Postdoctoral Fellow The University of Chicago CHICAGO, Illinois, United States
Background: Stimulants such as methamphetamine, are the second most commonly used illicit drugs. Stimulants activate reward circuitry in the brain, and are associated with the development of substance abuse. More research is needed however, on the pharmacodynamic effects of acute stimulant exposure, such as changes in neural response to drug or non-drug rewards. In the current study, we examined how an acute oral dose of methamphetamine impacts neural response to monetary reward. Methods: In a within-subject, randomized, double-blind, placebo-controlled study, healthy volunteers (n=42) between the ages of 18-35 received an oral dose of placebo or methamphetamine (20mg) during two sessions. Participants completed a monetary incentive delay task during fMRI We determined the effects of methamphetamine on neural activation during anticipation of a monetary reward and reward outcome, in regions of interest including the ventral striatum, caudate, putamen, and OFC/vmPFC. In exploratory analysis, we also examined changes in whole-brain activation during anticipation and outcome of reward phases. Results: Methamphetamine increased BOLD activation in the ventral striatum (p=0.04) for win + loss trials > neutral trials, during anticipation of reward. Methamphetamine did not significantly alter BOLD activation for reward outcome in any regions of interest. Exploratory whole brain analysis with threshold set to p< 0.001 revealed no significant drug effects on BOLD signal for either anticipation or outcome of reward. Conclusion: Our results suggest that methamphetamine increases neural response in reward circuitry in anticipation of a monetary reward or loss, regardless of valence. This study provides insight on pharmacodynamic effects of stimulant exposure on changes in immediate brain activity in response to non-drug reward.
