Discounting Task Research Articles

Measuring self-control in a wild songbird using a spatial discounting task

Self-control allows animals to resist instant gratification and invest more time and/or energy in better outcomes. However, widespread temporal self-control tasks lack ecological validity for many species, and few studies have explored whether self-control can be measured in the wild. We used a spatial discounting task resembling natural foraging decisions to measure self-control in wild toutouwai (Petroica longipes), a songbird endemic to New Zealand. Birds chose between a near, low-quality food item and a high-quality food item further away. Toutouwai showed striking individual variation in their self-control abilities. Validation tests suggested that our task reliably measured self-control in a spatial foraging context. However, individual-level performance was confounded by food preferences and the satiation and/or learning effects associated with increasing trial number, limiting the applicability of this task as a measure of individual variation in self-control. Nonetheless, we found no correlation between an individual’s self-control and their inhibitory control measured using a detour task, suggesting that self-control is a distinct ability from the suppression of impulsive motor actions in toutouwai. This study demonstrates for the first time that a bird is capable of self-control in a spatial context and provides suggestions for how future researchers may robustly quantify individual differences in self-control in the wild.

Associations Between Intertemporal Food Choice and BMI in Adult Women: An fMRI Study Using a Quasi-realistic Design.

Impulsivity resulting in unrestrained eating has been implicated as a contributing factor for obesity. Delay discounting (DD) tasks where individuals choose between a smaller immediate reward and a larger delayed reward provide useful data to describe impulsive decision-making and to determine the extent to which delayed rewards are discounted. To study the association between body mass index(BMI) and delay discounting for food and money in adult women. We used a DD task with real food rewards to investigate impulsive decision-making as related to BMI in participants who self-identified as women. Participants in group A had a mean BMI of 21.4 (n = 14), and participants in group B had a mean BMI of 32.2 (n = 14). Each group was tested in a hungry state during a single session. We performed fMRI during a DD task requiring participants to choose between a food item (one sandwich) constituting a smaller immediate reward and multiple food items (two, three, or four sandwiches) constituting a series of larger delayed rewards available at different intervals. The steepness of the discounting curve for food was determined from these decisions. Participants then completed a monetary discounting task to facilitate a comparison of the discounting of food and monetary rewards. Participants in group B discounted food rewards more steeply than monetary rewards. Decisions for delayed rewards led to increased activations of brain areas related to executive control on fMRI, such as the head of the caudate nucleus and the anterior cingulate cortex (ACC) in group A, but not group B participants. Our findings suggest that group B had difficulty deciding against the immediate food rewards due to insufficient recruitment of cortical control areas. Therefore, impulsivity is an important target for behavioral interventions in individuals with obesity.

Decision cost hypersensitivity underlies Huntington's disease apathy.

The neuropsychiatric syndrome of apathy is now recognized to be a common and disabling condition in Huntington's disease (HD). However, the mechanisms underlying it are poorly understood. One way to investigate apathy is to utilise a theoretical framework of normal motivated behaviour, to determine where breakdown has occurred in people with this behavioural disruption. A fundamental computation underlying motivated, goal-directed behaviour across species is weighing up the costs and rewards associated with actions. Here, we asked whether people with apathy are more sensitive to costs of actions (physical effort and time delay), less sensitive to rewarding outcomes, or both. Based on the unique anatomical substrates associated with HD pathology, we hypothesised that a general hypersensitivity to costs would underpin HD apathy. Genetically confirmed carriers of the expanded Huntingtin gene (premanifest to mild motor manifest disease (n=53) were compared to healthy controls (n = 38). Participants performed a physical effort-based decision-making task (Apple Gathering Task) and a delay discounting task (Money Choice Questionnaire). Choice data was analysed using linear regression and drift diffusion models that also accounted for the time taken to make decisions. Apathetic people with HD accepted fewer offers overall on the Apple Gathering Task, specifically driven by increased sensitivity to physical effort costs, and not explained by motor severity, mood, cognition, or medication. Drift diffusion modelling provided further evidence of effort hypersensitivity, with apathy associated with a faster drift rate towards rejecting offers as a function of varying effort. Increased delay sensitivity was also associated with apathy, both when analysing raw choice and also drift rate, where there was moderate evidence of HD apathy drifting faster towards the immediately available (low cost) option. Furthermore, the effort and delay sensitivity parameters from these tasks were positively correlated. The results demonstrate a clear mechanism for apathy in HD, cost hypersensitivity, which manifests in both the effort and time costs associated with actions towards rewarding goals. This suggests that HD pathology may cause a domain-general disruption of cost processing, which is distinct to apathy occurrence in other brain disorders, and may require different therapeutic approaches.

