Steep temporal reward discounting in ADHD-Combined type: Acting upon feelings

Difficulty waiting plays a primary role in symptoms of attention-deficit/hyperactivity disorder (ADHD), in particular, impulsivity. Current theories suggest that relatively strong preferences for small immediate rewards as observed in ADHD-Combined type are the result of delay-related negative feelings. However, the measurement of difficulty waiting is typically limited to objective choices between small immediate and large delayed rewards. This study aimed at extending the measurement of difficulty waiting in ADHD-Combined type with ratings about subjective feelings. Children and adolescents (ages 6-17) with ADHD-Combined type (n=25), ADHD-Inattentive type (n=20) and matched typically developing participants (n=37) performed temporal reward discounting tasks, and completed a Visual Analogue Scale of subjectively experienced ease/difficulty waiting. Although those with ADHD-Combined type demonstrated relatively steep temporal reward discounting, as reported elsewhere ( Scheres et al., 2010), there were no group differences for subjectively experienced ease/difficulty waiting. Additionally, correlations between subjective and objective measures of difficulty waiting were significantly higher in the ADHD-Combined type group than in the control group. These findings suggest that (a) those with ADHD-Combined type do not choose impulsively because they have more negative feelings about waiting than controls; (b) choices in the ADHD-Combined type group are more in accordance with/driven by their feelings than choices made by participants in the control group.     

Discounting preferences and response consistency as markers of functional ability in community-dwelling older adults

Introduction: Predictors of functional independence in older adults are in need. Based on findings that delay discounting, probability discounting, and the ability to respond consistently use cognitive abilities and neural systems with central relevance to functional ability, the present study evaluated whether these behavioral economic variables account for variance in everyday functioning in older adults. It was hypothesized that greater preference for immediate/probabilistic rewards and response inconsistency would independently predict decrements in instrumental activities of daily living (IADLs). Method: Participants included 64 community-dwelling older adults (65–85 years; mean age = 76.25 years; 76.60% female). Exclusionary criteria were neurological illness, illiteracy, substance dependence within the past 5 years, score of ≤20 on the Mini-Mental State Examination, and/or presence of dementia. Delay/probability discounting tasks consisted of a series of dichotomous selections between smaller, immediate/guaranteed and larger, delayed/probabilistic monetary values. Area under the curve (AUC) was used to index levels of discounting, while response (in)consistency was based on the percentage of contradictory responses. The Direct Assessment of Functional Status–Revised (DAFS–R) provided a performance-based assessment of IADLs. Hierarchical regression analyses were conducted to determine whether discounting preferences and response consistency accounted for variance in functional ability over and above relevant demographic characteristics. Results: Demographic characteristics accounted for significance variance in IADLs (p = .001, R² = .237). Probability discounting AUC (p = .014, ΔR² = .075) and response (in)consistency (p = .046, ΔR² = .050) each accounted for significant additional variance in functional ability, as did delay discounting response (in)consistency (p = .010, ΔR² = .081). Delay discounting AUC did not add significantly to the model (p = .861). Conclusions: Discounting preferences and choice consistency hold potential to serve as relatively fast and inexpensive markers of functional decline, likely due to neurocognitive deterioration relevant to both behavioral economic decision making and functional independence.     

Temporal reward discounting and ADHD: task and symptom specific effects

Summary This study investigated a new aspect of the association between ADHD symptoms and delay aversion. Participants were 55 undergraduate Psychology students with varying levels of self-reported ADHD symptoms. Various delay aversion tasks were used, including real and hypothetical temporal discounting tasks previously used in the field of ADHD. ADHD symptoms, specifically hyperactivity/impulsivity, were associated with steep discounting, but only when rewards and delays were real. These data suggest that (1) real temporal discounting tasks are more sensitive to ADHD-related delay aversion than hypothetical ones; (2) delay aversion may be a causal mechanism specifically associated with ADHD-Combined and Hyperactive/Impulsive Types but not Inattentive Type. These findings may help refine behavioral treatment approaches and models of ADHD. Correspondence: Anouk Scheres, Psychology Department, University of Arizona, 1503 E, University Blvd., Tucson, AZ 85721, USA     

Discounting of restraint usage,problem behavior management,and risk of autism severity

The current study examined whether a history of experience with children with autism affected the rate of discounting of a delayed or probable consequence. Experiment 1 utilized a temporal discounting task to compare the discounting rates of adults who have worked in an autism service setting and have experience with physical restraints to that of adults who have little or no experience with these populations. The results showed that adults with a history of contact with autism made less optimal choices and discounted restraint responsibilities more steeply than adults with no such history, indicating increased avoidance of engaging in restraints. Experiment 2 investigated how the same groups discounted child problem behavior, and showed that those with experience with autism preferred to delay working with children with severe problem behavior and discounted the student's problem behavior more steeply, again demonstrating increased avoidance. Experiment 3 examined risk tendencies in relation to having children with diminished functioning in parents who have children with autism and those who have only worked with them. Results showed that parents made riskier choices than non-parents. Overall, all 3 experiments showed that those with increased experience with children with autism tended toward more impulsive and risky choices.     

