Johns Hopkins Brain Maps Show Why It Can Be So Hard to Stop
Neuroscientists map three brain areas that work together to stop body movements.
Posted Dec 07, 2017
A potentially game-changing Johns Hopkins University paper, “Neural Basis of Cognitive Control Over Movement Inhibition: Human fMRI and Primate Electrophysiology Evidence,” was published online today in the journal Neuron. As the brain map above illustrates, the neuroscientists identified three key brain areas that are involved in quickly stopping a physical movement that must be nixed for whatever reason.
Everybody knows that discombobulated and spastic feeling of abruptly needing to interrupt a pre-planned physical movement. The urgent need to inhibit body movements happens regularly in the kitchen, on the sports playing field, while driving, when addicts in recovery are compelled by an unstoppable craving to pursue a drug fix, and in countless other situations.
Two kitchen-related examples of needing to halt an action you've already started include the moment you realize that you’re pouring orange juice onto your cereal or when you accidentally grab a sizzling-hot frying pan with your bare hand because you thought it was cool. Doesn't it always seem to take much longer than you'd expect to actually let it go?
In the milliseconds after you become cognizant that you must "red light" something, you’ve already given your body the "green light" to do, most of us have a knee-jerk reaction to blurt out an expletive. (Like most parents, the only time I tend to drop the F-bomb in front of my 10-year-old is when something out-of-the-blue catches me off guard.) As your mind and body scramble to coordinate a new plan of action, your brain is hustling behind the scenes to re-choreograph your next move.
But what exactly is going on inside the brain when someone needs to unexpectedly stop or change a physical movement in the heat of the moment? As mentioned at the outset, a team of Johns Hopkins neuroscientists led by Kitty Z. Xu was curious to answer this question and designed an elegant study involving both human and non-human primates to do so.
While this study was still under embargo, I reached out to lead author Kitty Xu and senior author Susan Courtney, a professor of psychological and brain sciences at Johns Hopkins, to get the inside scoop on what they'd discovered.
My curiosity was piqued by a press release about a forthcoming Johns Hopkins study that mapped the neural basis for movement inhibition. This topic has long been of interest to me as an athlete and coach. (For some background, check out the January 2014 Stanford University paper also published in Neuron that inspired my Psychology Today blog post, "Ready, Set, Go! How Does the Brain Prepare for Movements?")
Xu et al. found that stopping a planned movement requires extremely nimble and swift choreography between several distinct areas of the brain. For example, if you change your mind about taking a step off the curb after noticing there is an oncoming bus...if too many milliseconds have passed since the original "go" message was sent to your muscles, it will be practically impossible to stop yourself from stepping off the curb.
Historically, neuroscientists believed that only one brain region was activated when someone suddenly decided to change his or her movements. But the Johns Hopkins researchers found that in addition to the lightning-fast responses between two brain areas in the prefrontal cortex, there is a third brain area in the pre-motor cortex that helps someone stop, reverse or otherwise change a voluntary movement that is already in progress. When these brain areas don't properly communicate or don't interact fast enough, is when we run into trouble, according to Susan Courtney.
"We have to process all of these pieces of information quickly," Courtney said in a statement. "The question is: When we do succeed, how do we do that? What needs to happen in order for us to stop in time?" The researchers found that the key to being able to stop something we’ve started is all about timing.
Using an automobile analogy: Imagine that you're driving a car. As you approach an intersection, the traffic light unexpectedly turns yellow. Instead of yielding, you decide to step on the gas and zoom through the intersection. But, a few milliseconds after your pre-motor cortex sends the decision to press down on the gas pedal to the part of the brain that will move your foot, you notice a police car parked in the shadows and change your mind.
"Which plan is going to win?" first author Kitty Xu, a former Johns Hopkins graduate student who is now a researcher at Pinterest, said in a statement. "The sooner you see the police car after deciding to go through the light, the better your chance of being able to move your foot to the brake instead. If you're already executing the plan when you see the police car, you're going to go through the light."
Xu and collaborators found that if you attempt to change your mind after 100 milliseconds or less, the odds are that you can do it. However, If it takes you 200 milliseconds or more (which is less than a quarter of a second) you're most likely going to follow through with your pre-planned movement. This is because the original signal is already on its way to the muscles and, by then, you're past the point of no return.
Interestingly, in addition to the three brain areas that work in concert to inhibit movements in the spur of the moment, there appears to be a fourth brain area that continues to process the movement you would have made if you hadn't been able to stop yourself. This region also helps to explain why we can't always stop what we've started. Courtney jokingly refers to this as the "oops" brain area.
The quirky notion of having an "oops" brain area intrigued me. So, in an email to Xu and Courtney, I asked them for more details about the "oops" area to share with Psychology Today readers. In her email response, Xu said: "Based on our finding, there are a few neurons in rVLPFC that would be responsive when you made a mistake (failed to stop). Another finding we didn't particularly emphasize, but could be related to the 'oops' area is we found in the fMRI data that subcortical brain area, subthalamic nucleus (STN), was 'responsive' (not 'responsible') when you failed to stop.”
This research project was supported by both the National Institute on Drug Abuse and the National Institute of Neurological Disorders and Stroke. Clearly, gaining a better understanding of the neural basis of cognitive control over movement inhibition could greatly benefit the target demographic for each of these institutes.
As Susan Courtney explains, “Knowing more about how the brain can stop an intended activity could also be revealing for those dealing with addictions. We think there are similar processes in 'should I do this' and 'can I turn off that thought about the drink,' The sooner I can turn off the plan to drink, the less likely I'll carry out the plan. It's very relevant."
The authors sum up their research by stating: "In conclusion, our findings indicate multiple brain areas involved in multiple complex and task-dependent circuits, all of which contribute to context-dependent and stimulus-selective control of behavior. Within this complex network, the role of VLPFC (ventrolateral prefrontal cortex) seems to be the encoding of context-specific task rules and the detection or monitoring of the need for response inhibition, but not its initiation or instantiation.”
Tragically, Steven Yantis, a beloved professor of psychological and brain sciences at Johns Hopkins, who was a co-author of this study, died in 2014. In memoriam, Susan Courtney said: "Steve Yantis was the bedrock of the department, at once gentle and strong. He was always the voice of reason in any debate because he knew how to identify the most important elements, in a scientific data set, in a faculty candidate, or in life."
Lastly, huge thanks to Jill Rosen, Senior Media Representative in the Office of Media Relations at JHU, for swiftly expediting my inquiry and for your thoughtful follow-up.
Xu, Kitty Z., Brian A. Anderson, Erik E. Emeric, Anthony W. Sali, Veit Stuphorn, Steven Yantis, and Susan M. Courtney. "Neural Basis of Cognitive Control Over Movement Inhibition: Human fMRI and Primate Electrophysiology Evidence." Neuron (Published online: December 7, 2017 ) DOI:10.1016/j.neuron.2017.11.010
Ames, K. Cora, Stephen I. Ryu, and Krishna V. Shenoy. "Neural Dynamics of Reaching Following Incorrect or Absent Motor Preparation." Neuron (Published: January 22, 2014) DOI: 10.1016/j.neuron.2013.11.003