Predictors of Change in Vaccination Decisions Among the Vaccine Hesitant: Examining the Roles of Age and Intolerance of Uncertainty.

Vaccine hesitancy and resistance pose significant threats to controlling pandemics and preventing infectious diseases. In a group of individuals unvaccinated against the disease caused by the SARS-CoV-2 coronavirus (COVID-19), we investigated how age, intolerance of uncertainty (IU), and their interaction affected the likelihood of having changed one's vaccination decision a year later. We hypothesized that higher IU would increase the likelihood of becoming vaccinated, particularly among individuals of younger age. We predicted that this effect would remain significant, even after controlling for delay discounting and trust in science. The goal of this research was to understand the factors influencing changes in vaccination decisions among the vaccine hesitant. In a larger longitudinal study, ~7,500 participants from Prolific.co completed demographic and vaccination status questions, a delay discounting task, and the Intolerance of Uncertainty Scale in June-August 2021. Approximately 3,200 participants completed a follow-up survey in July-August 2022, answering questions about vaccination status, reasons for vaccination decision, and trust in science. We analyzed data from 251 participants who initially had no intention of getting vaccinated and completed the follow-up survey; 38% reported becoming vaccinated in the intervening year. Data were analyzed using multilevel logistic regression. Over and above other factors related to vaccination decisions (delay discounting, trust in science), younger participants were more likely to change their decision and become vaccinated a year later, especially if they had higher IU, confirming our predictions. Primary reasons for becoming vaccinated were necessity and seeking protection against the virus. These findings highlight the complex interplay between age, uncertainty, and vaccination decisions, and inform health policies by suggesting the need for tailoring interventions to specific concerns in different age groups.

Exercise recovers weight gain, but not increased impulsive choice, caused by a high-fat diet

A high-fat diet has negative effects on physical, neurological, and behavioral outcomes. One consistent finding is that a diet high in fat increases impulsive choice behavior—behavior that is linked to a wide range of other negative health behaviors. While the mechanism for this increase in impulsive choice is not well understood, exercise, with its well-known and many benefits, may serve as an effective and accessible way to combat increased impulsive choice associated with a high-fat diet. The goal of this work was to test this possibility. Rats were divided into four groups in a two-by-two factorial design: exercise and control diet, sedentary and control diet, exercise and high-fat diet, sedentary and high-fat diet. Rats in the exercise groups engaged in 30-min of forced, moderate intensity wheel-running exercise five days per week. Rats in the high-fat diet groups ate a diet high in fat. Impulsive choice was measured using a delay discounting task. Exercise prevented weight gain associated with the high-fat diet. Exercise also preserved relative motivation for food reinforcement. However, exercise did not prevent increases in impulsive choice observed for rats that consumed a high-fat diet relative to the rats that consumed the control diet. This work rules out several possible mechanisms by which a high-fat diet may increase impulsive choice behavior. It makes clear that exercise alone may not stave off increases in impulsive choice caused by a high-fat diet. Future work is necessary to uncover the underlying mechanism for this effect and discover interventions, perhaps ones that combine both physically and cognitively demanding activities, to improve health and behavior as it relates to decision making processes.

