Neural Tug-of-War Reveals How the Brain Resolves Risk and Reward

When individuals face difficult choices involving both potential gain and loss, their brains engage in a rapid, millisecond-by-millisecond competition between rival neuronal groups. A study published in Nature Neuroscience on 15 September details how researchers observed this internal conflict directly within the human brain.

The investigation focused on the orbitofrontal cortex (OFC), a region located above the eye socket that plays a critical role in balancing risk and reward. Because the OFC sits behind bone and sinuses, it has historically been difficult to analyze using standard brain-imaging techniques. To overcome this, scientists recorded electrical activity from six participants who had electrodes surgically implanted in this area as part of existing treatments for epilepsy or psychiatric disorders.

During the experiment, participants played a video game requiring them to navigate corridors lined with either treasure chests or bombs. They were given six seconds to decide whether to approach or avoid each hallway. While some scenarios were straightforward, such as paths containing only rewards, others presented an approach-avoidance conflict, forcing participants to weigh mixed outcomes like seven treasures against four bombs.

The data revealed two neighboring areas within the OFC that operate in opposition. Neurons in one area showed heightened activity just before a participant chose to pursue a reward, while neurons in the other area became more active prior to a decision to avoid risk. During especially challenging decisions, electrical signals flickered rapidly between these two regions before ultimately settling on a choice.

“What we found was that these two brain regions are anti-correlated in real time. So, millisecond by millisecond, when one is excited, the other is suppressed,” said Clara Starkweather, a neurosurgery resident at the University of California, San Francisco, and co-author of the study.

These findings provide a clearer window into the biological mechanisms underlying risk-taking and avoidant behaviors. Experts suggest this research could help illuminate the neural basis of conditions such as anxiety, obsessive-compulsive disorder, addiction, and gambling disorders.

Pablo Billeke, a neurobiologist at the University of Development in Santiago, noted that understanding these specific brain mechanisms can help isolate the roots of certain symptoms in psychiatric patients. “This kind of research can isolate some brain mechanisms that are related to specific symptoms,” he said.