The human brain is a magnificent thing. It enables us to walk, talk, and develop complex longterm plans–as well as make split-second decisions. A group of researchers at Johns Hopkins has been studying those split-second decisions, trying to pinpoint just where in the brain they take place. And according to a new paper, they’ve managed to figure out exactly which neurons are involved when a person slams on the brakes to avoid an accident.

Such actions are known as reactive inhibition–essentially, it’s when you make a split-second decision to stop doing what you were doing (crossing the street, reaching for your phone to check your email). This cognitive mechanism is dampened by diseases such as Alzheimer’s and ADHD; a better understanding just how the brain slams the brakes on a planned action could have wider implications for treating such conditions.

The Hopkins neuroscientists were able to pinpoint the neurons in question by training rats to perform various behaviors and then get rewarded by a treat. According to the Hopkins Hub,

The researchers trained rats to move quickly to get a treat. After hearing a tone, the rats would rush into a new port to lick sucrose water. But, when the tone was followed by a flash of light, the rats would have to immediately stay in place to get a treat. In other words, when the light flashed, the rule of reward reversed—instead of moving quickly to get reward, the rats had to cancel that planned response and stay still to get their treat.

In other words, the rats had to exert split-second self control. By monitoring the animals’ brains, the researchers were able to pinpoint neurons in the basal forebrain as the ones responsible for controlling behavior.

“Understanding how these cells are involved in this form of self-control expands our knowledge of the normal brain circuits involved in everyday decision-making and will be absolutely critical to developing future treatments and therapies for diseases and disorders with impaired reactive inhibition as a symptom,” said Jeffrey D. Mayse, the study’s lead author.