arise from diminished responsiveness to social reward. Although clinical and experimental data support these theories, the extent to which the reward deficit in ASD is unique for social rewards remains unclear. With the present investigation, we aimed to provide insight into the degree to which sociality as well as familiarity of reward incentives impact motivated goal-directed behavior in children with ASD. To do so, we directly compared the influence of familiar versus unfamiliar social reward relative to nonsocial, monetary reward in children with ASD relative to age- and IQ-matched typically developing controls (TDC) using a visual and auditory incentive go/nogo task with reward contingencies for successful response inhibitions. We found that children with ASD responded stronger to visual familiar and unfamiliar social reward as well as to nonsocial, monetary reward than TDC. While the present data are at odds with predictions made by social motivation theories, individual variations beyond clinical diagnosis, such as reward exposure across various social settings, help explain the pattern of results. The findings of this study stress the necessity for additional research on intra-individual as well as environmental factors that contribute to social reward responsiveness in individuals with ASD versus other neuropsychiatric disorders such as ADHD or conduct disorder.