The role of impulsivity and binge eating in outpatients with overweight or obesity: an EEG temporal discounting study

BackgroundBinge eating (BE) is associated with a range of cognitive control deficits related to impulsivity, including lower response inhibition, preference for immediate gratification, and maladaptive decision-making. The aim was to investigate whether impulsivity and BE may interact with the decision process and underlying brain activity in outpatients with overweight or obesity who are starting a treatment to achieve weight loss.MethodsA sample of 26 treatment-seeking outpatients with overweight or obesity was evaluated for impulsivity, BE, and temporal discounting rates. Impulsivity was measured with the Barratt Impulsiveness Scale (BIS-11), according to which two groups were composed: high BIS and low BIS; BE was assessed with the eating disorders module of the Structured Clinical Interview for DSM5—Research Version, according to which two groups were composed: with (BE group) or without BE (NBE group). Changes in subjective value of rewards were measured with the Temporal Discounting Task (TDt) where participants had to choice between sooner but smaller vs. later but larger monetary rewards. These choices were made in two differently delayed conditions (“Now” and “Not-now”). Brain rhythms were recorded through high-density electroencephalogram (hd-EEG) during the TDt.ResultsPatients with BE reported more impulsive tendencies and perceived sooner rewards as more gratifying when both options were delayed (Not-now condition, p = 0.02). The reward choice in the TDt was accompanied by a general EEG alpha band desynchronization in parietal areas observed without differences between experimental conditions and patients groups. No effects were observed within the Now condition or in the other EEG bands.ConclusionsThe tendency to favor immediate rewards may constitute an obstacle to adhering to treatment plans and achieving weight loss goals for outpatients with overweight or obesity. Clinicians are therefore encouraged to include psychological factors, such as impulsivity and dysfunctional eating behaviors, when designing weight loss programs. By addressing these psychological aspects, clinicians can better support patients in overcoming barriers to adherence and achieving sustainable weight loss.Trial registrationThis study was approved by the Ethics Committee of the Department of Psychological, Health, and Territorial Sciences of the University G. d’Annunzio of Chieti-Pescara (Prot. n. 254 of 03/14/2017).

Relationship Between Delay Discounting and Clinical Diabetes Outcomes: A Systematic Review.

To evaluate the evidence on the relationship between delay discounting and clinical diabetes outcomes, identify current measures, and recommend areas for future work. A reproducible search using OVID Medline, PsycINFO, PubMed, Science Direct, and Scopus was conducted. Articles published from database creation up to March 2024 were searched. Medical Subject Heading (MeSH) terms and keywords representing delay discounting and diabetes were used. Outcomes included hemoglobin A1c (HbA1c), LDL, body mass index (BMI), blood pressure, quality of life (QOL), psychosocial factors, self-care behaviors, and diabetes complications. A total of 15 articles met the inclusion criteria and were included for final synthesis. Overall, 14 studies included in this review found a significant relationship between delay discounting and diabetes-related outcomes, such that higher delay discounting is significantly related to worse diabetes outcomes for HbA1c, self-care behaviors, BMI, stress, and quality of life across self-reported measures of delay discounting and delay discounting tasks. Evidence supports the relationship between delay discounting and diabetes-related outcomes and self-care behaviors across measures of delay discounting and type of diabetes. To understand delay discounting as a mechanism driving diabetes outcomes and to develop targeted interventions, additional work using a multidisciplinary approach is needed to validate the construct, identify pathways, and refine intervention approaches that can be tested to improve population health.

Cortico-striatal beta oscillations as a reward-related signal

The value associated with reward is sensitive to external factors, such as the time between the choice and reward delivery as classically manipulated in temporal discounting tasks. Subjective preference for two reward options is dependent on objective variables of reward magnitude and reward delay. Single neuron correlates of reward value have been observed in regions, including ventral striatum, orbital, and medial prefrontal cortex. Brain imaging studies show cortico-striatal-limbic network activity related to subjective preferences. To explore how oscillatory dynamics represent reward processing across brain regions, we measured local field potentials of rats performing a temporal discounting task. Our goal was to use a data-driven approach to identify an electrophysiological marker that correlates with reward preference. We found that reward-locked oscillations at beta frequencies signaled the magnitude of reward and decayed with longer temporal delays. Electrodes in orbitofrontal/medial prefrontal cortex, anterior insula, ventral striatum, and amygdala individually increased power and were functionally connected at beta frequencies during reward outcome. Beta power during reward outcome correlated with subjective value as defined by a computational model fit to the discounting behavior. These data suggest that cortico-striatal beta oscillations are a reward signal correlated, which may represent subjective value and hold potential to serve as a biomarker and potential therapeutic target.

