Waiting Impulsivity: The Influence of Acute Methylphenidate and Feedback

Abstract

Background: The ability to wait and to weigh evidence is critical to behavioral regulation. These behaviors are known as waiting and reflection impulsivity. In Study 1, we examined the effects of methylphenidate, a dopamine and norepinephrine reuptake inhibitor, on waiting and reflection impulsivity in healthy young individuals. In study 2, we assessed the role of learning from feedback in disorders of addiction.

Methods: We used the recently developed 4-Choice Serial Reaction Time task and the Beads task. Twenty-eight healthy volunteers were tested twice in a randomized, double-blind, placebo-controlled cross-over trial with 20mg methylphenidate. In the second study, we analyzed premature responses as a function of prior feedback in disorders of addiction.

Results: Study 1: Methylphenidate was associated with greater waiting impulsivity to a cue predicting reward along with faster responding to target onset without a generalized effect on reaction time or attention. Methylphenidate influenced reflection impulsivity based on baseline impulsivity. Study 2: More premature responses occurred after premature responses in stimulant-dependent subjects.

Conclusions: We show that methylphenidate has dissociable effects on waiting and reflection impulsivity. Chronic stimulant exposure impairs learning from prior premature responses, suggesting a failure to learn that premature responding is suboptimal. These findings provide a greater mechanistic understanding of waiting impulsivity.

Keywords: addiction; binge drinking; impulsivity; methylphenidate; premature responding; stimulant dependence.

Figure 1.

Premature responding task and outcomes. 4-Choice Serial Reaction Time task (4-CSRT). Reaction time (RT) was measured as the RT from green target onset to release of space bar; Movement time (MT) was measured as the RT from release of the space bar to touching the screen. The graph represents premature responses in healthy individuals on methylphenidate (MPH) or placebo. Higher premature responding represents greater impulsivity. Error bars represent between subject standard error of the mean. *P<.05

Figure 2.

Secondary outcomes of premature responding task. (A) Reaction time (RT; left: RT = time from target onset to release of space bar) and movement time (right: MT = time from release of space bar to touching the screen) in healthy individuals on methylphenidate (MPH) or placebo. (B) Ratio of premature responses following monetary loss (left) and prior premature response (right). Error bars represent between subject standard error of the mean. *P<.05, ♮P=.065.

Figure 3.

Reflection impulsivity task. Beads task. The graph represents the number of beads or evidence accumulated in healthy individuals on methylphenidate (MPH) or placebo as a function of high or low reflection impulsivity at baseline on placebo. Lower number of beads represents greater impulsivity. Error bars represent between subject standard error of the mean. *P<.001

Figure 4.

Premature response following feedback. (A) Ratio of premature responses following a premature response comparing healthy volunteers (HV), subjects abstinent from methamphetamine dependence (Stim) and alcohol use disorders (AUDs) and in binge drinkers (BDs) and obese subjects with and without binge eating disorder (BED). Ratio of premature responses following monetary loss (B) and following a monetary win (C).