Impulsive decision-making and gambling severity: The influence of γ-amino-butyric acid (GABA) and glutamate-glutamine (Glx)

Discounting larger, delayed rewards for smaller, immediate rewards is a stable psychological trait known to be impaired in gambling disorder (GD). Neuroimaging with non-GD populations indicates involvement of anterior cingulate (ACC) and dorsolateral prefrontal cortex (dlPFC) in delay discounting. However, little is known about the role of intrinsic properties of brain functioning, such as neurotransmitter action, in impaired discounting in GD. Here, we used magnetic resonance spectroscopy to assess glutamate-glutamine (Glx) and γ-amino-butyric acid (GABA+) concentrations in the dorsal ACC (dACC), dlPFC and occipital cortex of human males with and without GD. Gambling symptom severity correlated negatively with Glx levels in the dACC and occipital voxels. Discounting of small and medium delayed rewards was negatively associated with GABA+ in the dACC, while the discounting of large delayed rewards was negatively associated with GABA+/Glx ratios in the dlPFC. Additionally, in GD, discounting of large delayed rewards was negatively correlated with occipital GABA+ levels. Overall, these findings show that high gambling symptom severity is associated with low levels of Glx and that dACC (GABA+), right dlPFC (GABA+/Glx), and occipital areas (GABA+) track the magnitude of delayed rewards during discounting.

Uncommitted Commitment: Behavioral Strategy to Prevent Preference Reversals

When both smaller-sooner (SS) and larger-later (LL) rewards are temporally distal, individuals frequently prefer the LL. However, because both outcomes become proximal, individuals frequently switch to preferring the SS. These preference reversals are predicted by hyperbolic delay discounting, and may model the essential challenge of self-control. Using smokers, a population known to have high rates of delay discounting, and thus more vulnerable to preference reversals, this pilot study sought to examine soft commitment as a strategy that may prevent preference reversals. Eleven smokers were assigned to an experimental commitment condition, operationalized as 3 weeks of daily commitment trials indicating preference between an SS and LL. Ten smokers were assigned to a control commitment condition. These 3 weeks were followed by 8 days of daily choice trials indicating preference between an impending SS and LL, for both experimental and control conditions. Though no overall difference of preference was observed between groups during the choice trials, hierarchical linear modeling revealed a decrease in preference for the LL over time by the control group (e.g., increasing trend of preference reversals) but no changes by the experimental group. This pilot study provides an initial indication that soft commitment can facilitate choice persistence and prevent preference reversals.

Brain functional connectome-based prediction of individual decision impulsivity

Extensive neuroimaging research has attempted to identify neural correlates and predictors of decision impulsivity. However, the nature and extent of decision impulsivity-brain association have varied substantially across studies, likely due to small sample sizes, limited image quality, different imaging measurement selections, and non-specific methodologies. The objective of this study was to develop a reliable predictive model of decision impulsivity-brain relationship in a large sample by applying connectome-based predictive modeling (CPM), a recently developed machine learning approach, to whole-brain functional connectivity data ("neural fingerprints"). For 809 healthy young participants from the Human Connectome Project, high-quality resting-state functional MRI data were utilized to construct brain functional connectome and delay discounting test was used to assess decision impulsivity. Then, CPM with leave-one-out cross-validation was conducted to predict individual decision impulsivity from whole-brain functional connectivity. We found that CPM successfully and reliably predicted the delay discounting scores in novel individuals. Moreover, different feature selection thresholds, parcellation strategies and cross-validation approaches did not significantly influence the prediction results. At the neural level, we observed that the decision impulsivity-associated functional networks included brain regions within default-mode, subcortical, somato-motor, dorsal attention, and visual systems, suggesting that decision impulsivity emerges from highly integrated connections involving multiple intrinsic networks. Our findings not only may expand existing knowledge regarding the neural mechanism of decision impulsivity, but also may present a workable route towards translation of brain imaging findings into real-world economic decision-making.

Delay discounting abnormalities are seen in first-episode schizophrenia but not in bipolar disorder

Delay discounting (DD) is the phenomenon of individuals discounting future rewards as a function of time. It has been studied extensively in chronic schizophrenia (SZ) and the results of these studies have been variable. Comorbidity in chronic samples could be one reason for the mixed findings and studies in first-episode (FE) samples are surprisingly lacking. Bipolar disorder (BP) which shares some genetic and symptom features with SZ could serve as an interesting comparison group for DD but has been underexplored. Here we present the first study that combines FE SZ, FE BP with psychotic features, as well as healthy controls and study DD with two versions of the task. We found that SZ showed steeper discounting than HC and BP on the well-validated Kirby DD task. SZ showed no difference than HC on a separate DD task with smaller rewards presented with decimal places and shorter delays. As a preliminary finding, DD was found to be positively related to positive symptoms in FE SZ, while no relationship was found between negative symptoms and DD. In addition, we found comparable DD in BP compared to HC. Ultimately, our data may help elucidate the psychopathology in SZ and BP during intertemporal decision making.

Greater delay discounting and cannabis coping motives are associated with more frequent cannabis use in a large sample of adult cannabis users

BACKGROUND

Self-regulation deficits expressed through a decreased ability to value future rewards (delay discounting (DD)) and impaired emotion regulation (negative urgency (NU), cannabis coping motives (CCM), and anxiety sensitivity (AS)) relate to more frequent or problematic cannabis use. However, there is a need to better understand how self-regulation and emotion regulation constructs reflect competition between deliberative and reactive systems that drive individual differences in cannabis use patterns. Further, few studies assess frequency of cannabis use within and across days of use, which may obscure differentiation of individual differences.

METHODS

In a large national sample of 2545 cannabis users, Latent Class Analysis was used to derive participant sub-classes based on two frequency indices, self-reported cannabis use days and times cannabis was used per day. Three classes emerged: Low (1-9 days/month, 1 time/day; 23 %), moderate (10-29 days/month, 2-3 times/day; 41 %), and high (30 days/month, ≥4 times/day; 36 %). Relationships among frequency classes and emotional regulation and impulsivity were assessed with a multinomial logistic regression.

RESULTS

Higher frequency use was associated with greater DD (χ2 = 6.0, p = .05), greater CCM (χ2 = 73.3, p < .001), and lower cognitive AS (χ2 = 12.1, p = .002), when controlling for demographics, tobacco use, and number of cannabis administration methods. Frequency class and NU were not significantly associated.

CONCLUSIONS

Identifying meaningful patterns of cannabis use may improve our understanding of individual differences that increase risk of frequent or problematic cannabis use. Excessive delay discounting and using cannabis to cope with negative affect may be relevant targets for treatments designed to reduce cannabis use.

Disinhibition in Frontotemporal Dementia and Alzheimer's Disease: A Neuropsychological and Behavioural Investigation

OBJECTIVE

Cognitive tests of inhibitory control show variable results for the differential diagnosis between behavioural variant of Frontotemporal Dementia (bvFTD) and Alzheimer's disease (AD). We compared the diagnostic accuracies of tests of inhibitory control and of a behavioural questionnaire, to distinguish bvFTD from AD.

METHODS

Three groups of participants were enrolled: 27 bvFTD patients, 25 AD patients, and 24 healthy controls. Groups were matched for gender, education, and socio-economic level. Participants underwent a comprehensive neuropsychological assessment of inhibitory control, including Hayling Test, Stroop, the Five Digits Test (FDT) and the Delay Discounting Task (DDT). Caregivers completed the Barratt Impulsiveness Scale 11th version (BIS-11).

RESULTS

bvFTD and AD groups showed no difference in the tasks of inhibitory control, while the caregiver questionnaire revealed that bvFTD patients were significantly more impulsive (BIS-11: bvFTD 76.1+9.5, AD 62.9+13, p < .001).

CONCLUSIONS

Neuropsychological tests of inhibitory control failed to distinguish bvFTD from AD. On the contrary, impulsivity caregiver-completed questionnaire provided good distinction between bvFTD and AD. These results highlight the current limits of cognitive measures of inhibitory control for the differential diagnosis between bvFTD and AD, whereas questionnaire information appears more reliable and in line with clinical diagnostics.