Anxiety sensitivity is associated with heightened intolerance of uncertainty in individuals with alcohol use disorder.

Alcohol use disorder (AUD) is a highly prevalent, yet heterogenous condition linked to anxiety, reward sensitivity, and cognitive biases. Understanding cognitive mechanisms of specific AUD symptoms is crucial for developing tailored, effective interventions. This pilot study sought to assess whether two potential cognitive correlates of AUD-intolerance of uncertainty and delay discounting-differentially influence the relationship between AUD, anxiety sensitivity, and drinking motives. Individuals with mild-to-moderate AUD (n = 31) and healthy control participants (n = 31) completed a single-session lab study in which they performed a decision making under uncertainty task as a behavioral measure of uncertainty tolerance, completed a delay discounting task as a measure of reward sensitivity, and responded to surveys related to anxiety sensitivity, state and trait anxiety, intolerance of uncertainty, and drinking motives. Hierarchical regression results demonstrated a significant interaction between AUD status (AUD vs. control) on both self-reported (β = 0.687, p = .020) and behavioral (β = 0.777, p = .012) intolerance of uncertainty. Greater anxiety sensitivity was associated with heightened intolerance of uncertainty in those with AUD but not controls. Correlations showed that the coping drinking motive was significantly positively associated with anxiety sensitivity (r = 0.462, p = .010), self-reported (r = 0.535, p = .002), and behavioral intolerance of uncertainty (r = 0.396, p < .027) in participants with AUD but not controls. No significant associations between anxiety sensitivity, drinking motives, and delay discounting were observed in either the AUD or the control group. Intolerance of uncertainty may therefore represent a cognitive bias in which individuals with AUD and anxiety sensitivity drink to cope with environmental and internal uncertainty. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Episodic future thinking improves intertemporal choice and food choice in individuals with higher weight: A systematic review and meta-analysis.

Episodic future thinking (EFT) strengthens self-regulation abilities by increasing the perceived value of long-term reinforcements and reducing impulsive choice in delay discounting tasks. As such, EFT interventions have the potential to improve dietary and eating-related decision-making in individuals with obesity or binge eating symptoms, conditions associated with elevated delay discounting. Here, we meta-analyzed evidence from 12 studies that assessed whether EFT interventions improve delay discounting and real-world food choice compared to control interventions. Included studies involved 951 adults with overweight or obesity (body mass index [BMI] ≥25). There were no studies involving participants with binge eating disorder. EFT intervention pooled effects were significant, improving delay discounting with a medium effect, g = 0.55, p < 0.0001, and subsequent food choice outcomes with a small effect, g = 0.31, p < 0.01. Notably, our review is the first to analyze mechanisms of effect in this population, demonstrating that improvements were greater when temporal horizons of EFT episodes were aligned with delay discounting tasks and more distant horizons predicted far-transfer to subsequent dietary and eating-related choices. Our findings thus show that EFT is an effective intervention for individuals with higher weight at risk of adverse health consequences.