Prefrontal cortical–striatal dopamine receptor mRNA expression predicts distinct forms of impulsivity

Variation in dopamine receptor levels has been associated with different facets of impulsivity. To further delineate the neural substrates underlying impulsive action (inability to withhold a prepotent motor response) and impulsive choice (delay aversion), we characterised rats in the Differential Reinforcement of Low Rates of Responding task and a delay discounting task. We also measured performance on an effort‐based discounting task. We then assessed D1 and D2 dopamine receptor mRNA expression in subregions of the prefrontal cortex and nucleus accumbens using in situ hybridisation, and compared these data with behavioral performance. Expression of D1 and D2 receptor mRNA in distinct brain regions was predictive of impulsive action. A dissociation within the nucleus accumbens was observed between subregions and receptor subtypes; higher D1 mRNA expression in the shell predicted greater impulsive action, whereas lower D2 mRNA expression in the core predicted greater impulsive action. We also observed a negative correlation between impulsive action and D2 mRNA expression in the prelimbic cortex. Interestingly, a similar relationship was present between impulsive choice and prelimbic cortex D2 mRNA, despite the fact that behavioral indices of impulsive action and impulsive choice were uncorrelated. Finally, we found that both high D1 mRNA expression in the insular cortex and low D2 mRNA expression in the infralimbic cortex were associated with willingness to exert effort for rewards. Notably, dopamine receptor mRNA in these regions was not associated with either facet of impulsivity. The data presented here provide novel molecular and neuroanatomical distinctions between different forms of impulsivity, as well as effort‐based decision‐making.     

Decision-making on an explicit risk-taking task in preadolescents with attention-deficit/hyperactivity disorder

Summary. Inappropriate risk-taking and disadvantageous decision-making have been described as major behavioural characteristics of patients with attention-deficit/hyperactivity disorder (ADHD). However these behaviours are difficult to measure in laboratory contexts and recent studies have yielded inconsistent results which might be related to task characteristics. The present study adopted the Game of Dice Task, a test procedure in which risks are made explicit and the load on working memory is minimal. As a result, preadolescents with ADHD (N = 23) made significantly more risky choices and suffered major losses of money compared to normal controls (N = 24) but only when they played the game a second time. Differences in risk-taking correlated significantly with hyperactivity as rated by parents and with inhibitory control, but not with working memory performance. The results are discussed in the context of current theories of ADHD. Correspondence: Renate Drechsler, Department of Child and Adolescent Psychiatry, University of Zurich, Neumuensterallee 9, 8032 Zurich, Switzerland     

The medial temporal lobes are critical for reward‐based decision making under conditions that promote episodic future thinking

In the present study, we investigated the effect of medial temporal lobe (MTL) damage on human decision making in the context of reward‐based intertemporal choice. During intertemporal choice, humans typically devalue (or discount) a future reward to account for its delayed arrival (e.g., preferring $30 now over $42 in 2 months), but this effect is attenuated when participants engage in episodic future thinking, i.e., project themselves into the future to imagine a specific event. We hypothesized that this attenuation would be selectively impaired in amnesic patients, who have deficits in episodic future thinking. Replicating previous work, in a standard intertemporal choice task, amnesic patients showed temporal discounting indices similar to healthy controls. Consistent with our hypothesis, while healthy controls demonstrated attenuated temporal discounting in a condition that required participants first to engage in episodic future thinking (e.g., to imagine spending $42 at a theatre in 2 months), amnesic patients failed to demonstrate this effect. Moreover, as expected, amnesic patients' narratives were less episodically rich than those of controls. These findings extend the range of tasks that are shown to be MTL dependent to include not only memory‐based decision‐making tasks but also future‐oriented ones. © 2014 Wiley Periodicals, Inc.     

