The role of dopamine in risk taking: a specific look at Parkinson’s disease and gambling

Abstract

An influential model suggests that dopamine signals the difference between predicted and experienced reward. In this way, dopamine can act as a learning signal that can shape behaviors to maximize rewards and avoid punishments. Dopamine is also thought to invigorate reward seeking behavior. Loss of dopamine signaling is the major abnormality in Parkinson’s disease. Dopamine agonists have been implicated in the occurrence of impulse control disorders in Parkinson’s disease patients, the most common being pathological gambling, compulsive sexual behavior, and compulsive buying. Recently, a number of functional imaging studies investigating impulse control disorders in Parkinson’s disease have been published. Here we review this literature, and attempt to place it within a decision-making framework in which potential gains and losses are evaluated to arrive at optimum choices. We also provide a hypothetical but still incomplete model on the effect of dopamine agonist treatment on these value and risk assessments. Two of the main brain structures thought to be involved in computing aspects of reward and loss are the ventral striatum (VStr) and the insula, both dopamine projection sites. Both structures are consistently implicated in functional brain imaging studies of pathological gambling in Parkinson’s disease.

Gambling Disorder in the Context of Parkinson’s Disease

“…These results are compatible with the idea that DA treatment can trigger GD in susceptible people with PD who have a pre-existing defect in set-switching, concept formation, and decision making, functions dependent on intact dopamine circuitry. 6 …”

“…The current estimate is that genes account for 33-57% of the overall variance in the risk of developing pathological gambling behaviour in the context of PD. 6 Dysregulation of the mesocorticolimbic dopamine system is thought to be the major route by which the relevant genes lead to impulse disorders in PD, but there is also evidence for alterations in other neurotransmitter systems.…”

“…Dopamine, serotonin, and norepinephrine genes have been shown to contribute approximately equally to the risk of pathological gambling, but together explaining only 15-21% of the variance. 6,15,16 Dopamine is thought to affect decision-making by specifically modulating the perceived attractiveness of potential choices. 17 In animal experiments, impulsivity has been shown to result from amphetamine-induced release of dopamine in the striatum of the brain.…”

Decisions, Decisions: The Neurobiology of the effects of Dopamine Replacement Therapy on Decision-Making in Parkinson’s Disease

“…Thus, it may be puzzling why Mrs. A, and many others with PD, show poor decision-making, high impulsivity, and impaired reward-processing (Weintraub et al, 2010). Dopamine replacement therapy (DRT) in the form of levodopa and dopamine agonists are largely successful in reducing the motor symptoms seen in PD, by targeting the dramatic degradation of dopamine-producing neurons in the substantia nigra pars compacta (Clark & Dagher, 2014;Ryterska, Jahanshahi, & Osman, 2013). However, any manipulation of dopamine levels in the substantia nigra has knock-on effects for interconnected frontostriatal regions involved in decision-making (Zgaljardic, Borod, Foldi, & Mattis, 2003).…”

Neuronal and Psychological Underpinnings of Pathological Gambling

“…In this Research Topic, Clark and Dagher (2014) provide a review of the literature investigating the relationship between DA agonists and impulse control disorders in Parkinson's patients, and how this relates to potential gains and losses within a decision-making framework. They provide the beginnings of a hypothetical model of how DA agonist treatments affect value and risk assessments.…”