The impact of subclinical psychotic symptoms on delay and effort discounting: Insights from behavioral, computational, and electrophysiological methods

BackgroundThe ability to value rewards is crucial for adaptive behavior and is influenced by the time and effort required to obtain them. Impairments in these computations have been observed in patients with schizophrenia and may be present in individuals with subclinical psychotic symptoms (PS). MethodsIn this study, we employed delay and effort-discounting tasks with food rewards in thirty-nine participants divided into high and low levels of PS. We investigated the underlying mechanisms of effort-discounting through computational modelling of dopamine prefrontal and subcortical circuits and the electrophysiological biomarker of both delay and effort-discounting alterations through resting-state frontal alpha asymmetry (FAA). ResultsResults revealed greater delay discounting in the High PS group compared to the Low PS group but no differences in the effort discounting task. However, in this task, the same levels of estimated dopamine release were associated with a lower willingness to exert effort for high-calorie food rewards in High PS participants compared to Low PS participants. Although there were no significant differences in FAA between the High PS and Low PS groups, FAA was significantly associated with the severity of participants' negative symptoms. ConclusionsOur study suggests that the dysfunction in temporal and effort cost computations, seen in patients with schizophrenia, may be present in individuals with subclinical PS. These findings provide valuable insight into the early vulnerability markers (behavioral, computational, and electrophysiological) for psychosis, which may aid in the development of preventive interventions. These findings are preliminary and warrant further investigation.

Time on social networking sites is associated with impulsive decision-making

ABSTRACT Almost five billion individuals worldwide use social networking sites (SNSs) such as Instagram, Facebook, Snapchat, and X (formerly known as Twitter). The social rewards obtained on these sites induce users to spend substantial durations of time on them. However, current research demonstrates mixed findings on whether greater time on SNSs is related to riskier decision-making and impulsive tendencies. To address these findings, we conducted an online study (n = 225) to assess how time across four SNSs relates to impulsive decision-making in the delay discounting task. We included each trial as an individual choice in a regression model predicting preference for the immediate reward, for a total of 20,265 choices. Greater average time across all SNSs was related with a higher likelihood of choosing the immediate, but smaller, reward. In other words, people who spent more time on SNSs also made more impulsive decisions. When including individual platforms, greater time on Instagram and X, but not Facebook or Snapchat, was related with a higher likelihood of choosing the immediate reward. These findings help clarify prior literature on the relationship between platform specific SNS use and impulsive decision-making. We discuss limitations, directions for future research, and broader implications for the field.

Associations between PTSD and temporal discounting: The role of future thinking

Background and objectivesDespite documented alterations in future thinking in posttraumatic stress disorder (PTSD), our understanding of how individuals with PTSD make future-oriented decisions is limited. We tested the hypothesis that increased discounting in association with PTSD reflects failure to spontaneously envision future rewarding situations. MethodsThirty-seven trauma exposed war-zone veterans completed a standard temporal discounting task as well as a temporal discounting task accompanied by episodic future thinking cues. ResultsSeverity of PTSD symptoms was associated with preference for sooner, smaller rewards in the standard task. Consistent with our hypothesis, when participants engaged in future thinking, greater PTSD symptom severity was no longer associated with steeper discounting. Moreover, difficulty anticipating future events, as measured contemporaneously in a separate task (Verfaellie et al., 2024), mediated the relationship between PTSD symptom severity and degree of discounting in the standard task. Among PTSD symptom clusters, the severity of avoidance and negative alterations in cognition and mood was related to steeper discounting. Measures of depression and alcohol use were not associated with discounting. LimitationsThe sample included mostly male, predominantly White veterans who experienced primarily combat-related trauma. ConclusionsPTSD-associated alterations in temporal discounting reflect failure to spontaneously imagine future positive events. Two common correlates of PTSD, depression and alcohol use, could not account for the observed associations between PTSD and future-oriented decisions.

