How your brain quickly yells ‘Stop!’

Understanding how the brain suddenly cancels a planned action could help identify therapies for Alzheimer's and Parkinson's diseases or ADHD. (Credit: Karen Lee Colangelo/Flickr)

Researchers have found the part of the brain that directs us to make split-second changes in actions—like when a driver slams on the brakes or a batter checks a swing when a pitch suddenly veers out of the strike zone.

Experiments with rats show that neurons in the basal forebrain—a zone that, not surprisingly, lies toward the bottom of the front of our brains—control that response.

“The study discovered a new role for basal forebrain neurons in the control of action,” says Michela Gallagher, professor of psychological and brain sciences at Johns Hopkins University. “This work opens the door to novel approaches focused on this circuit in certain neurological and psychiatric conditions that affect basic cognitive functions of the brain.”

The ability to rapidly stop a behavior is critical for everyday functioning, allowing pedestrians in a crosswalk, for instance, to freeze if a car surprises them and restraining people from grabbing their vibrating phones during a meeting.

Alzheimer’s and ADHD

A better understanding of the cognitive mechanics behind what’s known as reactive inhibition could help people suffering from neurological conditions where such control is diminished—everything from Alzheimer’s disease and Parkinson’s disease to attention deficit hyperactivity disorder and normal aging.

Scientists had assumed the self-control necessary to interrupt and reverse a planned behavior originated in the basal ganglia, a brain area responsible for a variety of motor control functions, including the ability to start an action. Gallagher’s study demonstrates, however, that the “stop” response happens in the nearby basal forebrain, a part of the brain best known for regulating sleep, but also recognized as a site for early neurodegeneration in Alzheimer’s disease.

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The researchers trained rats to play a game: If the rats quickly moved after hearing a tone, they got a treat. The rats were also rewarded if they stopped moving when a light flashed; in that occasional case, the rats had to quickly cancel their planned response and stay still.

All the while, the researchers monitored the rats for electrical signals in the basal forebrain. They were also able to get the rats to stop without flashing a light by stimulating the “stop” neurons with a small pulse of electricity.

“In the lab, we were able to manipulate these neurons, which caused rats to stop their behavior even though they had no reason to do so,” says Jeffrey D. Mayse, lead author of the study published in Nature Neuroscience. Mayse conducted the research as a Johns Hopkins doctoral student and is now a postdoctoral fellow at Brown University.

“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,” he says, “and will be absolutely critical to developing future treatments and therapies for diseases and disorders with impaired reactive inhibition as a symptom.”

The National Institute on Aging and a NARSAD Young Investigator Award funded the study.

Source: Johns Hopkins University