Individual differences in discount rate are associated with demand for self‐administered cocaine, but not sucrose

Substance abusers, including cocaine abusers, discount delayed rewards to a greater extent than do matched controls. In the current experiment, individual differences in discounting of delayed rewards in rats (choice of one immediate over three delayed sucrose pellets) were assessed for associations with demand for either sucrose pellets or an intravenous dose of 0.1 mg/kg/infusion cocaine. Twenty‐four male Sprague Dawley rats were split into three groups based on sensitivity to delay to reinforcement. Then, demand for sucrose pellets and cocaine was determined across a range of fixed‐ratio values. Delay discounting was then reassessed to determine the stability of this measure over the course of the experiment. Individual differences in impulsive choice were positively associated with elasticity of demand for cocaine, a measure of reinforcer value, indicating that rats having higher discount rates also valued cocaine more. Impulsive choice was not associated with the level of cocaine consumption as price approached 0 or with any parameter associated with demand for sucrose. Individual sensitivity to delay was correlated with the initial assessment when reassessed at the end of the experiment, although impulsive choice increased for this cohort of rats as a whole. These findings suggest that impulsive choice in rats is positively associated with valuation of cocaine, but not sucrose.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95135/1/adb361.pd

Assessing Animal Models of Impulsive Behavior: Inter-Model Congruity, Relationship to Demand for Cocaine, and Effects of Selective Dopaminergic Compounds.

Valuing immediate rewards and acting quickly to obtain those rewards is often the optimal strategy. It is when such opportunistic strategies become excessive and disadvantageous that behavior is deemed impulsive. Psychological disorders such as attention-deficit/hyperactivity disorder and substance abuse are considered impulse-control disorders, and people that have been diagnosed with these disorders have been shown to exhibit impulsive behavior patterns. People with impulse-control disorders also have abnormal levels of neural activity in key areas of the brain that use the neurotransmitter dopamine. Numerous models exist for the study of impulsive behavior in laboratory animals, but in many cases the relevance of these models to the human condition is unclear. A multi-faceted approach was taken to assess the construct and predictive validity of chosen animal models of impulsivity. Assessed first was whether individual differences in the performance of rats on the delay discounting task, a model of impulsive choice, was associated with individual differences in self-administered cocaine injections. Since substance abusers are known to be more impulsive on the version of the delay discounting task used in humans, it was predicted that impulsive choice in rats would be associated with drug demand, a measure of reward value. Results confirmed that impulsive choice was associated with demand for cocaine, but not for sucrose in a control condition. The delay discounting task, a paced fixed consecutive number schedule, and the uncertain visual discrimination task are purported models of impulsive choice, impulsive action, and impulsive preparation, respectively. Drugs that preferentially act at different populations of dopamine receptors were administered to separate groups of rats performing on each of these tasks to assess the theoretical and clinical relevance of each. Receptor-specific modulation of impulsive behavior was found on each task. Finally, inter-model congruity of the same three tasks was assessed in a within-subjects design to determine if individual differences in performance correlated across tasks. Selected drugs were also given to the same subjects trained on multiple tasks to assess whether individual variation in drug effects correlated across tasks. Results did not fully support the classification of these tasks into three distinct subtypes of impulsivity.Ph.D.PsychologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/64763/1/mickyk_1.pd

Stuck in Time: Negative Income Shock Constricts the Temporal Window of Valuation Spanning the Future and the Past

Insufficient resources are associated with negative consequences including decreased valuation of future reinforcers. To determine if these effects result from scarcity, we examined the consequences of acute, abrupt changes in resource availability on delay discounting-the subjective devaluation of rewards as delay to receipt increases. In the current study, 599 individuals recruited from Amazon Mechanical Turk read a narrative of a sudden change (positive, neutral, or negative) to one\u27s hypothetical future income and completed a delay discounting task examining future and past monetary gains and losses. The effects of the explicit zero procedure, a framing manipulation, was also examined. Negative income shock significantly increased discounting rates for gains and loses occurring both in the future and the past. Positive income windfalls significantly decreased discounting to a lesser extent. The framing procedure significantly reduced discounting under all conditions. Negative income shocks may result in short-term choices

Choice Bundling Increases Valuation of Delayed Losses More Than Gains in Cigarette Smokers

Choice bundling, in which a single choice produces a series of repeating consequences over time, increases valuation of delayed monetary and non-monetary gains. Interventions derived from this manipulation may be an effective method for mitigating the elevated delay discounting rates observed in cigarette smokers. No prior work, however, has investigated whether the effects of choice bundling generalize to reward losses. In the present study, an online panel of cigarette smokers (N = 302), recruited using survey firms Ipsos and InnovateMR, completed assessments for either monetary gains or losses (randomly assigned). In Step 1, participants completed a delay-discounting task to establish Effective Delay 50 (ED50), or the delay required for an outcome to lose half of its value. In Step 2, participants completed three conditions of an adjusting-amount task, choosing between a smaller, sooner (SS) adjusting amount and a larger, later (LL) fixed amount. The bundle size (i.e., number of consequences) was manipulated across conditions, where a single choice produced either 1 (control), 3, or 9 consequences over time (ascending/descending order counterbalanced). The delay to the first LL amount in each condition, as well as the intervals between all additional SS and LL amounts (where applicable), were set to individual participants’ ED50 values from Step 1 to control for differences in discounting of gains and losses. Results from Step 1 showed significantly higher ED50 values (i.e., less discounting) for losses compared to gains (p \u3c 0.001). Results from Step 2 showed that choice bundling significantly increased valuation of both LL gains and losses (p \u3c 0.001), although effects were significantly greater for losses (p \u3c 0.01). Sensitivity analyses replicated these conclusions. Future research should examine the potential clinical utility of choice bundling, such as development of motivational interventions that emphasize both the bundled health gains associated with smoking cessation and the health losses associated with continued smoking