Modeling Treatment-Related Decision-Making Using Applied Behavioral Economics: Caregiver Perspectives in Temporally-Extended Behavioral Treatments

Evidence-based behavioral therapies for children with disruptive and challenging behavior rarely yield immediate improvements in behavior. For caregivers participating in behavioral therapies, the benefits from these efforts are seldom visible until after substantial time commitments. Delays associated with relief from challenging behavior (i.e., improved behavior) can influence how caregivers decide to respond to instances of problem behavior, and in turn, their continued commitment (i.e., integrity, adherence) to treatments that require long-term implementation to produce improvements in child behavior. This study applied delay discounting methods to evaluate how delays affected caregiver preferences related to options for managing their child's behavior. Specifically, methods were designed to evaluate the degree to which caregiver preferences for a more efficacious, recommended approach was affected by delays (i.e., numbers of weeks in treatment). That is, methods evaluated at which point caregivers opted to disregard the optimal, delayed strategy and instead elected to pursue suboptimal, immediate strategies. Results indicated that caregivers regularly discounted the value of the more efficacious treatment, electing to pursue suboptimal approaches when delays associated with the optimal approach grew larger. Caregivers demonstrated similar patterns of suboptimal choice across both clinical (i.e., intervention) and non-clinical (i.e., monetary) types of decisions. These findings are consistent with research that has highlighted temporal preferences as an individual factor that may be relevant to caregiver adherence to long-term evidence-based treatments and encourage the incorporation of behavioral economic methods to better understand caregiver decision-making.

Guanfacine treatment improves ADHD phenotypes of impulsivity and hyperactivity in a neurofibromatosis type 1 mouse model

Background

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder with a mutation in one copy of the neurofibromin gene (NF1^+/−). Even though approximately 40–60% of children with NF1 meet the criteria for attention deficit hyperactivity disorder (ADHD), very few preclinical studies, if any, have investigated alterations in impulsivity and risk-taking behavior. Mice with deletion of a single NF1 gene (Nf1^+/−) recapitulate many of the phenotypes of NF1 patients.

Methods

We compared wild-type (WT) and Nf1^+/− mouse strains to investigate differences in impulsivity and hyperactivity using the delay discounting task (DDT), cliff avoidance reaction (CAR) test, and open field. We also investigated whether treatment with the clinically effective alpha-2A adrenergic receptor agonist, guanfacine (0.3 mg/kg, i.p.), would reverse deficits observed in behavioral inhibition.

Results

Nf1^+/− mice chose a higher percentage of smaller rewards when both 10- and 20-s delays were administered compared to WT mice, suggesting Nf1^+/− mice are more impulsive. When treated with guanfacine (0.3 mg/kg, i.p.), Nf1^+/− mice exhibited decreased impulsive choice by waiting for the larger, delayed reward. Nf1^+/− mice also exhibited deficits in behavioral inhibition compared to WT mice in the CAR test by repetitively entering the outer edge of the platform where they risk falling. Treatment with guanfacine ameliorated these deficits. In addition, Nf1^+/− mice exhibited hyperactivity as increased distance was traveled compared to WT controls in the open field. This hyperactivity in Nf1^+/− mice was reduced with guanfacine pre-treatment.

Conclusions

Overall, our study confirms that Nf1^+/− mice exhibit deficits in behavioral inhibition in multiple contexts, a key feature of ADHD, and can be used as a model system to identify alterations in neural circuitry associated with symptoms of ADHD in children with NF1.

Intrinsic prefrontal organization underlies associations between achievement motivation and delay discounting

Achievement motivation is a core component of human decision making. However, neural mechanisms that link achievement motivation and intertemporal choice have not yet been elucidated. Here, we examined neural pathways underlying the relationship between achievement motivation and intertemporal choice using a delay discounting task and resting-state functional magnetic resonance imaging on 86 healthy subjects. Behaviorally, delay discounting rate was positively correlated with achievement motivation. Functional coupling of the dorsolateral prefrontal cortex (dlPFC) with the medial prefrontal cortex (mPFC), medial orbitofrontal cortex and ventral striatum was positively correlated with achievement motivation. Notably, the mediation analysis showed that the impact of achievement motivation on delay discounting was mediated by intrinsic connectivity between the dlPFC and mPFC. Our findings suggest that intrinsic organization within the prefrontal cortex plays a key role in linking achievement motivation and intertemporal choice.

The Role of Impulsivity Facets on the Incidence and Development of Alcohol Use Disorders

Alcohol Use Disorder (AUD) is a chronic relapsing disorder defined according to the Diagnostic and Statistical Manual of Mental Disorders 5 (DSM-5; American Psychiatric Association 2013), "by a cluster of behavioural and physical symptoms, which can include, withdrawal, tolerance and craving". Social, emotional, behavioural and cognitive factors are important contributors to AUD. Impulsivity, a multifaceted behavioural concept, defined as a predisposition for rapid and unplanned actions, without considering potential negative consequences of these actions, represents an important such factor. In this chapter, research on the role of distinct impulsivity dimensions in different severity stages of alcohol use is presented.Increased self-reported (trait) impulsivity and an inability to wait, as well as difficulty to adjust behaviour appropriately following a failure to withhold a response are observed across the spectrum of alcohol-use severities. Research on temporal impulsivity (inability to delay gratification) consistently shows deficits in more severe alcohol users. Data on temporal impulsivity in early stages of alcohol use are less consistent, with some studies showing no differences between high and moderate drinkers, while others indicating increased impulsivity in high alcohol users. Data on reflexion impulsivity are currently limited to draw conclusions. Recent research is also presented suggesting the importance of perception and interpretation of physiological and emotional signals on alcohol use behaviour highlighting the necessity of comprehensive integration of the field of the study of emotion and interoception with impulsivity research.

Neural correlates of reward magnitude and delay during a probabilistic delay discounting task in alcohol use disorder

RATIONALE

Alcohol-use disorder (AUD) is associated with the propensity to choose smaller sooner options on the delay discounting task. It is unclear, however, how inherent risk underlies delay discounting behavior. As impulsive choice is a hallmark feature in AUD, it is important to understand the neural response to reward and delay while accounting for risk in impulsive decision-making.

OBJECTIVE

This study examined activation associated with delay and reward magnitude, while controlling for risk in a probabilistic delay discounting task in AUD and examined if differences in activation were associated with treatment outcomes.

METHODS

Thirty-nine recently abstinent alcohol-dependent volunteers and 46 controls completed a probabilistic delay discounting task paired with functional magnetic resonance imaging. Alcohol use was collected using a self-report journal for 3 months following baseline scan.

RESULTS

During delay stimulus presentations, Controls exhibited greater activation compared to the Alcohol group notably in the anterior insula, middle/dorsal anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (PFC), and inferior parietal lobule. For magnitude, the Alcohol group exhibited greater activation than Controls primarily in medial PFC, rostral ACC, left posterior parietal cortex, and right precuneus. Within the Alcohol group, alcohol craving severity negatively correlated with right lateral PFC activation during reward magnitude in individuals who completed the 3-month study without relapse, while non-completers showed the opposite relationship.

CONCLUSIONS

The results of this study extend previous findings that alcohol use disorder is associated with differences in activation during an immediate or delayed choice by delineating activation associated with the parameters of impulsive choice.

Effects of Substance Misuse and Family History of Substance Use Disorder on Delay Discounting in Adolescents and Young Adults with Attention-Deficit/Hyperactivity Disorder

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) and substance use disorder (SUD) often co-occur. Both disorders are characterized by impulsive choice. However, little is known about the effects of substance misuse (SM) and family history of SUD (FH) on impulsive choice in ADHD-SUD comorbidity. Impulsive choice is also linked to callous-unemotional (CU) traits, which are suggested to play a role in ADHD-SUD comorbidity. Our aim was to examine the effects of (1) FH and (2) SM on impulsive choice, while exploring the role of CU traits.

METHODS

Impulsive choice was assessed with the delay discounting (DD) task. We compared task performance across (1) ADHD patients and controls with or without FH of SUD (ADHD FH+: n = 86; ADHD FH-: n = 63; control FH+: n = 49; control FH-: n = 72; mean age of the whole sample [n = 270]: 16.39, SD: 3.43) and (2) family history-matched ADHD groups with and without SM and controls (ADHD + SM: n = 62; ADHD-only: n = 62; controls: n = 62; mean age of the whole sample [n = 186]: 18.01, SD: 2.71). Effects of CU traits were explored by adding this as a covariate in all analyses.

RESULTS

(1) There was no main effect of FH on DD. (2) We found increased DD in ADHD + SM compared to ADHD-only and no difference between ADHD-only and controls. Finally, increased DD was associated with increased callous traits only in ADHD FH+ and control FH+.

CONCLUSIONS

In adolescents and young adults with ADHD, high impulsive choice might only be present in those with comorbid SM and in an FH+ subgroup with high callous traits. This suggests that impulsive choice in ADHD might result from (1) effects of SM and (2) a combined effect of SUD vulnerability and high callousness. Future studies should investigate efficacy of early interventions, targeting CU traits.