Studying the relation between temporal reward discounting tasks used in populations with ADHD: A factor analysis

Background: This study aimed at investigating the relationship between tasks that have been used in attention deficit hyperactivity disorder (ADHD) to measure choices between smaller immediate and larger delayed rewards: real and hypothetical temporal discounting tasks, and single‐choice paradigms. Methods: Participants were 55 undergraduate psychology students. Tasks included a real and hypothetical version of a temporal discounting (TD) task with choices between a large reward (10 cents) after delays up to 60 seconds, and smaller immediate rewards (2–8 cents); two versions of a hypothetical temporal discounting task with choices between a large reward ($100) after delays up to 120 months, and smaller immediate rewards ($1–$95); a Choice Delay Task with choices between one point now and two points after 30 seconds (one point is worth five cents). Results: Correlation analyses showed that the real and the hypothetical TD tasks with 10 cents were very strongly associated. However, the hypothetical TD tasks with $100 did not correlate with either the real or the hypothetical TD task with 10 cents. Principal component analysis extracted two components: one for small amounts and short delays, and a second one for large rewards and long delays. Conclusions: Temporal reward discounting is not a uniform construct. Functional brain imaging research could shed more light on unique brain activation patterns associated with different forms of temporal reward discounting. Copyright © 2010 John Wiley & Sons, Ltd.     

Temporal and probabilistic discounting of rewards in children and adolescents: effects of age and ADHD symptoms

This study investigated whether age and ADHD symptoms affected choice preferences in children and adolescents when they chose between (1) small immediate rewards and larger delayed rewards and (2) small certain rewards and larger probabilistic uncertain rewards. A temporal discounting (TD) task and a probabilistic discounting (PD) task were used to measure the degree to which the subjective value of a large reward decreased as one had to wait longer for it (TD), and as the probability of obtaining it decreased (PD). Rewards used were small amounts of money. In the TD task, the large reward (10 cents) was delayed by between 0 and 30s, and the immediate reward varied in magnitude (0-10 cents). In the PD task, receipt of the large reward (10 cents) varied in likelihood, with probabilities of 0, 0.25, 0.5, 0.75, and 1.0 used, and the certain reward varied in magnitude (0-10 cents). Age and diagnostic group did not affect the degree of PD of rewards: All participants made choices so that total gains were maximized. As predicted, young children, aged 6-11 years (n = 25) demonstrated steeper TD of rewards than adolescents, aged 12-17 years (n = 21). This effect remained significant even when choosing the immediate reward did not shorten overall task duration. This, together with the lack of interaction between TD task version and age, suggests that steeper discounting in young children is driven by reward immediacy and not by delay aversion. Contrary to our predictions, participants with ADHD (n = 22) did not demonstrate steeper TD of rewards than controls (n = 24). These results raise the possibility that strong preferences for small immediate rewards in ADHD, as found in previous research, depend on factors such as total maximum gain and the use of fixed versus varied delay durations. The decrease in TD as observed in adolescents compared to children may be related to developmental changes in the (dorsolateral) prefrontal cortex. Future research needs to investigate these possibilities.     

Delayed reward discounting and increased risk for suicide attempts among U.S. adults with probable PTSD

BackgroundPTSD is an established risk factor for suicide attempts and suicide death, but the mechanisms underlying this association remain unknown. The present study examined associations among delayed reward discounting—the balance between smaller immediate available rewards versus larger delayed rewards—self-reported PTSD symptoms, and recent suicide attempts among individuals reporting suicide ideation within the past year.MethodsA cross-sectional survey of U.S. adults completed the Primary Care PTSD Screen for DSM-5, the 21-item Monetary Choice Questionnaire, and the Self-Injurious Thoughts and Behaviors Interview-Revised. Analyses of variance and multinomial regression models were used to test associations among variables.ResultsAmong participants reporting suicide ideation within the past year, discount rates were significantly higher among those reporting more PTSD symptoms and a past-year suicide attempt, suggesting these participants expressed a preference for immediately available rewards.ConclusionsChoice behavior among individuals reporting many PTSD symptoms and a recent suicide attempt is influenced to a greater degree by immediately available rewards. Sensitivity to immediate rewards at the expense of larger delayed rewards may reflect a vulnerability for suicidal behavior among individuals screening positive for PTSD.     

Neural correlates of choice behavior related to impulsivity and venturesomeness

Impulsivity has been associated with several psychiatric disorders including drug addiction and gambling. Impulsive subjects typically have a preference for short-term over long-term rewards and make risky choices. This study used functional magnetic resonance imaging (fMRI) to investigate the neural correlates of self-rated impulsivity and venturesomeness during tasks involving delayed and risky choice. A broader sampling approach was taken by recruiting participants with behaviors that have been linked to impulsivity (gambling N = 15, and recreational drug use N = 10) and those without these behaviors (N = 9). Selection between delayed or probabilistic rewards was associated with activation in fronto-parietal regions in line with previous research. When selecting between delayed rewards, activity within the pregenual anterior cingulate cortex and ventrolateral prefrontal cortex correlated positively with impulsivity scores while activity within the orbitofrontal cortex, subgenual anterior cingulate cortex and caudate correlated positively with venturesomeness scores. Selection between probabilistic rewards revealed no correlation between scores and regional activations. The results from this study provide targets for future research investigating the neural substrates of impulsivity. They also provide targets for the further investigation into the pathophysiology of addiction and impulse-control disorders.     