Differential phase-amplitude coupling in nucleus accumbens and orbitofrontal cortex reflects decision-making during a delay discounting task

BackgroundThe impulsive choice is characterized by the preference for a small immediate reward over a bigger delayed one. The mechanisms underlying impulsive choices are linked to the activity in the Nucleus Accumbens (NAc), the orbitofrontal cortex (OFC), and the dorsolateral striatum (DLS). While the study of functional connectivity between brain areas has been key to understanding a variety of cognitive processes, it remains unclear whether functional connectivity differentiates impulsive-control decisions. MethodsTo study the functional connectivity both between and within NAc, OFC, and DLS during a delay discounting task, we concurrently recorded local field potential in NAc, OFC, and DLS in rats. We then quantified the degree of phase-amplitude coupling (PAC), coherence, and Granger Causality between oscillatory activities in animals exhibiting either a high (HI) or low (LI) tendency for impulsive choices. ResultsOur results showed a differential pattern of PAC during decision-making in OFC and NAc, but not in DLS. While theta-gamma PAC in OFC was associated with self-control decisions, a higher delta-gamma PAC in both OFC and NAc biased decisions toward impulsive choices in both HI and LI groups. Furthermore, during the reward event, Granger Causality analysis indicated a stronger NAc➔OFC gamma contribution in the HI group, while the LI group showed a higher OFC➔NAc gamma contribution. ConclusionsThe overactivity in NAc during reward in the HI group suggests that exacerbated contribution of NAcCore can lead to an overvaluation of reward that biases the behavior toward the impulsive choice.

In Parkinson's disease dopaminergic medication and deep brain stimulation of the subthalamic nucleus increase motor, but not reflection and cognitive impulsivity.

Parkinson's disease is associated with increased impulsivity, which can be divided into several domains: motor (consisting of proactive and reactive subdomains), reflection, and cognitive impulsivity. Evidence suggests that both dopaminergic medication and subthalamic nucleus deep brain stimulation can affect impulsivity. Therefore, we set out to investigate the effects of dopaminergic medication and subthalamic nucleus deep brain stimulation on motor, reflection, and cognitive impulsivity in Parkinson's disease patients. Twenty Parkinson's disease patients who underwent subthalamic nucleus deep brain stimulation were tested ON and OFF dopaminergic medication and ON and OFF subthalamic nucleus deep brain stimulation. They performed three different impulsivity tasks: the AX continuous performance task (AX-CPT) to test for motor impulsivity, the Beads task for reflection impulsivity, and the Delay discounting task for cognitive impulsivity. The combination of subthalamic nucleus deep brain stimulation and dopaminergic medication led to an increase in motor impulsivity (p = 0.036), both proactive (p = 0.045) and reactive (p = 0.006). There was no effect of either dopaminergic medication or subthalamic nucleus deep brain stimulation on reflection and cognitive impulsivity. The combination of dopaminergic medication and subthalamic nucleus deep brain stimulation leads to increased motor, but not cognitive or reflection, impulsivity in patients with Parkinson's disease. Both proactive and reactive motor impulsivity were impaired by the combination of dopaminergic medication and subthalamic nucleus deep brain stimulation.

Validation of the Sexual Discounting Task for Use in Adolescents.

The Sexual Discounting Task (SDT) was developed to evaluate the effects of delay on decision making as it relates to sexual risk-taking behaviors. Though previously validated with other populations, including urban emerging adults, the current study sought to validate the SDT with adolescents. A sample of adolescents (N = 155; 61% female) between ages 14 and 21 (Mage = 19.5years) was recruited to complete the SDT (involving choices between immediate unprotected sex and delayed sex with a condom with hypothetical sexual partners) and the Delay Discounting Task (a delay discounting task for money outcomes). Additionally, they completed several self-report measures assessing demographics, sexual behavior, and sexual history. If the condom was readily available, respondents were more likely to use a condom for partners who were judged "most likely to have an STI" and for those that participants were "least likely to have sex with." Moreover, when a condom was not immediately available, greater self-reported sexual risk-taking was related to greater sexual discounting (i.e., greater effects of delay on decreasing condom use). Furthermore, sexual discounting was greater among partners deemed more desirable and those judged "least likely to have an STI." Differences in sexual discounting were significant after controlling for immediately available condom use. Findings from the current study suggest that the SDT is clinically meaningful for adolescents and is sensitive to factors that influence real-world decisions to use condoms. Future treatment and prevention should consider delay discounting as an important variable affecting sexual risk behavior.

