Development of a Novel Trial-by-Trial Consequence Human Delay Discounting Task

Johns Hopkins University, Baltimore MD

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Abstract

DESCRIPTION (provided by applicant): Delay discounting is a behavioral model of impulsivity that indexes an individual's relative preference for smaller sooner over larger later rewards. It therefore models a fundamental behavior in drug dependence: choosing the immediate but short-lived euphoric effects of drug use over the delayed but more valuable improvements in health and social functioning that come with sustained abstinence. The relation between delay discounting and drug abuse has been studied in both human and nonhuman animal research. However, a concern remains whether human and nonhuman animal delay discounting tasks assess the same processes. Both human and nonhuman animal studies typically involve presenting a series of choices between a small immediate reward and a larger delayed reward. However, nonhuman animal discounting tasks involve trial-by-trial consequences, which require the subject to experience contingent delays and reward delivery with every choice trial. Human discounting tasks typically involve hypothetical consequences. Although "potentially real reward" methods that have been used in human research provide actual consequences for randomly selected choice trials, those consequences are delivered after the entire task is finished. Therefore, with potentially real reward methods, participants'choices are influenced by the promise or anticipation of contingent consequences, rather than direct operant experience within the session that can influence choice behavior on subsequent trials. Given the wealth of nonhuman animal delay discounting data relevant to drug abuse, it would facilitate translational research to have available human discounting methods that are more closely related to nonhuman animal methods. Therefore, an important scientific step in using delay discounting to investigate impulsive decision making in drug abusing individuals is to develop methods for assessing discounting in humans with trial-by-trial consequences. Although a few human discounting procedures have been developed that employ trial-by-trial consequences, the procedure to be piloted in the proposed study may have advantages over these existing procedures, including shorter task duration, the lack of probabilistic reinforcement as a confound, and guaranteed determinacy of data points. Because delay discounting procedures in the study of drug abuse have involved both drug abusing individuals and non-drug abusing individuals, this novel delay discounting procedure will be developed with cocaine dependent individuals and demographically matched non-drug dependent individuals. An extended battery of previously utilized delay discounting conditions involving hypothetical and potentially real rewards, as well as a questionnaire measure of impulsivity, will be assessed for comparison with the novel task. The comparison of all discounting measures between groups may provide trends that warrant a future larger study comparing these groups with this set of discounting tasks. Ultimately, this project may provide a powerful tool in the study of impulsivity in drug dependence, and provide important information on cocaine dependence and impulsivity. PUBLIC HEALTH RELEVANCE: A behavioral study in cocaine dependent individuals and non-drug dependent control individuals will be used to develop a novel procedure for studying impulsive decision making in drug abuse. A wide range of existing behavioral impulsivity measures will be assessed that will extend our understanding of impaired decision making associated with cocaine abuse. Because impulsivity resulting from cocaine abuse is known to result in public health harms, including the spread of HIV, through impulsive behavior, this study should ultimately lead to important information for cocaine prevention and treatment efforts.