Image Courtesy of Flickr.
Have you ever wondered what causes that queasy feeling that others might be out to get you? Researchers call this feeling paranoia, and it is believed to stem from one’s inability to adapt to new situations. Paranoia is associated with disruptions in volatility beliefs—our expectations of change. A study led by Praveen Suthaharan, a graduate student in Yale’s Interdepartmental Neuroscience Program, sought to identify the brain regions responsible for volatility beliefs.
His team explored two contenders: the orbitofrontal cortex (OFC), linked to adaptive behavior, and the magnocellular mediodorsal thalamus (MDmc), which is associated with reward learning. Monkeys with lesions of either the OFC or the MDmc were presented with three options on a screen, with one choice yielding a reward for the fewest clicks. The catch: the reward probability per choice eventually reversed—a task called a probabilistic reversal learning task. Computational modeling was used to relate the monkeys’ behavior to human decision-making patterns.
The MDmc-lesioned monkeys demonstrated heightened volatility beliefs and switched choices after selecting the “winning” choice. In contrast, OFC-lesioned monkeys continuously clicked the least-rewarding choice, indicating decreased reward learning. The researchers implicated the mediodorsal thalamus in causing human paranoia based on the volatility impairments displayed. “I’m excited about how this cross-species approach helps us understand the link between the brain’s biology and the mind’s experience. It’s a crucial step toward improving our understanding of psychiatric conditions and will guide future mental health research,” Suthaharan said. The next time you look over your shoulder with apprehension, ask yourself if someone is truly there, or if your unsubstantiated volatility beliefs are to blame.