The Brain's Tug-of-War Between Impulse and Self-Control

Resisting an impulse can feel like a battle between what we want to do and what we know we should do. Researchers at The University of Texas at Austin have uncovered new clues about how the brain regains control when those urges threaten to take over. The findings could help scientists better understand why people struggle to resist urges in conditions such as addiction and obsessive-compulsive disorder and eventually guide the development of neuroprosthetic devices designed to help people better control those urges.

“A big focus of my lab is trying to understand compulsive behavior on the biological level — to figure out why it’s so difficult for us to ignore things in our environment that tempt us,” said Thomas Elston, an assistant professor in the Department of Neuroscience and Center for Perceptual Systems at UT, who led the work. “This research was remarkable because for the first time, we could directly observe how the brain detects the need for self-control and deploys it to interrupt automatic behaviors.”

The study, published this month in Neuron, focused on how two brain areas implicated in compulsive and addictive behaviors, the orbitofrontal cortex (OFC) and striatum, interact. The striatum is known to coordinate automatic, unconscious behaviors — the brain’s autopilot system. The OFC is known to guide conscious decisions based on maximizing reward. Abnormal interactions between the OFC and striatum are connected to addictive and compulsive disorders. However, exactly how these areas interact to override automatic behaviors remained unclear.

To find out, Elston trained two non-human primates to play a computer game where they chose between options that paid different amounts of reward — drops of apple juice. The catch was that the best option in one scenario was the worst in another. This often led the monkeys to make an initial response based on a reward associated with a different context. Sometimes they caught themselves and corrected their mistake, and sometimes they didn’t. Critically, these automatic-then-controlled responses occurred despite the monkeys having full knowledge of what the context was and how to respond. In other words, the task elicited a form of automatic behavior that could override a conscious goal. By inserting electrodes into the OFC and striatum as the monkeys performed the task, Elston could directly observe how the brain overrides automatic responses, and what happens when it does not.

Prior to this research, scientists believed the brain stopped automatic behaviors by dialing down activity in the striatum, like turning down a thermostat. Surprisingly, Elston found that the total amount of neuronal activity in the striatum was the same regardless of whether the automatic response was inhibited or not. Instead, he found that the OFC “jammed” the striatum, disrupting the organized brain signals that drive automatic behaviors. This is like speaking with someone who suddenly switches to a language you don't understand. They're still talking, but the message is lost.

“I was very surprised,” Elston said. “The way that the executive control center overrides our habit center is a completely different mechanism than what we expected.” 

In related research, Elston and his colleagues are studying these connections in people, recruiting participants to play the same computer games as his non-human primates while also conducting internet-based psychiatric evaluations. This allows the team to study the same mental processes in humans and non-human primates and better understand the biology behind them. While still at an early stage, his team has already found evidence that failures of self-control in this behavioral task can predict the severity of addictive and compulsive symptoms in people. 

“Ultimately, my goal is to develop a ‘reverse-translational pipeline’ — where we use humans to determine what we should study in animals. Then, we take those insights into the hospital. By using the exact same behavioral tasks in humans and non-human primates, we ensure that our animal work is directly relevant to advancing human health.”

This work was supported by the National Institute of Mental Health, part of the National Institutes of Health. The co-author of the study is Joni Wallis at the University of California, Berkeley. Elston collected data at UC Berkeley while he was a postdoctoral fellow and analyzed it after starting his lab at UT Austin.

This research was reviewed and approved by the Institutional Animal Care and Use Committee at UC Berkeley, as regulated by the U.S. Department of Agriculture and National Institutes of Health Guidelines.