A New Payoff to Risky Decisions

By Shira Polan

Whether it’s putting a bid on a new house or taking an untested shortcut to work, we’re faced with difficult choices every day. In each instance, we must decide between the safe but banal and the risky but potentially rewarding option. Now, scientists have a clearer understanding of how our brains make the tough calls—and make us smarter as a result.

Working with our close relative, the rhesus monkey, researchers at Washington University in St. Louis have identified two areas of the brain that are likely involved in making decisions in uncertain situations. Their new study, published Wednesday, July 27 in the Journal of Neuroscience, sheds light on how the brain processes information about relative risks and benefits to make choices when we’re unsure of the outcome. The new research may also illuminate such disorders as anxiety and gambling addiction, as well as provide new insight into how we learn from past decisions.

“How do we behave under uncertainty?” asks neuroscientist and study author Ilya Monosov. “We think that the brain calculates the best option based on the potential rewards and risks, but we didn’t know how that happens.”

In a previous study, the investigators found that brain cells in a region called the ventral pallidum fire more frequently during decision-making under conditions of uncertainty. The area was already thought by scientists to control reward-seeking behaviors. It’s a part of the limbic system, involved in the regulation of motivation and emotions.

In the new study, Monosov and fellow researchers discovered—to their surprise—that the neurons actually turn off before the animals select a risky option. When a monkey plays it safe, the ventral pallidum cells fire. The finding suggests, Monosov says, that suppressing those cells might result in more risky behavior. He also notes that the ventral pallidum receives dopamine, a powerful chemical that causes us to seek rewards and is thought to play a role in addiction.

A second group of brain cells may also be involved in risky decision-making, the researchers found. Unlike the first group of neurons, which seem to encourage action, cells in an area called the basal forebrain react after a choice is made. During the very pregnant pause between taking action and achieving the hoped-for desirable result, neuron activity in the basal forebrain ramps up. Monosov believes it prepares the brain for learning from the outcome.

When you know exactly what’s going to happen in a situation, there’s little to learn from it. But when you’re uncertain, you need to learn in order to reduce that uncertainty. “That’s one of the major goals of intelligent behavior,” says the St. Louis neuroscientist. “You need to be able to detect uncertainty, act upon it, and then learn from the result. Overall, we think these two distinct mechanisms contribute to decision making: One encourages risky behaviors, the other helps us learn from them.”

That the basal forebrain plays a critical role in learning from past decisions fits with earlier observations of memory impairment. Previous studies have shown that brain region is one of the first to degenerate in Alzheimer's disease.

The new information also offers a fresh perspective on common disorders. “One way of thinking about anxiety and pathological gambling is that they are two sides of the same coin,” Monosov says. “In anxiety, you are risk-averse; in gambling, you prefer it.” Knowing where and how the brain processes uncertainty and reward may help scientists understand, and perhaps even treat, risk-related problems.

Monosov and his team are not done yet. In their next set of studies, they plan to disrupt different parts of both brain regions to test the effects on decision-making and learning. They want to understand how information about uncertainty travels through the brain and affects all behavior.