Delay discounting and neurocognitive correlates among inner city adolescents with and without family history of substance use disorder

Adolescents with a family history (FH+) of substance use disorder (SUD) are at a greater risk for SUD, suggested to be partly due to the transmission of behavioral impulsivity. We used a delay discounting task to compare impulsivity in decision-making and its associated brain functioning among FH+ and FH - minority adolescents. Participants chose between Smaller Sooner (SS) and Larger Later (LL) rewards. The SS was available immediately (Now trials) or in the future (Not-Now trials), allowing for greater differentiation between impulsive decisions. The FH+ group showed greater impatience by responding SS more frequently than the FH - group, only on the Now trials, and even when the relative reward differences (RRD) increased. Surprisingly, there were no differences in brain activity between the groups. Combined, the groups showed greater reward activity during the Now vs. Not-Now trials in medial prefrontal/anterior cingulate, posterior cingulate, precuneus, and inferior frontal gyrus (i.e., an immediacy effect). As the RRD increased activation in the reward network decreased, including the striatum, possibly reflecting easy decision-making. These results indicate that risk for SUD, seen behaviorally among FH+ adolescents, may not yet be associated with discernable brain changes, suggesting that early intervention has the potential to reduce this risk.     

Ventral striatal activity links adversity and reward processing in children

Adversity impacts many aspects of psychological and physical development including reward-based learning and decision-making. Mechanisms relating adversity and reward processing in children, however, remain unclear. Here, we show that adversity is associated with potentiated learning from positive outcomes and impulsive decision-making, but unrelated to learning from negative outcomes. We then show via functional magnetic resonance imaging that the link between adversity and reward processing is partially mediated by differences in ventral striatal response to rewards. The findings suggest that early-life adversity is associated with alterations in the brain’s sensitivity to rewards accounting, in part, for the link between adversity and altered reward processing in children.     

Toward noninvasive monitoring of ongoing electrical activity of human uterus and fetal heart and brain

Objective

To evaluate whether a full-coverage fetal-maternal scanner can noninvasively monitor ongoing electrophysiological activity of maternal and fetal organs.

Temporal discounting for self and friends in adolescence: A fMRI study

Adolescence is characterized by impulsivity but also by increased importance of friendships. This study took the novel perspective of testing temporal discounting in a fMRI task where choices could affect outcomes for 96 adolescents (aged 10–20-years) themselves and their best friend. Decisions either benefitted themselves (i.e., the Self Immediate – Self Delay’ condition) or their friend (i.e., ‘Friend Immediate – Friend Delay’ condition); or juxtaposed rewards for themselves and their friends (i.e., the ‘Self Immediate – Friend Delay’ or ‘Friend Immediate – Self Delay’ conditions). We observed that younger adolescents were more impulsive; and all participants were more impulsive when this was associated with an immediate benefit for friends. Individual differences analyses revealed increased activity in the subgenual anterior cingulate cortex extending in the ventral striatum for immediate relative to delayed reward choices for self. Temporal choices were associated with activity in the prefrontal cortex, parietal cortex, insula, and ventral striatum, but only activity in the right inferior parietal lobe was associated with age. Finally, temporal delay choices for friends relative to self were associated with increased activity in the temporo-parietal junction and precuneus. Overall, this study shows a unique role of the social context in adolescents’ temporal decision making.     

Adolescent methylmercury exposure affects choice and delay discounting in mice

The developing fetus is vulnerable to low-level exposure to methylmercury (MeHg), an environmental neurotoxicant, but the consequences of exposure during the adolescent period remain virtually unknown. The current experiments were designed to assess the effects of low-level MeHg exposure during adolescence on delay discounting, preference for small, immediate reinforcers over large, delayed ones, using a mouse model. Thirty-six male C57BL/6n mice were exposed to 0, 0.3, or 3.0 ppm mercury (as MeHg) via drinking water from postnatal day 21 through 59, encompassing the murine adolescent period. As adults, mice lever pressed for a 0.01-cc droplet of milk solution delivered immediately or four 0.01-cc droplets delivered after a delay. Delays ranged from 1.26 to 70.79 s, and all were presented within a session. A model based on the Generalized Matching Law indicated that sensitivity to reinforcer magnitude was lower for MeHg-exposed mice relative to controls, indicating that responding in MeHg-exposed mice was relatively indifferent to the larger reinforcer. Sensitivity to reinforcer delay was reduced (delay discounting was decreased) in the 0.3-ppm group, but not in the 3.0-ppm group, compared to controls. Adolescence is a developmental period during which the brain and behavior may be vulnerable to MeHg exposure. As with gestational MeHg exposure, the effects are reflected in the impact of reinforcing stimuli.