Single- and cross-commodity delay discounting of money and e-cigarette liquid in experienced e-cigarette users

BACKGROUND

Delay discounting (DD) research has improved our understanding of important behavioral processes associated with tobacco use. Little research has explored DD among e-cigarette users, and these studies have exclusively examined money as the only available commodity. This secondary analysis of a laboratory study explored discounting for money and e-liquid among e-cigarette users using two single-commodity discounting (SCD) tasks and one cross-commodity discounting (CCD) task. A secondary goal was to explore the extent to which results from the SCD and CCD tasks were correlated to each other and with measures of e-cigarette use.

METHODS

E-cigarette users (N = 27) completed two SCD tasks and one CCD task. The SCD tasks assessed choices between various amounts of either money now versus money later (M-M) or e-liquid now versus e-liquid later (mL-mL). The CCD task assessed choices between e-liquid now versus money later (mL-M). Discounting results were compared using logk and AUClog.

RESULTS

Discounting was greatest in the mL-mL task, followed by the M-M task, and then the mL-M task. AUClog and logk were significantly correlated across all discounting tasks. Attempts to quit vaping was positively associated with logk and negatively associated with AUClog and in both SCD tasks.

CONCLUSIONS

E-cigarette users discount e-liquid more than money in a SCD task. However, when the two commodities, money and e-liquid (CCD), are compared the substance of abuse is discounted to a lesser extent. Interventions that provide alternative reinforcers to compete with the reinforcing effects of nicotine intake may be especially indicated for treating e-cigarette dependence.

Human Brain Imaging Links Dopaminergic Systems to Impulsivity

Molecular and functional imaging techniques have been used and combined with pharmacological probes to evaluate the role of dopamine in impulsivity. Overall, strong evidence links striatal dopaminergic function with impulsivity, measured by self-reports and laboratory tests of cognitive control and reward-based decision-making. The combination of molecular imaging using positron emission tomography (PET) with functional magnetic resonance imaging (fMRI) specifically implicates striatal D2-type dopamine receptors (i.e., D2 and D3) and corticostriatal connectivity in cognitive control. Low levels of striatal and midbrain D2-type receptor availability correlate with self-reported impulsivity, whereas striatal D2-type receptor availability shows positive correlation with motor response inhibition and cognitive flexibility. Impulsive choice on reward-based decision-making tasks also is related to deficits in striatal D2-type dopamine receptor availability, and there is evidence for an inverted U-shaped function in this relationship, reflecting an optimum of striatal dopaminergic activity. Findings from studies of clinical populations that present striatal dopamine D2-type receptor deficits as well as healthy control research participants identify D2-type receptors as therapeutic targets to improve cognitive control.

Reinforcer Pathology: Implications for Substance Abuse Intervention

The rate at which individuals discount future rewards (i.e., discounting rate) is strongly associated with their propensity for substance abuse as well as myriad other negative health behaviors. An excessive preference for immediately available rewards suggests a shortened time horizon in which immediate rewards are overvalued and future, potentially negative consequences are undervalued. This review outlines Reinforcer Pathology Theory (i.e., the interaction between excessive preference for immediately available rewards and the overvaluation of a particular commodity that offers brief, intense reinforcement), its neurobiological/behavioral underpinnings, and its implications for treating substance use disorders. In doing so, the current review provides an overview of a variety of ways in which interventions have been used to manipulate aspects of reinforcer pathology in an individual, including narrative theory, framing manipulations, and neuromodulation (e.g., working memory training, TMS) which may serve as promising avenues for the modulation of the temporal window and/or valuation of reinforcers.

The relationships between eating disorder pathology and relative reinforcing value of food, delay discounting, and related constructs in adolescents

Food is a primary reinforcer that motivates behavior in the absence of learning or conditioning. Both the relative reinforcing value (RRV) of food and delay discounting are associated with weight status. While dietary restraint and disinhibition have been shown to influence the RRV of food, limited work has examined the relationships between eating disorder pathology and RRV of food and delay discounting. Therefore, the purpose of this study was to examine how eating disorder pathology predicts RRV of food, proportion of food consumed, delay discounting, reinforcement pathology (i.e., high motivation to eat and high delay discounting), and sensitization of high energy dense food (HED; i.e., increases in RRV of HED food after daily repeated exposure). Participants were 167 adolescents ages 12-14 without obesity participating in a longitudinal study examining predictors of weight change who completed a series of laboratory assessments assessing the RRV of food of HED food, delay discounting, reinforcement pathology, sensitization of HED food, and a questionnaire assessing eating disorder pathology. Eating disorder pathology was not related to the RRV of food or delay discounting, but did predict reinforcement pathology and the sensitization of HED food. When explored by weight status, these relationships were only observed for those with overweight. There were no other significant relationships for either adolescents with normal weight or overweight. Given that weight status appeared to moderate some of the relationships between eating disorder pathology and reinforcement-related constructs, future work should examine how reinforcement pathology and eating disorder pathology are related to changes in weight status over time.

Behavioral trainings and manipulations to reduce delay discounting: A systematic review

In everyday decision-making, individuals make trade-offs between short-term and long-term benefits or costs. Depending on many factors, individuals may choose to wait for larger delayed reward, yet in other situations they may prefer the smaller, immediate reward. In addition to within-subject variation in the short-term versus long-term reward trade-off, there are also interindividual differences in delay discounting (DD), which have been shown to be quite stable. The extent to which individuals discount the value of delayed rewards turns out to be associated with important health and disorder-related outcomes: the more discounting, the more unhealthy or problematic choices. This has led to the hypothesis that DD can be conceptualized as trans-disease process. The current systematic review presents an overview of behavioral trainings and manipulations that have been developed to reduce DD in human participants aged 12 years or older. Manipulation studies mostly contain one session and measure DD directly after the manipulation. Training studies add a multiple session training component that is not per se related to DD, in between two DD task measurements. Ninety-eight studies (151 experiments) were identified that tested behavioral trainings and manipulations to decrease DD. Overall, results indicated that DD can be decreased, showing that DD is profoundly context dependent and changeable. Most promising avenues to pursue in future research seem to be acceptance-based/mindfulness-based trainings, and even more so manipulations involving a future orientation. Limitations and recommendations are discussed to identify the mechanistic processes that allow for changes in discount rate and behavior accordingly.

Association between impulsivity and neural activation to alcohol cues in heavy drinkers

This study examines associations between two measures of impulsivity and brain response to alcohol taste cues. Impulsivity is both a risk factor for and a consequence of alcohol use and misuse. Frontostriatal circuits are linked to both impulsivity and addiction-related behaviors, including response to alcohol cues. Non-treatment-seeking heavy drinkers (n = 55) completed (i) an fMRI alcohol taste cue-reactivity paradigm; (ii) the monetary choice questionnaire (MCQ), a measure of choice impulsivity where participants choose between smaller, sooner rewards and larger, delayed rewards; (iii) and the UPPS-P Impulsive Behavior Scale, a self-report measure assessing five impulsivity factors. General linear models identified associations between neural alcohol taste cue-reactivity and impulsivity, adjusting for age, gender, and smoking status. Self-reported sensation seeking was positively associated with alcohol taste cue-elicited activation in frontostriatal regions, such that individuals who reported higher sensation seeking displayed greater neural response to alcohol taste cues. Conversely, delay discounting was negatively associated with activation in frontoparietal regions, such that individuals who reported greater discounting showed less cue-elicited activation. There were no significant associations between other self-reported impulsivity subscales and alcohol taste cue-reactivity. These results indicate that sensation seeking is associated with reward responsivity, while delay discounting is associated with recruitment of self-control circuitry.

Vagal signaling and the somatic marker hypothesis: The effect of transcutaneous vagal nerve stimulation on delay discounting is modulated by positive mood

Controlling impulsivity and delaying gratifications are key features of effective self-control. Delay Discounting (DD) indexes the ability to delay rewards and previous research has shown that discounting is influenced by affective states such as mood. According to the Somatic Marker Hypothesis (SMH), afferent somatic signals, such as mood, are carried by the vagus and can influence decision making. In the current study, we employed transcutaneous vagus nerve stimulation (tVNS), a novel non-invasive brain stimulation technique that stimulates the auricular branch of the afferent vagus nerve (located in the outer ear), to assess its effects on decision impulsivity, while taking into account individuals' mood and resting-state HRV as a possible confounding factor. Employing a within-subjects cross-over design, 94 participants received active or sham tVNS while performing delay discounting in two separate sessions. As compared to sham, active tVNS increased discounting, but only for individuals reporting lower positive mood, regardless of the level of negative mood reported. We evidence that the effect of tVNS on reward discounting depends on the level of positive mood. This result suggests that positive mood state might be a proxy of task-relevant arousal, likely influencing the effectiveness of afferent vagal stimulation on self-control processes, as temporal discounting.

