Brain’s “Tug of War” Helps Us Balance Risk and Reward

The most valuable decisions we make in life often involve risk. Would you accept a higher-paying job if it meant moving to a new city and starting over? These difficult choices may reflect a neural “tug of war” between rival groups of brain cells.

In research published in Nature Neuroscience on September 15, researchers recorded electrical activity directly from the brains of six people. They identified two adjacent regions in the orbitofrontal cortex (OFC), an area of the brain’s frontal lobe involved in weighing risk and reward.

The researchers found that neurons in one OFC region became more active before participants chose to pursue a reward. Neurons in the other region were more active before participants chose to avoid a risk. During difficult decisions, neural signals rapidly shifted between the two areas before a choice was made.

“What we discovered is that these two brain regions are inversely correlated in real time, meaning that every millisecond, when one is excited, the other is inhibited,” says study co-author Clara Starkweather, a neurosurgery resident at the University of California, San Francisco.

The findings could help researchers better understand risk-taking and avoidance behaviors in conditions including anxiety, obsessive-compulsive disorder, addiction and gambling disorders. “This type of research has the potential to identify brain mechanisms associated with specific symptoms in some psychiatric disorders,” said Pablo Billeque, a neurobiologist at the University of Development of Santiago.

How the brain weighs risk and reward

The orbitofrontal cortex is the “usual suspect in decision-making,” Billeque said. However, it is difficult to study using brain imaging because it lies “right above the eye socket, on a large sheet of bone, on top of the sinuses and eyes,” Starkweather said.

Starkweather and her colleagues worked with six participants who had electrodes surgically implanted in the OFC as part of existing treatments for epilepsy and psychiatric disorders. The researchers designed a video game in which participants moved through hallways lined with treasure chests and bombs. They had six seconds to decide whether to approach or avoid each hallway.

Some choices were straightforward, Starkweather said, such as entering a hallway with seven treasure chests and no bombs. Others created a clear approach-avoidance conflict. Participants had to decide whether to enter or avoid hallways containing an equal number of treasures and bombs, or combinations such as seven treasures and four bombs.

Two brain regions compete before a choice

The results suggest that risk-based decisions are shaped by rapidly changing activity in neighboring areas of the orbitofrontal cortex. One neural population signals the potential value of pursuing a reward, while another signals the need to avoid danger.

The opposing activity may help explain how the brain resolves uncertain choices in real time—and why disruptions in these circuits could contribute to psychiatric disorders linked to risk-taking and avoidance.