Early and prolonged exposure to reward delay: Effects on impulsive choice and alcohol self-administration in male rats.

Abstract

Naturally occurring impulsive choice has been found to positively predict alcohol consumption in rats. However, the extent to which experimental manipulation of impulsive choice may modify alcohol consumption remains unclear. In the present study, we sought to: (a) train low levels of impulsive choice in rats using early, prolonged exposure to reward delay, and (b) determine the effects of this manipulation on subsequent alcohol consumption. During a prolonged training regimen, three groups of male, adolescent Long-Evans rats (21-22 days old at intake) responded on a single lever for food rewards delivered after either a progressively increasing delay, a fixed delay, or no delay. Post-tests of impulsive choice were conducted, as was an evaluation of alcohol consumption using a limited-access, two-bottle test. Following delay-exposure training, both groups of delay-exposed rats made significantly fewer impulsive choices than did rats in the no-delay group. In addition, fixed-delay rats consumed significantly more alcohol during daily, 30-min sessions than no-delay rats. Possible mechanisms of these effects are discussed, as is the significance of these findings to nonhuman models of addiction.

Mechanisms of impulsive choice: II. Time-based interventions to improve self-control

“…This suggests that timing precision, delay tolerance, and impulsive choice may all emerge from a common underlying factor. The current findings are also consistent with previous research demonstrating that exposure to reward and/or delay (Eisenberger and Adornetto 1986; Madden et al 2011; Stein et al 2013), and increased salience of delay (Zauberman et al 2009), can exert powerful effects on impulsive choice. However, these studies did not measure any concomitant effects on specific temporal processes.…”

“…Delay exposure could increase delay tolerance as the primary effect and improve the precision of timing as a secondary effect. Stein et al (2013) assessed the effect of exposure to either no delay, a fixed delay, or a progressively increasing delay on impulsive choice behavior. They found that exposure to either fixed or progressive delays increased LL choices compared to the no-delay condition, consistent with the present findings.…”

“…The co-occurrence of effects on timing and choice measures as a function of the intervention suggests that shared processes may be influencing timing precision and self-control, consistent with other recent research (Marshall et al 2014; McClure et al 2014). While impulsive choice has been previously mitigated with delay exposure techniques (Eisenberger et al 1982; Madden et al 2011; Stein et al 2013), increasing the salience of delays (Zauberman et al 2009), and exposure to both reward amounts and delays (Eisenberger and Adornetto 1986), the previous studies did not examine changes in timing behavior in conjunction with monitoring choice behavior.…”

“…This method results in moderate increases in LL preference (Binder et al 2000; Dixon et al 1998; Dixon and Holcomb 2000; Dixon, Rehfeldt, et al 2003; Mazur and Logue 1978; Neef et al 2001; Schweitzer and Sulzer-Azaroff 1995; Stein et al 2013). An alternative approach by Eisenberger and Adornetto (1986) examined the effect of exposure to the specific reward amounts and delays from an impulsive choice task by using the delay-amount combinations from the choice task as reinforcers for a variety of other tasks.…”

Working‐memory training: Effects on delay discounting in male long evans rats

“…To address the former, rats completed a working-memory assessment that was similar to the training task; the latter was addressed by exposing our rats to 140 sessions of WMT. Second, if WMT could be used to experimentally reduce delay discounting in rats, then this would provide an opportunity to evaluate the causal relation between differences in delay discounting and subsequent propensity for drug-taking (Stein et al, 2013). …”