Practicing prospection promotes patience: Repeated episodic future thinking cumulatively reduces delay discounting

BACKGROUND

Delay discounting, or the preference for smaller, sooner over larger, later rewards, has been associated with alcohol use disorder and problem drinking. Episodic future thinking has been suggested as an intervention to address steep delay discounting. In the present study, we examined the effect of up to six consecutive sessions of episodic future thinking.

METHODS

Repeated, within-subject data were collected from current and recent problem drinkers (n = 50) over six sessions. Linear mixed-effect models were used to estimate effects of repeated sessions and manipulations. Participants completed episodic future thinking interviews at up to six sessions, in which they generated personalized future events. Participants also engaged with cues of scarcity. At each session, participants completed three delay discounting tasks under: a no-cue baseline condition, a future cue condition, and a scarcity cue condition.

RESULTS

Delay discounting in the no cue condition did not change over time. Discounting rates were reduced in the future cue condition, and these effects grew larger with repeated sessions. In the scarcity condition, discounting rates were slightly higher, with no effect of repeated sessions.

CONCLUSIONS

Episodic future thinking reduced delay discounting rate while future cues were presented, and these effects grew larger with repeated sessions. This suggests that repeated episodic future thinking may cumulatively potentiate repair of excessive preference for immediate reward.

Amount and delay insensitivity during intertemporal choice in three neurodegenerative diseases reflects dorsomedial prefrontal atrophy

Patients with Alzheimer's disease and other dementias often make poor financial decisions, but it remains unclear whether this reflects specific failures in decision-making or more general deficits in episodic and working memory. We investigated how patients with Alzheimer's disease, behavioral variant frontotemporal dementia (bvFTD), and semantic variant primary progressive aphasia (svPPA) apply information in an intertemporal choice task between smaller intermediate and larger delayed rewards, with minimal memory demands. Multilevel modeling estimated subject-level sensitivities to three attributes of choice (the relative difference in reward magnitude, delay length, and absolute reward magnitudes) as well as baseline impulsivity. While baseline impulsivity in patients with Alzheimer's disease did not differ from controls, patients with bvFTD and svPPA were more impulsive than controls overall. Patients with Alzheimer's disease or bvFTD were less sensitive than controls to all three choice attributes, whereas patients with svPPA were less sensitive than controls to two attributes. Attenuated sensitivity to information presented during the choice was associated across all subjects with dorsomedial prefrontal atrophy for all three choice attributes. Given the minimal memory demands of our task, these findings suggest specific mechanisms underlying decision-making failures beyond episodic and working memory deficits in dementia.

Hunger increases delay discounting of food and non-food rewards

How do our valuation systems change to homeostatically correct undesirable psychological or physiological states, such as those caused by hunger? There is evidence that hunger increases discounting for food rewards, biasing choices towards smaller but sooner food reward over larger but later reward. However, it is not understood how hunger modulates delay discounting for non-food items. We outline and quantitatively evaluate six possible models of how our valuation systems modulate discounting of various commodities in the face of the undesirable state of being hungry. With a repeated-measures design, an experimental hunger manipulation, and quantitative modeling, we find strong evidence that hunger causes large increases in delay discounting for food, with an approximately 25% spillover effect to non-food commodities. The results provide evidence that in the face of hunger, our valuation systems increase discounting for commodities, which cannot achieve a desired state change as well as for those commodities that can. Given that strong delay discounting can cause negative outcomes in many non-food (consumer, investment, medical, or inter-personal) domains, the present findings suggest caution may be necessary when making decisions involving non-food outcomes while hungry.

Delay Discounting of Protected Sex: Relationship Type and Sexual Orientation Influence Sexual Risk Behavior

Sexual discounting, which describes delay discounting of later protected sex vs. immediate unprotected sex (e.g., sex now without a condom vs. waiting an hour to have sex with a condom), is consistently linked to sexual risk behavior. Estimates suggest that over two-thirds of HIV transmissions occur between individuals in committed relationships, but current sexual discounting tasks examine sexual discounting only with hypothetical strangers, leaving a gap in our understanding of sexual discounting with committed sexual partners. We used the Sexual Discounting Task (SDT) to compare discounting rates between men who have sex with men (MSM; n = 99) and heterosexual men (n = 144) and tested a new SDT condition evaluating sexual discounting with main partners. MSM in committed relationships discounted protected sex with their main partner at higher rates than heterosexual men, and discounting rates correlated with self-report measures of condom use, impulsivity/sensation seeking, and substance use. These findings suggest that sexual discounting is a critical factor potentially related to increased HIV transmission between MSM in committed relationships and may be an important target for intervention and prevention.

Effects of d-amphetamine and MK-801 on impulsive choice: Modulation by schedule of reinforcement and delay length

Procedural modifications can modulate drug effects in delay discounting, such as signaling the delay to reinforcement and altering the order in which delays are presented. Although the schedule of reinforcement can alter the rate at which animals discount a reinforcer, research has not determined if animals trained on different schedules of reinforcement are differentially affected by pharmacological manipulations. Similarly, research has not determined if using different delays to reinforcement can modulate drug effects in delay discounting. Male Sprague Dawley rats (n = 36) were split into four groups and were trained in a delay-discounting procedure. The schedule of reinforcement (fixed ratio [FR] 1 vs. FR 10) and delays to reinforcement (0, 5, 10, 20, and 50 s vs. 0, 10, 30, 60, 100 s) were manipulated for each group. Following behavioral training, rats were treated with d-amphetamine (0, 0.25, 0.5, and 1.0 mg/kg) and MK-801 (0, 0.03, and 0.06 mg/kg). Results showed that amphetamine decreased impulsive choice when a FR 1 schedule was used, but only when the short delay sequence was used. Conversely, amphetamine decreased impulsive choice when a FR 10 schedule was used, but only when rats were trained on the long delay sequence. MK-801 decreased impulsive choice in rats trained on a FR 1 schedule, regardless of delay sequence, but did not alter choice in rats trained on a FR 10 schedule. These results show that schedule of reinforcement and delay length can modulate drug effects in delay discounting.

An Information Theoretic Approach to Model Selection: A Tutorial with Monte Carlo Confirmation

A reliance on null hypothesis significance testing (NHST) and misinterpretations of its results are thought to contribute to the replication crisis while impeding the development of a cumulative science. One solution is a data-analytic approach called Information-Theoretic (I-T) Model Selection, which builds upon Maximum Likelihood estimates. In the I-T approach, the scientist examines a set of candidate models and determines for each one the probability that it is the closer to the truth than all others in the set. Although the theoretical development is subtle, the implementation of I-T analysis is straightforward. Models are sorted according to the probability that they are the best in light of the data collected. It encourages the examination of multiple models, something investigators desire and that NHST discourages. This article is structured to address two objectives. The first is to illustrate the application of I-T data analysis to data from a virtual experiment. A noisy delay-discounting data set is generated and seven quantitative models are examined. In the illustration, it is demonstrated that it is not necessary to know the "truth" is to identify the one that is closest to it and that the most likely models conform to the model that generated the data. Second, we examine claims made by advocates of the I-T approach using Monte Carlo simulations in which 10,000 different data sets are generated and analyzed. The simulations showed that 1) the probabilities associated with each model returned by the single virtual experiment approximated those that resulted from the simulations, 2) models that were deemed close to the truth produced the most precise parameter estimates, and 3) adding a single replicate sharpens the ability to identify the most probable model.

Linking Delay Discounting and Substance Use Disorders: Genotypes and Phenotypes

Research supports the idea that "delay discounting," also known as temporal discounting, intertemporal choice, or impulsive choice, is a transdisease process with a strong connection to substance use disorders (SUDs) and other psychopathologies, like attention deficit hyperactivity disorder and depression. This article briefly reviews the evidence used to conclude that delay discounting is heritable and should be considered to be an endophenotype, as well as evidence of its behavioral and genetic associations with SUDs. It also discusses the limitations that should be considered when evaluating the strength of these associations. Finally, this article briefly describes research examining relationships among delay discounting and SUD-associated intermediate phenotypes to better understand the conceptual relationships underlying the links between SUDs and delay discounting, and identifies research gaps that should be addressed.