Cannabis as a shareable commodity in a social discounting task.

Cannabis use and cannabis use disorder diagnoses continue to increase in United States college-aged students as more states legalize recreational cannabis. Previous studies have attempted to associate cannabis use with delay discount rates, which involves participants making choices for smaller sooner versus larger later hypothetical rewards. More smaller sooner choices result in higher discount rates and suggest increased impulsivity. Delay discounting studies have shown a significant, but small effect size with people who use cannabis more likely to choose the smaller sooner rewards, relative to people who do not use cannabis. The present study tested whether students with different experience using cannabis (people who currently use cannabis, people who formerly used cannabis, or people who never used cannabis) would be sensitive to sharing a proportion of hypothetical marijuana with another individual at a given social distance, as a putative measure for cannabis value. Results from two separate data sets showed that students classified as current cannabis users were significantly less likely to share a proportion of hypothetical marijuana across a range of social distances, relative to students that self-reported never using cannabis. Students classified as either former or current users were not statistically different. These results were consistent with previous delay discounting results and showed a medium effect size (η² ≥ 0.10) for each data set, both separately and when combined. These results indicate that social distance is a meaningful variable that can be used in a modified discounting task to assess differential cannabis value in a student population who are increasingly susceptible to cannabis use disorder. These results may have future clinical implications. Social discount rates for cannabis may be able to differentiate individuals who will continue recreational use versus individuals that may develop cannabis dependence problems. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Assessing biomarkers of remission in female patients with anorexia nervosa (REMANO): a protocol for a prospective cohort study with a nested case–control study using clinical, neurocognitive, biological, genetic, epigenetic and neuroimaging markers in a French specialised inpatient unit

BackgroundAnorexia nervosa (AN) is a severe psychiatric disorder associated with frequent relapses and variability in treatment responses. Previous literature suggested that such variability is influenced by premorbid vulnerabilities such as...

Effects of delay sequence in a delay discounting task

Delay discounting refers to the decrease in subjective value of a reward as the delay until its receipt increases. In the present study we assessed the effects of the sequence of delay blocks (increasing or decreasing) on discounting and the data systematicity using a titrating procedure with human participants. All participants completed the delay discounting task in both an increasing and decreasing sequence of delays. Delays ranged from one day to ten years. We found steeper discounting when the delays were presented in an increasing sequence compared with when they were presented in a decreasing sequence. We also found steeper discounting when participants completed the increasing sequence condition first. Our results agree with other findings reported in the literature and suggest that delay discounting may be affected by prior and subsequent experience.

Methylphenidate, but not citalopram, decreases impulsive choice in rats performing a temporal discounting task.

Drugs targeting monoamine systems remain the most common treatment for disorders with impulse control impairments. There is a body of literature suggesting that drugs affecting serotonin reuptake and dopamine reuptake can modulate distinct aspects of impulsivity - though such tests are often performed using distinct behavioral tasks prohibiting easy comparisons. Here, we directly compare pharmacologic agents that affect dopamine (methylphenidate) vs serotonin (citalopram) manipulations on choice impulsivity in a temporal discounting task where rats could choose between a small, immediate reward or a large reward delayed at either 2 or 10s. In control conditions, rats preferred the large reward at a small (2s) delay and discounted the large reward at a long (10s) delay. Methylphenidate, a dopamine transport inhibitor that blocks reuptake of dopamine, dose-dependently increased large reward preference in the long delay (10s) block. Citalopram, a selective serotonin reuptake inhibitor, had no effect on temporal discounting behavior. Impulsive behavior on the temporal discounting task was at least partially mediated by the nucleus accumbens shell. Bilateral lesions to the nucleus accumbens shell reduced choice impulsivity during the long delay (10s) block. Following lesions, methylphenidate did not impact impulsivity. Our results suggest that striatal dopaminergic systems modulate choice impulsivity via actions within the nucleus accumbens shell, whereas serotonin systems may regulate different aspects of behavioral inhibition/impulsivity.