Cocaine-Dependent Adults and Recreational Cocaine Users Are More Likely Than Controls to Choose Immediate Unsafe Sex Over Delayed Safer Sex

Cocaine users have a higher incidence of risky sexual behavior and HIV infection than non-users. Our aim was to measure whether safer-sex discount rates, a measure of the likelihood of having immediate unprotected sex versus waiting to have safer sex, differed between controls and cocaine users of varying severity. Of the 162 individuals included in the primary data analyses, 69 met DSM-IV-TR criteria for cocaine dependence, 29 were recreational cocaine users who did not meet dependence, and 64 were controls. Participants completed the sexual delay discounting task, which measures one’s likelihood of using a condom when immediately available and how that likelihood decreases as a function of delay to condom availability with regard to four images chosen by the participants of hypothetical sexual partners differing in perceived desirability and likelihood of having a sexually-transmitted infection. When a condom was immediately available, stated likelihood of condom use sometimes differed between cocaine users and controls, which depended on the image condition. Even after controlling for rates of condom use when immediately available, the Cocaine Dependent and Recreational Users groups were more sensitive to delay to condom availability than controls. Safer-sex discount rates were also related to intelligence scores. The sexual discounting task identifies delay as a key variable that impacts the likelihood of using a condom among these groups and suggests that HIV-prevention efforts may be differentially effective based on an individual’s safer-sex discount rate

Behavioral Economic Measurement of Cigarette Demand: A Descriptive Review of Published Approaches to the Cigarette Purchase Task

The cigarette purchase task (CPT) is a behavioral economic method for assessing demand for cigarettes. Growing interest in behavioral correlates of tobacco use in clinical and general populations as well as empirical efforts to inform policy has seen an increase in published articles employing the CPT. Accordingly, an examination of the published methods and procedures for obtaining these behavioral economic metrics is timely. The purpose of this investigation was to provide a review of published approaches to using the CPT. We searched specific Boolean operators ([“behavioral economic” AND “purchase task”] OR [“demand” AND “cigarette”]) and identified 49 empirical articles published through the year 2018 that reported administering a CPT. Articles were coded for participant characteristics (e.g., sample size, population type, age), CPT task structure (e.g., price framing, number and sequence of prices; vignettes, contextual factors), and data analytic approach (e.g., method of generating indices of cigarette demand). Results of this review indicate no standard approach to administering the CPT and underscore the need for replicability of these behavioral economic measures for the purpose of guiding clinical and policy decisions

A dual-process approach to exploring the role of delay discounting in obesity

Delay discounting of financial rewards has been related to overeating and obesity. Neuropsychological evidence supports a dual-system account of both discounting and overeating behaviour where the degree of impulsive decision making is determined by the relative strength of reward desire and executive control. A dual-parameter model of discounting behaviour is consistent with this theory. In this study, the fit of the commonly used one-parameter model was compared to a new dual-parameter model for the first time in a sample of adults with wide ranging BMI. Delay discounting data from 79 males and females (Males=26) across a wide age (M=28.44 years (SD=8.81)) and BMI range (M=25.42 (SD=5.16)) was analysed. A dual-parameter model (saturating-hyperbolic; Doya, 2008) was applied to the data and compared on model fit indices to the single-parameter model. Discounting was significantly greater in the overweight/obese participants using both models, however, the two parameter model showed a superior fit to data (p<.0001). The two parameters were shown to be related yet distinct measures consistent with a dual-system account of inter-temporal choice behaviour.The dual-parameter model showed superior fit to data and the two parameters were shown to be related yet distinct indices sensitive to differences between weight groups. Findings are discussed in terms of the impulsive reward and executive control systems that contribute to unhealthy food choice and within the context of obesity related research

Effects of methylphenidate on attention in Wistar rats treated with the neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4)

The aim of this study was to assess the effects of the neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4) on attention in rats as measured using the 5-choice-serial-reaction-time task (5CSRTT) and to investigate whether methylphenidate has effects on DSP4-treated rats. Methylphenidate is a noradrenaline and dopamine reuptake inhibitor and commonly used in the pharmacological treatment of individuals with attention deficit/hyperactivity disorder (ADHD). Wistar rats were trained in the 5CSRTT and treated with one of three doses of DSP4 or saline. Following the DSP4 treatment rats were injected with three doses of methylphenidate or saline and again tested in the 5CSRTT. The treatment with DSP4 caused a significant decline of performance in the number of correct responses and a decrease in response accuracy. A reduction in activity could also be observed. Whether or not the cognitive impairments are due to attention deficits or changes in explorative behaviour or activity remains to be investigated. The treatment with methylphenidate had no beneficial effect on the rats’ performance regardless of the DSP4 treatment. In the group without DSP4 treatment, methylphenidate led to a reduction in response accuracy and bidirectional effects in regard to parameters related to attention. These findings support the role of noradrenaline in modulating attention and call for further investigations concerning the effects of methylphenidate on attentional processes in rats

Estimating Uptake for Reduced-nicotine Cigarettes Using Behavioral Economics

This project contains supplementary materials for the article "Estimating Uptake for Reduced-nicotine Cigarettes Using Behavioral Economics" published in Tobacco Regulatory Science (https://doi.org/10.18001/TRS.5.3.5