Impulsivity in the self-harm and suicidal behavior of young people: A systematic review and meta-analysis

BACKGROUND

Impulsivity is considered a possible phenotype underlying the expression of self-harm and suicidal behaviors. Yet impulsivity is a not a unitary construct and there is evidence that different facets of impulsivity follow different neurodevelopmental trajectories and that some facets may be more strongly associated with such behaviors than others. Moreover, it is unclear whether impulsivity is a useful predictor of self-harm or suicidal behavior in young people, a population already considered to display heightened impulsive behavior.

METHODS

A systematic review and meta-analysis of studies published in Medline, PubMed, PsychInfo or Embase between 1970 and 2017 that used a neurocognitive measure to assess the independent variable of impulsivity and the dependent variable of self-harm and/or suicidal behavior among young people (mean age < 30 years old).

RESULTS

6183 titles were identified, 141 full texts were reviewed, and 18 studies were included, with 902 young people with a self-harm or suicidal behavior and 1591 controls without a history of these behaviors. Deficits in inhibitory control (13 studies, SMD 0.21, p-value = 0.002, 95% confidence interval (CI) (0.08-0.34), prediction interval (PI) = 0.06-0.35) and impulsive decision-making (14 studies, SMD 0.17, p-value = 0.008, 95% CI (0.045-0.3), PI = 0.03-0.31) were associated with self-harm or suicidal behavior. There were no significant differences between measures of different facets of impulsivity (ie. delay discounting, risky decision-making, cognitive or response inhibition) and self-harm or suicidal behavior.

CONCLUSION

Multiple facets of impulsivity are associated with suicidal behavior in young people. Future suicide research should be designed to capture impulsive states and investigate the impact on different subtypes of impulsivity.

The preference for future outcomes correlates with the temporal variability of functional connectivity among brain regions

People inevitably make decisions between short-term and long-term consequences across domains like education, health and economics. In this kind of decision, the tendency to discount the value of later-larger rewards with increasing delays is defined as delay discounting (DD). A recent review has suggested that three neural systems which respectively responsible for valuation, prospection and cognitive control (e.g., ventromedial prefrontal cortex [vmPFC], hippocampus, precuneus and dorsolateral prefrontal cortex [dlPFC]) could interact with each other flexibly to have impacts on DD. However, to date, there is little attention paid on the connection between the DD and the dynamic interaction of brain regions.To tackle this issue, we investigate the relationship between the DD and the time-varying connectivity among brain regions in two samples of young adults. Results in sample 1 found that the DD was negatively correlated with the temporal variability of functional connectivity [FC] between the vmPFC and precuneus, and between the vmPFC and the left superior frontal gyrus. And the temporal variabilities of FC between the ventral striatum and right dlPFC, and between the ventral striatum and dorsomedial prefrontal cortex were also negatively related to DD. Furthermore, the main results were well replicated and validated in another sample using different analysis parameters. Overall, our findings reveal that temporal fluctuation of FC within default mode and fronto-striatal circuits can favor for prospecting future, cognitive control and valuation of delayed incentives, and this flexible connectivity patterns generally have association with preference for future outcomes.

Intertemporal decision-making-related brain states predict adolescent drug abuse intervention responses

Adolescent drug misuse represents a major risk factor for long-term drug use disorders. However, wide individual differences in responses to first-line behavioral therapies targeting adolescent drug misuse limit critical early intervention. Identifying the neural signatures of those adolescents most likely to respond to an intervention would potentially guide personalized strategies for reducing drug misuse. Prior to a 14-week evidence-based intervention involving combinations of contingency management, motivational enhancement, and cognitive behavioral therapy, thirty adolescent alcohol and/or cannabis users underwent fMRI while performing a reward delay discounting (DD) task tapping an addiction-related cognition. Intervention responses were longitudinally characterized by both urinalysis and self-report measures of the percentage of days used during treatment and in post-treatment follow-up. Group independent component analysis (ICA) of task fMRI data identified neural processing networks related to DD task performance. Separate measures of wholesale recruitment during immediate reward choices and within-network functional connectivity among selective networks significantly predicted intervention-related changes in drug misuse frequency. Specifically, heightened pre-intervention engagement of a temporal lobe "reward motivation" network for impulsive choices on the DD task predicted poorer intervention outcomes, while modes of functional connectivity within the reward motivation network, a prospection network, and a posterior insula network demonstrated robust associations with intervention outcomes. Finally, the pre-intervention functional organization of the prospection network also predicted post-intervention drug use behaviors for up to 6 months of follow-up. Multiple functional variations in the neural processing networks supporting preference for immediate and future rewards signal individual differences in readiness to benefit from an effective behavioral therapy for reducing adolescent drug misuse. The implications for efforts to boost therapy responses are discussed.

Smoking policies in the home have less influence on cigarettes per day and nicotine dependence level among African American than White smokers: A cross-sectional analysis

BACKGROUND

African American smokers suffer disproportionately from tobacco-related disease caused, in part, by lower rates of smoking cessation. We examined whether smoke-free home policies and delay discounting were differentially associated with cigarettes smoked per day (CPD) and nicotine dependence (ND) among African Americans and Whites.

METHODS

Secondary data analysis was conducted using data from 65 African American (n = 40) and White (n = 25) smokers who completed measures of CPD, ND, tobacco craving, stress, depression, home smoking policy, and delay discounting.

RESULTS

A significant interaction was found between race and home smoking policy on CPD (B = -11.21, p = 0.002) and ND (B = -3.42, p = 0.004). Smoke-free policies in the home were associated with fewer CPD and lower ND levels among Whites, but not among African Americans. Whites who allowed smoking in their homes had significantly greater mean CPD and higher mean ND than their counterparts who did not allow smoking in the home. Among African American smokers, there were no differences in CPD and ND among those who allowed smoking in their home versus those who did not.

CONCLUSIONS

The findings extend the scientific literature by suggesting that a malleable environmental factor (home smoking policy) commonly associated with cessation among Whites does not have the same influence on cessation among African American.

Dysregulation as a correlate of cannabis use and problem use

OBJECTIVE

Cannabis users with a dysregulatory risk factor may be particularly vulnerable to engaging in more frequent and problematic cannabis use. Contemporary models of dysregulated behavior suggest that dysregulation emerges due to distinct mechanisms. The current study seeks to examine the dysregulatory correlates of cannabis involvement, including working memory capacity, delay discounting, impulsivity, and reward sensitivity.

METHOD

Participants were 104 non-treatment seeking frequent cannabis users (the average participant used cannabis 71% of the days/past 60 days [SD = 22%], with an average of two uses per day [SD = 1.2]). Mean age was 21.3 (SD = 4.3); 36.5% were female. Working memory was assessed via the Trail-Making Test-B and the Digit Span subtests of the WAIS-III, delay discounting was assessed via a computer-based task, trait impulsivity was self-reported via the Barratt Impulsiveness Scale, and reward sensitivity was self-reported via the Reward Dependence Scale and the Snaith-Hamilton Pleasure Scale.

RESULTS

Structural equation modeling estimated the associations between different facets of dysregulation and cannabis involvement. Results suggest that poor working memory capacity and high trait impulsivity were associated with both use and problem use. Greater delay discounting was associated with problem use, but not with frequency of use. Low reward sensitivity was associated with more frequent cannabis use, but not with problem use.

CONCLUSIONS

Results confirm that the dysregulatory correlates of cannabis involvement consist of multiple dimensions of functioning. Prospective studies that assess the multidimensional structure of dysregulation and cannabis involvement are needed in order to disaggregate the dysregulatory antecedents and consequences of cannabis involvement.

Using an Experimental Medicine Approach to Identify Novel Determinants of Addiction

Our understanding and effectiveness in treating addiction is not fully adequate. Therefore, perhaps developing a pragmatic theory for identifying novel determinants and potential interventions is needed. The experimental medicine approach, derived from Claude Bernard, proposes a methodology for inductive theory development and suggests interventions directed at targets closely aligned with the underlying mechanisms of the disorder. The steps of theory development under this approach are intended to (1) identify an intervention target; (2) develop assays to verify target measurement; (3) engage the target via experiment or intervention; and (4) test the degree to which target engagement produces other therapeutically useful changes in the disorder. In this article, we review these steps in detail using an example from our work. That is, shortened temporal windows (target) is frequently observed among those who are addicted. Delay discounting is an assay used to measure that target. We and others have demonstrated manipulation of the target, delay discounting, is associated with changing the drug valuation among those with addiction. We conclude with a culmination of the experimental medicine approach by proposing a recently developed hypothesis of substance use disorder, Reinforcer Pathology 2.0.

