Increasing dopamine levels in healthy adults often leads people to choose more risky options, according to new research published in The Journal of Neuroscience. The findings shed new light on the role that dopamine plays on emotion and decision-making.
The neurotransmitter dopamine is involved in reward learning, and prior studies have linked dopamine drugs such as L-DOPA with compulsive gambling problems in people with Parkinson’s disease.
The current study, led by Robb Rutledge at University College London, shows that boosting dopamine levels in healthy adults led participants to take greater risks in gambling tasks and to feel just as happy with small rewards as they do with large ones, compared to those on placebo.
For the study, 30 healthy adults performed a gambling task on two separate occasions, once after receiving L-DOPA and once after receiving a placebo. The experiment required participants to choose between safe and risky options that led to money gains and losses.
Sometimes, the subjects could choose between a small reward or a gamble where there were equal chances of winning a larger reward or getting nothing. Other times, subjects could accept a small loss or choose a gamble where there were equal chances of losing a larger amount or losing nothing. During the testing, subjects were repeatedly asked, “How happy are you at this moment?”
According to the findings, participants took more risks to try to win bigger rewards after receiving L-DOPA but not when they took placebo. However, L-DOPA did not affect how often subjects took risks when there were potential losses.
Also, after receiving L-DOPA, participants chose more risky options regardless of how much larger the potential reward was compared to the safe alternative.
Furthermore, participants were happier after winning a small reward while on L-DOPA than they were winning the same reward while on a placebo. On a placebo, happiness levels were greater after winning large rewards compared to small rewards, but on L-DOPA, participants were just as happy about small rewards as they were about large rewards.
Based on the findings, the researchers propose that L-DOPA made potential rewards seem more appealing but did not affect a person’s perception of potential losses. They also speculate that, while on L-DOPA, participants might experience similar dopamine release for all reward levels, which would explain why they were equally happy with both small and large rewards.
This study gives us a better understanding of dopamine’s effects on decision-making and emotion, said Nathaniel Daw, a neuroscientist at New York University who was not involved in the study. The results “may help to explain some kinds of gambling and impulse control problems, and also aspects of mood disorders.”
Source: Society for Neuroscience