Neural and behavioral mechanisms of impulsive choice in alcohol use disorder

Abstract

Background: Alcohol dependence has repeatedly been associated with impulsive choice, or the inability to choose large delayed rewards over smaller, but more immediate rewards. However, the neural basis of impulsive choice in alcohol use disorders (AUDs) is not well understood.

Methods: One hundred fifty-one individuals with a range of alcohol use from social drinking to severe alcohol dependence completed a delay discounting task while undergoing functional magnetic resonance imaging. Participants received customized trials designed to ensure an approximately equivalent number of immediate responses.

Results: Delaying gratification recruited regions involved in cognitive control, conflict monitoring, and the interpretation of somatic states. Individuals with more severe alcohol use problems showed increased discounting of delayed rewards and greater activation in several regions including supplementary motor area, insula/orbitofrontal cortex, inferior frontal gyrus, and the precuneus.

Conclusions: These results suggest that impulsive choice in alcohol dependence is the result of functional anomalies in widely distributed, but interconnected brain regions involved in cognitive and emotional control. Furthermore, our results suggest that the neural mechanisms of impulsive choice in AUD both overlaps with that observed in previous studies, and shows that individuals with AUD recruit additional mechanisms when making intertemporal choices.

Copyright © 2011 by the Research Society on Alcoholism.

Figures

Figure 1

Sample trial in delay discounting task. Participants were given two options, one smaller amount that was available sooner and one larger amount that was more delayed than the more immediate option. When a response was selected, the chosen option was highlighted for 2 seconds, and then a fixation cross was presented for a variable length intertrial interval (ITI).

Figure 2

Correlation between ln(k) and reaction times during the selection of the more immediate response (a) and the larger, more delayed option (b). More impulsive participants, as measured by ln(k), took longer to make a response during the delay discounting task, suggesting that impulsive choice is not necessarily a rash decision.

Figure 3

Main effects of Now vs. Later contrast across all participants. In the Now>Later contrast (blue), impulsive choices activated regions of visual cortex and bilateral PFC. In contrast, selection of the more delayed option (yellow/orange) activated posterior insula, anterior and anterior cingulate cortex, and postcentral gyrus.

Figure 4

Correlation between AUDIT scores and the contrast of Later > Now responses in the delay discounting task. Significant correlations were found in SMA, left insula, right IFG, and cuneus. In all cases, individuals with more severe alcohol problems showed a greater difference between Later and Now trials than individuals with fewer problems.