An experimental investigation of the role of delay discounting and craving in gambling chasing behavior

Chasing is a central feature of gambling disorder and refers to the attempt by individuals to recover financial losses by continuing to gamble. Although several efforts have been made to individuate the factors involved in the complex phenomenon of chasing, little is known regarding its association with delay discounting and craving, both considered important in the development and maintenance of gambling disorder. In the present study, the interplay between chasing, delay discounting, and craving (while controlling for gambling severity) was investigated. The sample comprised 128 adult gamblers aged between 18 and 67 years and consisted of non-problem gamblers (n = 58), problem gamblers (n = 18), and pathological gamblers (n = 52) based on the South Oaks Gambling Screen (SOGS) scores. Participants were administered the Monetary Choice Questionnaire (MCQ) and the Gambling Craving Scale (GACS), as well as completing the ChasIT, a computerized task assessing chasing behavior. Participants were randomly assigned to the control and the loss condition of the ChasIT. Results showed that pathological gamblers were more likely to chase and reported more severe chasing persistence. Regression analyses indicated that heightened levels of craving and the inability to tolerate delay in gratification, along with gambling severity, predicted both the decision to chase and chasing persistence. The present study contributes important findings to the gambling literature, highlighting the role of craving and delay discounting in facilitating the inability to stop within-sessions gambling. These findings may provide evidence that chasers and non-chasers represent two different types of gamblers, and that the difference may be useful for targeting more effective therapies.

Reinforcer pathology: Common neural substrates for delay discounting and snack purchasing in prediabetics

Reinforcer pathology theory stipulates that individuals with both (a) high preference for smaller, immediate over larger, delayed rewards; and (b) high demand for unhealthy commodities are uniquely susceptible to poor health outcomes. Specifically, two behavioral economic tasks (delay discounting, assessing preference for smaller, immediate or larger, delayed rewards; and purchasing, assessing purchases of commodities over changes in price) have been independently associated with conditions such as overweight/obesity and problem substance use. In the present study, we examined possible shared neural regions involved in the processes of delay discounting and demand for snack foods in a prediabetic sample. Fifty-four participants completed both of these tasks. Conjunction between delay discounting and purchasing task results indicates substantial common neural substrates recruited during these two tasks, consistent with interpretations of executive control, interoception, and attention, in the prefrontal cortex, insula, and frontoparietal cortex (superior/middle frontal cortex and superior/inferior parietal lobules), respectively. Collectively, these results suggest possible neural substrates in which the two behavioral risk factors of reinforcer pathology may interact during real-world decision-making in prediabetes.

Measuring facets of reward sensitivity, inhibition, and impulse control in individuals with problematic Internet use

INTRODUCTION

Problematic Internet Use (PIU) is the inability to control the amount of time spent on the Internet. Research indicates that abnormalities in reward sensitivity, sensitivity to punishment, and impulse control drive addictive behaviors such as substance abuse and gambling disorders, but it is unclear whether this is also the case in PIU.

METHODS

Behavioral tasks and scales were completed by 62 participants (32 PIU individuals and 30 no-PIU individuals) to assess reward sensitivity, sensitivity to punishment, as well as inhibitory function and impulse control. Measures administered included Go/No-Go, delay discounting, Behavioral Inhibition/Activation (BIS/BAS) scales and the Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSRQ).

RESULTS

The PIU group endorsed greater reward sensitivity and punishment sensitivity as indexed by the SPSRQ. However, there were no group differences with regards to delay discounting, performance in the Go/No-Go task, or endorsement in the BIS/BAS scales.

DISCUSSION

The present study found increased reward sensitivity and sensitivity to punishment in PIU individuals, though impulse control was not observably affected. Future experimental studies are needed to inform our conceptualization of the etiology of addictive behavior as it pertains to PIU. Further investigation will aid in informing prevention and intervention efforts.

Intergenerational transmission of delay discounting: The mediating role of household chaos

INTRODUCTION

Adolescence is a period when impulsive decision making may be especially vulnerable to environmental influences. Impulsive decision making is often assessed using a delay discounting paradigm, which measures the preference for smaller rewards sooner over larger rewards with a delay. Research is needed to clarify the relationship between parents' and adolescents' delay discounting and to identify related environmental processes that might facilitate the intergenerational transmission of delay discounting. The current prospective longitudinal study examined the competing mediating processes of household chaos and harsh parenting in the intergenerational transmission of delay discounting between parents and adolescents.

METHODS

Participants included 167 adolescents (mean age = 14.07 years at Time 1; 53% male) and their parents (mean age = 41.98 years at Time 1; 87% female) recruited from the southeast United States. Parents' delay discounting was collected at Time 1, and adolescents' delay discounting was collected both at Time 1 and at Time 3 via a computerized delay discounting task. Parents and adolescents reported household chaos and harsh parenting at Time 2.

RESULTS

A parallel mediation model indicated that parents' delay discounting at Time 1 indirectly predicted adolescents' delay discounting Time 3 residualized change scores (regressing Time 3 delay discounting onto baseline delay discounting) through household chaos but not through harsh parenting at Time 2.

CONCLUSIONS

These results underline the importance of household chaos in facilitating the intergenerational transmission of delay discounting between parents and adolescents. Furthermore, our findings point to household chaos as a potential environmental target for interrupting intergenerational impulsivity.

Education and mental health: Do psychosocial resources matter?

Prevalence rates for mental health problems are higher when an individual's socioeconomic status (SES) is low, but the underlying mechanisms are not clearly understood. We investigated associations between education as indicator for SES and depressive symptoms as well as positive mental health (PMH). Moreover, we hypothesized that low education is associated with a lack of psychosocial resources and more daily hassles, which in turn mediate the relationships between education and mental health. In a German representative sample (N = 7937), we cross-sectionally first examined whether a person's educational level was associated with depressive symptoms and PMH. Educational level was defined as the highest academic qualification achieved. Second, we investigated whether also sense of control, resilience, delay of gratification, cultural activity and daily hassles followed gradients along the educational level. Third, we investigated whether they mediated the relationship between education and mental health. Results showed that depressive symptoms measured by items from the DASS-42 depression subscale were more prevalent for persons with a low educational level, PMH operationalized by the Positive Mental Health Scale was equally distributed, and all psychosocial characteristics followed the gradient of educational level. In addition, the group with a high school diploma was particularly burdened. Structural equation modeling indicated that the associations between education and mental health were mediated by all psychosocial characteristics and daily hassles, apart from the delay of gratification. In the group with the lowest educational level the model fit indices for depressive symptoms and PMH were acceptable (χ2 = 10007.243 (627), CFI = 0.869, RMSEA = 0.04 (90% CI [0.04, 0.04], SRMR = 0.05; and χ2 = 12779.968 (741), CFI = 0.86, RMSEA = 0.05 (90% CI [0.05, 0.05], SRMR = 0.05), respectively). The effect size Pm refers to the proportion of the total effect that is mediated by one or more variables ("M"), and the effect size of all indirect effects in the model for depressive symptoms was Pm = .80 and for PMH it was Pm = .68. The results support our hypotheses that low education is associated with less psychosocial resources, which in turn serve together with daily hassles as pathways between education and depressive symptoms as well as PMH. Building on these findings, longitudinal studies are necessary to investigate causality.

On Four Types of Devaluation of Outcomes Due to Their Costs: Delay, Probability, Effort, and Social Discounting

Discounting refers to decreases in the subjective value of an outcome with increases in some attribute of that outcome. The attributes most commonly studied are delay and probability, with far less research on effort and social discounting. Although these attributes all represent costs that reduce subjective value, it is as yet unclear how the extent to which they do so is related at the individual level. Accordingly, the present study examined the degree to which individual participants discounted hypothetical monetary rewards on each of four discounting tasks in which the delay, probability, effort, and number of people with whom the money was to be shared were manipulated. At the group level, larger amounts were discounted less steeply than smaller amounts when delay and effort were varied, whereas larger amounts were discounted more steeply when probability and number of people were varied. At the individual level, the correlational pattern was examined using exploratory factor analysis. A six-factor structure (with separate factors for delay and effort, and two factors each for social and probability discounting) described the relations among indifference points. At a more molar level, a two-factor structure, which corresponded to the direction of the observed magnitude effects, described the relations among area-under-the-curve measures of discounting in the eight conditions resulting from crossing two monetary amounts with the four cost factors. We conclude that despite sharing some similarities, individual and group differences in discounting involving the different types of costs reflect mostly separate processes and traits.

