For the first time in humans, researchers have identified the neurons responsible for canceling planned behaviors or actions, a highly adaptive ability that, when lost, can lead to unwanted movements. Known as stop-signal neurons, they are instrumental in prompting someone to stop or abort an action they have already taken. For example, we’ve all had the experience of sitting at a traffic light and starting to step on the accelerator pedal, but then realizing the light is still red and quickly pressing the brake again.
The study results reveal that such neurons exist in an area of the brain called the subthalamic nucleus, which is a routine target for treating Parkinson’s disease with deep brain stimulation. Patients with Parkinson’s disease simultaneously suffer from both the inability to move and the inability to control excessive movement. This combination of symptoms has long been attributed to impaired function in brain regions that regulate starting and stopping movement. Despite years of intense research, it has been difficult to define how this process occurs and which brain regions are responsible.
This study helps to understand how the human brain is wired to perform rapid movements. To reach their discovery, they studied patients with Parkinson’s disease who were undergoing brain surgery to implant a deep brain stimulator, a relatively common procedure to treat the condition. Electrodes were inserted into the basal ganglia, the part of the brain responsible for motor control, to precisely aim the device while the patients were awake.
The researchers discovered that neurons in one part of the basal ganglia region, the subthalamic nucleus, indicate the need to stop an action already started. These neurons responded rapidly after the appearance of the stop signal.
This discovery provides the ability to more precisely target deep brain stimulation electrodes, thereby targeting motor function and bypassing stop signal neurons.