Background-Excessive discounting of future rewards has been observed in a variety of disorders and has been linked to both the valuation of the past, and memory of past events.

We review behavioral-and neuroeconomic research that identifies temporal discounting as an important component in the development and maintenance of drug addiction. First we review behavioral economic research that explains and documents the contribution of temporal discounting to addiction. This is followed with recent insights from neuroeconomics that may provide an explanation of why drug dependent individuals discount the future. Specifically, neuroeconomics has identified two competing neural systems that are related to temporal discounting using brainimaging techniques that examine the relative activation of different brain regions for temporal discounting. According to the competing neural systems account, choices for delayed outcomes are related to the prefrontal cortex (i.e., the "executive system") and choices for immediate outcomes are related to the limbic brain regions (i.e., the "impulsive system"). Temporal discounting provides a useful framework for future imaging research, and suggests a novel approach to designing effective drug dependence prevention and treatment programs.

Intertemporal choice is predicated on the valuation of commodities with respect to delay until their receipt. Subjective value of a future outcome decreases, or is discounted, as a function of that delay . Although behavioral studies suggest no difference between the devaluation of real and fictive outcomes, no neuroimaging studies have investigated potential differences in the underlying deliberative process. Here, we compare behavioral and neural correlates of intertemporal valuation of real and hypothetical monetary gains as well as hypothetical losses, which have been posited to involve different mechanisms. Behavioral and neuroimaging sessions were conducted in which participants made intertemporal choice decisions in a gains condition using both real and hypothetical $100 money and in a loss condition using a fictive $100 money. Within-subject comparison of behavioral data revealed no significant difference between levels of discounting across the three conditions. Random-effects analysis of functional magnetic resonance imaging (fMRI) data of each of the three discounting conditions independently revealed significant signal change in limbic (anterior cingulate, striatum, posterior cingulate) and executive functioning areas (lateral prefrontal cortex), whereas a repeated-measures ANOVA failed to detect differences in signal change across the three discounting conditions after correcting for multiple comparisons. These data support a concordance between real and hypothetical conditions from delay-discounting studies and further suggest a congruence of the fMRI blood oxygen level-dependent signal across brain regions associated with the deliberative process of different forms of intertemporal choice.

Tobacco use disproportionately affects lower socioeconomic status (SES) groups. Current explanations as to why lower SES groups respond less robustly to tobacco control efforts and tobacco dependence treatment do not fully account for this disparity. The identification of factors that predict relapse in this population might help to clarify these differences. Good candidates for novel prognostic factors include the constellation of behaviors associated with executive function including self-control/impulsiveness, the propensity to delay reward, and consideration and planning of future events. This study examined the ability of several measures of executive function and other key clinical, psychological, and cognitive factors to predict abstinence for highly dependent lower SES participants enrolled in intensive cognitive-behavioral treatment for tobacco dependence. Consistent with predictions, increased discounting and impulsiveness, an external locus of control as well as greater levels of nicotine dependence, stress, and smoking for negative affect reduction predicted relapse. These findings suggest that these novel factors are clinically relevant in predicting treatment outcomes and suggest new targets for therapeutic assessment and treatment approaches.

Background Impulsivity critically relates to many psychiatric disorders. Given the multi-faceted construct that impulsivity represents, defining core aspects of impulsivity is vital for the assessment and understanding of clinical conditions. Choice impulsivity (CI), involving the preferential selection of smaller sooner rewards over larger later rewards, represents one important type of impulsivity. Method The International Society for Research on Impulsivity (InSRI) convened to discuss the definition and assessment of CI and provide recommendations regarding measurement across species. Results Commonly used preclinical and clinical CI behavioral tasks are described, and considerations for each task are provided to guide CI task selection. Differences in assessment of CI (self-report, behavioral) and calculating CI indices (e.g., area-under-the-curve, indifference point, steepness of discounting curve) are discussed along with properties of specific behavioral tasks used in preclinical and clinical settings. Conclusions The InSRI group recommends inclusion of measures of CI in human studies examining impulsivity. Animal studies examining impulsivity should also include assessments of CI and these measures should be harmonized in accordance with human studies of the disorders being modeled in the preclinical investigations. The choice of specific CI measures to be included should be based on the goals of the study and existing preclinical and clinical literature using established CI measures.