Role of delay discounting in predicting change in HBA1c for individuals with prediabetes

The majority of people with prediabetes transition to type 2 diabetes. Weight gain is a known predictor of increasing the risk of diabetes, but another reason may be a focus on immediate rewards and discounting of the future. Delay discounting (DD: devaluation of future consequences) is related to obesity and poor glycemic control in persons with type 2 diabetes. This study was designed to assess whether changes in DD are associated with HbA1c change beyond BMI change in individuals with prediabetes. Hierarchical regression showed changes in BMI (p = 0.008) and the $1000 DD task (p = 0.04) were associated with HbA1c change beyond demographic characteristics, with the full model accounting for 25.8% of the variance. Those with greater BMI increases and greater increases in discounting of the future showed the greatest increases in HbA1c. DD represents a novel target to prevent progression from prediabetes to type 2 diabetes.

An investigation of delay and probability discounting in hoarding disorder

Behavioral impulsivity may be a mechanism of hoarding disorder (HD). A commonly used and well-validated measure of impulsivity is the delay and probability discounting task, which consists of making decisions about receiving monetary rewards after varying delay intervals and delivery probabilities. We compared delay and probability discounting and self-reported behavioral impulsivity in 81 patients with a primary diagnosis of HD and 45 nonclinical controls. HD participants completed the impulsivity measures before and after 16 weekly sessions of cognitive-behavioral therapy (CBT), whereas control group participants completed the measures before and after a 16-week waiting period. Despite the fact that self-reported impulsivity was greater in the HD group than the control group, delay and probability discounting did not differ between groups. Additionally, while self-reported behavioral impulsivity improved over the course of CBT in HD participants, delay and probability discounting did not change during treatment. Furthermore, higher delay discounting scores (i.e., greater preference for immediate rewards, indicating greater impulsivity) were associated with lower hoarding symptom severity. The findings suggest that self-reported impulsivity, but not objective performance on a behavioral impulsivity task, may be impaired in HD, and are discussed in terms of cognitive and affective factors in decision-making.

The relationship between delay discounting and alcohol dependence in individuals with and without comorbid psychopathology

RATIONALE

Alcohol use disorder (AUD) has been associated with greater discounting of delayed monetary rewards, but it is unclear whether this association is primarily related to alcohol consumption or is secondary to the presence of psychiatric comorbidities. It is also unclear if steeper rates of discounting are associated with greater AUD severity.

OBJECTIVE

We sought to determine whether the presence of comorbid psychiatric disorders affected the relationship between AUD and delay discounting. We also examined whether more severe AUD was associated with greater delay discounting.

METHODS

In this cross-sectional study, 793 adults completed a delay discounting task. Subjects were divided into four groups based on diagnosis: current AUD with psychiatric comorbidities (N = 226), current AUD without psychiatric comorbidities (N = 203), past AUD (N = 69), and healthy controls (N = 295). In those with AUD, we investigated the relationship between delay discounting and alcohol dependence symptom count and recent drinking history. We also compared individuals seeking treatment to non-treatment seeking individuals. Psychiatric comorbidities examined included mood disorders, anxiety disorders, and substance use disorders.

RESULTS

After adjusting for age, sex, income, and education, individuals with current AUD showed significantly higher rates of delay discounting than healthy controls and individuals with a past diagnosis of AUD. The presence of comorbid psychiatric diagnoses was not associated with steeper discounting. Among those with AUD, there was no evidence for a continuous relationship between delay discounting and AUD severity or alcohol consumption. Finally, non-treatment seekers with AUD had steeper delay discounting than treatment seekers.

CONCLUSIONS

Individuals with AUD show steeper delay discounting than healthy adults, but the effect is small and there is no added effect from comorbid psychopathology or increased AUD severity. This suggests that steeper delay discounting may have a more limited effect on human alcohol use than previously supposed.

Joint modeling of reaction times and choice improves parameter identifiability in reinforcement learning models

BACKGROUND

Reinforcement learning models provide excellent descriptions of learning in multiple species across a variety of tasks. Many researchers are interested in relating parameters of reinforcement learning models to neural measures, psychological variables or experimental manipulations. We demonstrate that parameter identification is difficult because a range of parameter values provide approximately equal quality fits to data. This identification problem has a large impact on power: we show that a researcher who wants to detect a medium sized correlation (r = .3) with 80% power between a variable and learning rate must collect 60% more subjects than specified by a typical power analysis in order to account for the noise introduced by model fitting.

NEW METHOD

We derive a Bayesian optimal model fitting technique that takes advantage of information contained in choices and reaction times to constrain parameter estimates.

RESULTS

We show using simulation and empirical data that this method substantially improves the ability to recover learning rates.

COMPARISON WITH EXISTING METHODS

We compare this method against the use of Bayesian priors. We show in simulations that the combined use of Bayesian priors and reaction times confers the highest parameter identifiability. However, in real data where the priors may have been misspecified, the use of Bayesian priors interferes with the ability of reaction time data to improve parameter identifiability.

CONCLUSIONS

We present a simple technique that takes advantage of readily available data to substantially improve the quality of inferences that can be drawn from parameters of reinforcement learning models.

To smoke or not to smoke: Does delay discounting affect the proximal choice to smoke?

BACKGROUND

Delay discounting rate shows robust predictive validity for tobacco use behaviors and is a new therapeutic target in the treatment of tobacco use. Identifying factors that influence relations between delay discounting and the choice to smoke cigarettes is key to the development of effective interventions that target delay discounting to reduce cigarette consumption.

OBJECTIVE

To examine relations between delay discounting, motivational factors, self-efficacy, nicotine dependence level, and the proximal choice to smoke in the context of other commonly rewarding activity choices.

METHODS

In this cross-sectional design, daily smokers (n = 480) from Amazon Mechanical Turk completed a questionnaire that assessed delay discounting rate; motivation, intention, and self-efficacy to quit smoking; nicotine dependence level, and the preference for immediately engaging in multiple commonly rewarding activities. We hypothesized that 1) greater motivation to quit would be associated with lower priority given to smoking; 2) the relation between delay discounting and the priority given to smoking would be mediated by motivation, self-efficacy, and nicotine dependence level.

RESULTS

Greater motivation to quit was significantly associated with a lower priority given to smoking. The relation between delay discounting and the priority given to smoking was marginally mediated by nicotine dependence level (p > .057).

CONCLUSIONS

Motivation to quit influences decision-making by impacting the prioritization of choices. Nicotine dependence is likely to mediate the relation between delay discounting and the choice to smoke. Interventions that target delay discounting to reduce cigarette consumption or prevent relapse need to account for motivation to quit and nicotine dependence level.

Greater tolerance to losses in sensation seeking: Evidence from probability and delay discounting

BACKGROUND

Sensation seeking is a behavioral endophenotype of substance use and is associated with abnormalities in financial reward processing. Previous research suggests that high sensation seekers (HSS) relative to low sensation seekers (LSS) show either an enhanced sensitivity to financial rewards or a reduced sensitivity to financial punishments. However, there are few studies investigating the valuation of financial rewards and punishments as a function of delivery probability and delay, two important aspects of reward processing that influence the valuation.

METHODS

We administrated a probability discounting task and a delay discounting task to 56 HSS and 57 LSS selected from a large sample. Each task was crossed with two factors: valence (gain vs. loss) and amount (Ұ1000 vs. Ұ50000).

RESULTS

For the probability discounting task, HSS discounted probabilistic losses but not gains more steeply than LSS, irrespective of the amount of outcome. For the delay discounting task, HSS discounted delayed losses more steeply than LSS, for the large but not small amount condition. In contrast, both groups exhibited comparable discounting rates for gains across the two amount conditions. These results remained significant when impulsivity levels were controlled for.

CONCLUSIONS

Together, our data strengthen the argument that the dysfunctional valuation in sensation seeking is valence specific, which may be driven by a weaker avoidance system, rather than by a stronger approach system.

ADHD-related sex differences in fronto-subcortical intrinsic functional connectivity and associations with delay discounting

Background

Attention-deficit/hyperactivity disorder (ADHD) is associated with atypical fronto-subcortical neural circuitry and heightened delay discounting, or a stronger preference for smaller, immediate rewards over larger, delayed rewards. Recent evidence of ADHD-related sex differences in brain structure and function suggests anomalies in fronto-subcortical circuitry may differ among girls and boys with ADHD. The current study examined whether the functional connectivity (FC) within fronto-subcortical neural circuitry differs among girls and boys with ADHD compared to same-sex typically developing (TD) controls and relates to delay discounting.

Methods

Participants include 8–12-year-old children with ADHD (n = 72, 20 girls) and TD controls (n = 75, 21 girls). Fronto-subcortical regions of interest were functionally defined by applying independent component analysis to resting-state fMRI data. Intrinsic FC between subcortical components, including the striatum and amygdala, and prefrontal components, including ventromedial prefrontal cortex (vmPFC), anterior cingulate cortex (ACC), and anterior dorsolateral prefrontal cortex (dlPFC), was compared across diagnostic groups overall and within sex. Correlations between intrinsic FC of the six fronto-subcortical pairs and delay discounting were also examined.

