A rider’s decision to jump a fence or a gambler’s decision to continue a losing game might be considered risky business. What prompts human beings to take such decisions? Chemical signals in the brain, according to new research from the University of British Columbia, which found that dopamine levels play a key role in how humans perceive a risk and the reward or failure associated with it.

"Our brains are constantly updating how we calculate risk and reward based on previous experiences, keeping an internal score of wins and losses," said Stan Floresco, co-author and professor in UBC's Department of Psychology, in a press release. "Dopamine appears to play an important role in these processes, influencing our everyday choices."

The "feel good" neurotransmitter dopamine controls most of our emotions. Feelings of love, bliss, pleasure, euphoria are all controled by adequate levels of dopamine. While low levels of dopamine lead to feeling of remorse or inadequacy. Recent research has also linked low levels of dopamine to several psychiatric disorders such as schizophrenia, depression, and drug addiction.

The researchers also wanted to see if the neurotransmitter was involved in risk-taking decisions. Previous studies have already shown that dopamine levels increase when risky decisions offer rewards. To further prove this theory, they used rats and subjected them to tests where they had to choose between safe and risky rewards. The rats were kept in enclosures that contained two levers.

Pressing one lever gave the rodents a small, but guaranteed reward while the other lever yielded a large reward or nothing. The researchers likened this scenario to a Wall Street investor’s dilemma where a bond offers a guaranteed, small reward, while a high-risk stock a risky but unknown reward.

The researchers also altered the rats’ decision-making process by shutting down or turning on the dopamine signals in their brains. When rats chose the risky reward and did not get anything, the researchers turned on dopamine signals when normally they would have decreased. As a result of elevated levels of dopamine, rats made riskier decisions. Conversely, when the rats won after a risky decision, researchers turned dopamine signals off, after which the rats began to play more cautiously.

"By temporarily knocking these chemical signals out, it demonstrates how significant they are in altering our decisions, even if it's against our better judgment," Floresco said.

While the aim of this experiment to show the involvement of dopamine in risk-taking decisions has been proved, its potential clinical application still needs to be worked on. This means the effect of altering dopamine levels for targeted therapy in psychiatric disorders immediately following a risk or reward decision needs to be evaluated.

"The timing of the stimulation is important," Floresco said. "By understanding how these signals work to influence our behaviour, these findings can provide insight into what happens when these signals go awry, as may occur in numerous psychiatric disorders."

Source: Floresco S, Stopper C, Tse M, Montes D, Wiedman C. Overriding Phasic Dopamine Signals Redirects Action Selection during Risk/Reward Decision Making. Neuron. 2014.