Brain Mechanism Reveals How We Quickly Switch Motor Actions

Scientists at the University of Southern California (USC) have uncovered a previously unseen brain mechanism that allows humans to rapidly shift between motor actions. The study, published in PLOS Computational Biology, reveals that switching from one action to another is not simply an extension of stopping, but rather a distinct cognitive process.

Motor switching plays a critical role in everyday life, whether adjusting a reach to open a door or reacting quickly to avoid obstacles while driving. Until now, it was widely believed that switching actions involved stopping the initial movement before starting a new one. However, the USC team demonstrated that the brain actively suppresses an ongoing action without halting it first, enabling a seamless transition.

Computational modeling and clinical observations

The research team built a computational model to simulate how the brain selects, stops and switches actions based on changing circumstances. Human participants performed reaching and switching tasks while their motor behavior was recorded and compared with the model’s predictions.

To validate the findings further, the team collaborated with researchers at Cedars-Sinai Medical Center and the University of Texas Southwestern Medical Center to observe Parkinson’s disease patients undergoing deep brain stimulation procedures. The patients played simple video games during surgery, allowing researchers to monitor real-time brain activity in motor control regions.

The subthalamic nucleus, a deep brain region sometimes referred to as the brain’s braking system, was a focal point of the study. Overactivity in this area is associated with tremors and slowed movements, common symptoms in Parkinson’s disease.

Implications for clinical treatments and engineering

Understanding the mechanisms behind action switching has important implications for clinical practice. Better knowledge of how Parkinson’s disease disrupts these processes could help improve deep brain stimulation treatments, reducing side effects and enhancing patient outcomes.

“Traditionally, psychologists believe that switching is an extension of stopping. It’s what we call ‘go, stop, go.’ You go. You stop and you switch to the new action. However, we believe that – especially when you have to perform something really fast – your brain doesn’t do that. Instead, the new action suppresses your current action without using another mechanism to inhibit it. Stopping and switching are two different cognitive motor processes.”

Dr. Vasileios Christopoulos.

The research also holds promise for engineering fields. Insights into biologically-inspired decision-making could inform the development of robotic systems capable of rapidly adapting to dynamic environments, similar to human behavior.

The team plans to continue comparing simulated predictions with patient brain activity data, advancing understanding of the neural architecture responsible for rapid decision-making.

Reference: Zhong S, Pouratian N, Christopoulos V. Computational mechanism underlying switching of motor actions. Papin JA, ed. PLoS Comput Biol. 2025;21(2):e1012811. doi: 10.1371/journal.pcbi.1012811

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