Results

Both girls and boys with ADHD show atypical FC between vmPFC and subcortical regions including the striatum (stronger positive FC in ADHD) and amygdala (weaker negative FC in ADHD), with the greatest diagnostic effects among girls. In addition, girls with ADHD show atypical intrinsic FC between the striatum and dlPFC components, including stronger positive FC with ACC and stronger negative FC with dlPFC. Further, girls but not boys, with ADHD, show heightened real-time delay discounting. Brain–behavior correlations suggest (1) stronger negative FC between the striatal and dlPFC components correlated with greater money delay discounting across all participants and (2) stronger FC between the amygdala with both the dlPFC and ACC components was differentially related to heightened real-time discounting among girls and boys with and without ADHD.

Conclusions

Our findings suggest fronto-subcortical functional networks are affected in children with ADHD, particularly girls, and relate to delay discounting. These results also provide preliminary evidence of greater disruptions in fronto-subcortical FC among girls with ADHD that is not due to elevated inattention symptom severity, intellectual reasoning ability, age, or head motion.

Electronic supplementary material

The online version of this article (10.1186/s11689-018-9254-9) contains supplementary material, which is available to authorized users.

Functional MRI and delay discounting in patients infected with hepatitis C

Hepatitis C virus-infected (HCV+) adults evidence increased rates of psychiatric and cognitive difficulties. This is the first study to use functional magnetic resonance imaging (fMRI) to examine brain activation in untreated HCV+ adults. To determine whether, relative to non-infected controls (CTLs), HCV+ adults exhibit differences in brain activation during a delay discounting task (DDT), a measure of one's tendency to choose smaller immediate rewards over larger delayed rewards-one aspect of impulsivity. Twenty adults with HCV and 26 CTLs completed an fMRI protocol during the DDT. Mixed effects regression analyses of hard versus easy trials of the DDT showed that, compared with CTLs, the HCV+ group exhibited less activation in the left lateral occipital gyrus, precuneus, and superior frontal gyrus. There were also significant interactive effects for hard-easy contrasts in the bilateral medial frontal gyrus, left insula, left precuneus, left inferior parietal lobule, and right temporal occipital gyrus; the CTL group evidenced a positive relationship between impulsivity and activation, while the HCV+ group exhibited a negative relationship. Within the HCV+ group, those with high viral load chose immediate rewards more often than those with low viral load, regardless of choice difficulty; those with low viral load chose immediate rewards more often on hard choices relative to easy choices. Results show that HCV+ patients exhibit greater impulsive behavior when presented with difficult choices, and impulsivity is negatively related to activation in regions important for cognitive control. Thus, interventions that decrease impulsive choice may be warranted with some HCV+ patients.

Interventions aimed at changing impulsive choice in rats: Effects of immediate and relatively long delay to reward training

A relatively strong preference for smaller-sooner rewards (SSR) over larger-later rewards (LLR) is associated with a host of maladaptive behavioral patterns. As such, the clinical implications for increasing preference for LLR are profound. There is a growing body of literature that suggests extended exposure to delayed reward may increase preference for LLR in rats. However, questions remain about the underlying mechanism driving this effect and the extent to which extended exposure to immediate rewards may decrease LLR choice. In Experiment 1, we tested effects of a differential-reinforcement-of-low-rates schedule (DRL) to increase LLR choice using a pretest/posttest design with Wistar rats as subjects. We compared this group to a group of rats exposed to a differential-reinforcement-of-high-rates schedule (DRH). The DRH intervention has never been employed in this research context, but explicitly programs an immediate response-reinforcement requirement. In Experiment 2, we tested effects of an intervention with a delay longer than those used in the delay discounting pretest and posttest. No previous research has tested effects of an intervention delay this long, relative to the delay discounting task. We compared this group to a group exposed to a delay that was part of the delay discounting pretest and posttest and to a group exposed to a traditional no-delay, fixed-ratio (FR) 2 control intervention. In both experiments, we found that exposure to delayed rewards in the intervention phase significantly increased LLR choice relative to pretest performance. These findings replicate and extend a growing body of literature showing that delay exposure increases preference for LLR. We also found significant decreases in LLR choice from pretest to posttest in the DRH and no-delay intervention groups in Experiments 1 and 2, respectively. This is the first report of such an effect and has implications for understanding and interpreting effects of delay exposure training in past and future research. Our results also suggested no relationship between improved temporal tracking of reward and increases in LLR choice as a result of delay exposure training.

Peer influence, Frontostriatal connectivity, and delay discounting in African American emerging adults

Prior research has demonstrated the importance of delay discounting in adverse health behaviors, such as addiction, attention deficit hyperactivity disorder, risk taking, and obesity. Nevertheless, the functional connectivity of neural circuitry associated with delay discounting and the ways in which the social environment may influence frontostriatal connectivity remain largely unknown, particularly in African Americans. Building on recent literature implicating frontostriatal connectivity during active delay discounting decision making and at rest, we used functional magnetic resonance imaging to assess the association between delay discounting and frontostriatal resting state connectivity (rsFC). We also examined the capacity of social relationships with parents and peers to longitudinally predict frontostriatal rsFC. The study cohort was composed of 91 rural African American emerging adults followed over a 6-year period. Greater (i.e., more positive) frontostriatal rsFC was associated with decreased delay discounting (i.e., less impulsive decision making). In addition, peer relationships at ages 20 and 21 significantly predicted frontostriatal rsFC at age 25 above and beyond parental influence. A significant indirect effect of peer affiliation on delay discounting through frontostriatal rsFC also emerged. These results indicate a role of frontostriatal connectivity in delay discounting decision making and highlight peers' unique influence on decision making behaviors through frontostriatal rsFC during emerging adulthood.

Delay discounting and e-cigarette use: An investigation in current, former, and never cigarette smokers

BACKGROUND

Cigarette smokers show greater delay discounting (devaluation of delayed consequences) than non-smokers, suggesting that rapid devaluation of the future contributes to tobacco use through a mechanism in which tobacco-related health consequences are too delayed to discourage smoking. However, little work has quantified delay discounting in relation to electronic cigarette (EC) use, a tobacco product that many users believe to pose fewer negative health consequences than cigarettes.

METHODS

We assessed discounting of delayed monetary rewards in a web-based sample of 976 participants, stratified by both EC use (current and never) and cigarette use (current, former, and never).

RESULTS

Controlling for demographic variance, current EC users generally showed greater discounting than never EC users (p = .019). Current cigarette smokers also showed greater discounting than former and never smokers (p < .001). However, the between-group difference for EC use was much smaller (η_p² = .006) than for cigarette use (η_p² = .026). Moreover, differences in discounting in relation to EC use were not statistically apparent in most pairwise comparisons. Most notably, the difference between former smokers who achieved smoking cessation by transitioning to ECs (i.e., exclusive EC users) and those who have never used ECs or cigarettes was nonsignificant and small (η_p² = .010).

CONCLUSIONS

The smaller effect size for the association between delay discounting and current EC use, relative to current cigarette use, suggests that public perception of ECs as a safer alternative to cigarettes attenuates the role of delay discounting in decisions to use ECs.

Trajectories of impulsivity by sex predict substance use and heavy drinking

Although impulsivity and sensation seeking have been consistently associated with substance use, few studies have analyzed the relationship between changes in these variables and substance use in early adolescents. The aim of this study was to identify trajectories of impulsivity and sensation seeking and explore their relationship with substance use and heavy drinking. A total of 1342 non-user adolescents (53.6% males; mean age = 12.98, SD = 0.50) annually completed the Barratt Impulsiveness Scale, the Zuckerman's Impulsive Sensation Seeking scale and a delay discounting task, over a total period of three years. Past alcohol, tobacco and cannabis use, drunkenness episodes (DE) and problem drinking were also assessed. Impulsivity trajectories were explored using latent class mixed modelling. To study their predictive power binary logistic regressions were used. Two trajectories of impulsivity were found in males and five were found in females. Males with an increasing impulsivity trajectory were more likely to report tobacco [odds ratio (OR) = 1.84] and cannabis (OR = 3.01) use, DE (OR = 2.44) and problem drinking (OR = 3.12). The early increasing trajectory in females predicted tobacco use (OR = 3.71), cannabis use (OR = 5.87) and DE (OR = 3.64). Lack of premeditation and delay discounting were the most relevant facets in high-risk trajectories. Selective intervention and more intense and tailored treatment might help these adolescents to reduce early increases in impulsivity and prevent escalation of substance use.