Dopamine Modulation of Intertemporal Decision-making: Evidence from Parkinson Disease

Abstract

Abstract■ Choosing between sooner smaller rewards and larger later rewards is a common choice problem, and studies widely agree that frontostriatal circuits heavily innervated by dopamine are centrally involved. Understanding how dopamine modulates intertemporal choice has important implications for neurobiological models and for understanding the mechanisms underlying maladaptive decision-making. However, the specific role of dopamine in intertemporal decisions is not well understood. Dopamine may play a role in multiple aspects of intertemporal choices-the valuation of choice outcomes and sensitivity to reward delays. To assess the role of dopamine in intertemporal decisions, we tested Parkinson's disease patients who suffer from dopamine depletion in the striatum, in either high (on medication, PD ON ) or low (off medication, PD OFF ) dopaminergic states. Compared with both PD OFF and healthy controls, PD ON made more farsighted choices and reduced their valuations less as a function of increasing time to reward. Furthermore, reduced discounting in the high dopaminergic state was robust across multiple measures, providing new evidence for dopamine's role in making decisions about the future. ■

Willing to wait: Elevated reward-processing EEG activity associated with a greater preference for larger-but-delayed rewards

“…Here using EEG, we were able to separate reward-processing neural activity at each temporal stage into different indices based on time and frequency dimensions. In line with recent research (Benningfield et al, 2014; Boettiger et al, 2007; Foerde et al, 2016), we found that a stronger preference toward larger-but-delayed rewards was associated with enhanced reward-related neural activity at specific stages of reward-processing. Our findings not only substantiates the association between individual differences in delay-discounting responses and reward-processing, but also provides specific details about which stages of reward-processing are driving these associations.…”

“…Additionally, individuals with the Met-allele of the COMT-gene, which has been associated with elevated reward-related brain function (Chen et al, 2004; Yacubian et al, 2007), show a preference for larger-but-delayed reward (Boettiger et al, 2007; Gianotti et al, 2012; Smith & Boettiger, 2012; Yacubian et al, 2007). Similarly, a recent study also found a stronger preference toward larger-but-delayed rewards as a result of medications designed to increase dopamine signaling in patients with Parkinson’s disease (Foerde et al, 2016). Thus, combined with results from the present study, we argue that there is growing evidence that elevated reward-processing is associated with a higher propensity to forgo smaller-but-immediate rewards, in favor of larger-but-delayed rewards.…”

“…Critically, Met-allele carriers also show a preference toward larger-but-delayed rewards (Boettiger et al, 2007; Gianotti, Figner, Ebstein, & Knoch, 2012; Smith & Boettiger, 2012). More recently, research with Parkinson patients suggests that medications designed to elevate dopamine signaling are associated with a heightened preference for larger-but-delayed rewards (Foerde et al, 2016). Thus, taken as a whole, evidence from fMRI, animal, genetic, and pharmacological studies suggest that individuals with elevated reward-processing have a tendency to wait for larger rewards and forgo smaller-but-immediate rewards.…”

“…2 Drawing on existing research (Benningfield et al, 2014; Boettiger et al, 2007; Foerde et al, 2016), we predict that enhanced reward-related neural activity will be associated with a greater preference for larger-but-delayed rewards. An important contribution of this study is that we examined the relationship between reward-related neural activity and delay discounting tendencies at different temporal stages of reward-processing based on EEG time-frequency characteristics.…”

Steeper discounting of delayed rewards in schizophrenia but not first-degree relatives

“…It is possible that compensatory processes in family members obscure underlying genetic vulnerabilities, but the simplest interpretation is that higher discounting in schizophrenia is associated with the illness itself, or its treatment. Drugs that enhance dopamine signaling decrease discounting (de Wit et al, 2002; Foerde et al, 2016). Antipsychotics generally block dopamine (D2) receptors, and decreased D2 receptor availability is associated with increased discounting (Ballard et al, 2015).…”