Dopamine Increases a Value-Independent Gambling Propensity.

Francesco Rigoli,Peter Dayan,Raymond J Dolan,Benjamin Chew,Olga T Ousdal,Robb B Rutledge

doi:10.1038/npp.2016.68

Abstract

Although the impact of dopamine on reward learning is well documented, its influence on other aspects of behavior remains the subject of much ongoing work. Dopaminergic drugs are known to increase risk-taking behavior, but the underlying mechanisms for this effect are not clear. We probed dopamine's role by examining the effect of its precursor L-DOPA on the choices of healthy human participants in an experimental paradigm that allowed particular components of risk to be distinguished. We show that choice behavior depended on a baseline (ie, value-independent) gambling propensity, a gambling preference scaling with the amount/variance, and a value normalization factor. Boosting dopamine levels specifically increased just the value-independent baseline gambling propensity, leaving the other components unaffected. Our results indicate that the influence of dopamine on choice behavior involves a specific modulation of the attractiveness of risky options—a finding with implications for understanding a range of reward-related psychopathologies including addiction.

Highlights

Dopamine has a fundamental role in adaptive behavior, having a well-established influence on reward learning
We found no difference in gambling percentage between low- and high-value contexts (S1: t(31) = − 0.306, p = 0.762; S2: t(31) = − 0.891, p = 0.380; S3: t(31) = − 0.968, p = 0.341) even when considering gambles for expected value (EV) that overlapped in the two contexts (S1: t(31) = 0.127, p = 0.900; S2: t(31) = − 0.574, p = 0.570; S3: t(31) = − 0.403, p = 0.689)
A final prediction we considered is that boosting dopamine levels would imply that all rewards would appear subjectively less or more valuable, resulting in changes of average gambling in participants with convex and concave subjective value functions

Summary

INTRODUCTION

Dopamine has a fundamental role in adaptive behavior, having a well-established influence on reward learning. Other evidence indicates that dopamine impacts ongoing behavior in a way that is orthogonal to learning, something that speaks to a broader range of functions (Berridge, 2007; Zhang et al, 2009) that are subject of much recent work (Palmiter, 2008; Rigoli et al, 2016a; Sharot, et al, 2009a; Pine et al, 2010; Jocham et al, 2011; Guitart-Masip et al, 2012; Shiner et al, 2012; Wunderlich et al, 2012; Norbury et al, 2013). We analyzed participants’ choice behavior in a gambling paradigm (Rigoli et al, 2016b) where, crucially, several components of risk preference could be disentangled: a baseline risk propensity, a risk propensity dependent on amount/variance, a normalization factor, and an index of choice precision

Participants

RESULTS

DISCUSSION