Between Acting and Stopping, a Brain Is Unfolding in Time

Perhaps one of our most important possibilities is not initiating a movement, but noticing when there is still time to interrupt it

Imagine the traffic light turns green.

Your foot begins moving toward the accelerator.

Then, suddenly, a child runs across the street.

You need to stop.

Not five seconds from now.

Not after completing the movement that has already begun.

Now.

There is an enormous difference between knowing that we should stop and actually being able to interrupt an action before it is too late.

In 2026, Eunseo Oh, Yang Seok Cho, and Sung-Phil Kim published a study in iScience examining precisely this interval: the brief period between an action being prepared and a process attempting to cancel it.

The researchers studied so-called beta bursts — brief, transient increases in brain activity within the beta frequency range — during a movement cancellation task.

Their main finding was not simply that there was more or less beta activity.

It was something more interesting:

when participants successfully canceled a movement, certain beta bursts appeared earlier than when stopping failed.

Perhaps, then, a question about action control is also a question about time.

And that is exactly where our conversation begins.

A race between doing and stopping

The researchers used a classic paradigm called the stop-signal task.

The logic is simple.

On most trials, participants receive a signal and must respond quickly.

Go.

But on some trials, another signal appears shortly afterward:

Stop.

The movement is already being prepared.

Now it must be canceled.

In the study, 44 participants performed the task while their brain activity was recorded using EEG. Some stopping attempts were successful, while in others the response occurred despite the stop signal.

One common way of understanding this task is to imagine a race.

On one side there is a process:

GO.

On the other:

STOP.

If the stopping process reaches its goal before the action is executed, the movement is canceled.

If it arrives too late, the action happens.

So it is not enough for the organism to possess a mechanism capable of stopping.

It has to enter the race in time.

What beta bursts revealed

Beta bursts are brief episodes of increased activity in the beta frequency range, and previous research has associated them with motor control and response inhibition.

Oh and colleagues asked a more precise question:

does the timing of these bursts distinguish successful stopping from failed stopping?

The answer was yes.

After the stop signal, frontal beta bursts increased earlier on trials in which the movement was successfully canceled.

Analyses using multiple EEG channels and neural trajectories pointed in the same general direction: patterns associated with stopping began to diverge earlier when cancellation succeeded.

The authors also observed a temporal progression involving frontal, then frontocentral, and finally motor regions.

But perhaps one of the most interesting methodological findings was something else.

When researchers simply averaged beta activity across a broad time window, part of the difference disappeared.

The crucial information was in when the bursts occurred.

Traditional measures of average beta amplitude did not capture those temporal differences in the same way.

In other words:

sometimes knowing how much happened is not enough.

We need to know when it happened.

Stopping is also an event

In everyday language, we often think of movement as action.

And stopping as the absence of action.

But perhaps that is too simple.

For a prepared action not to occur, something still has to happen within the organism.

The movement has to be interrupted in time.

This produces an interesting question for BrainLatam:

Can stopping also be considered a movement?

Not necessarily a muscular movement.

But a change in the trajectory of action.

A course of action has begun.

New information appears.

The organism must reorganize what it was about to do.

In that sense, perhaps the opposite of movement is not simply immobility.

There may be a movement capable of preventing another movement.

When can a movement still stop becoming an action?

Here we need to be careful.

Oh and colleagues did not study free will.

They did not study consciousness.

They did not study Zone 2.

And beta bursts are not a neural marker of freedom.

The study concerns motor inhibition within a specific experimental task.

But its findings allow BrainLatam to formulate a new question:

At what point can a movement that has already begun to be prepared still fail to happen and give way to another?

Think of something ordinary.

You reach for your phone almost automatically.

You begin opening a social media app.

Then you notice the movement.

And put the phone away.

Or you are about to respond aggressively.

The sentence has already begun to form.

But something happens before you say it.

You stop.

These examples are far more complex than the task studied by Oh and colleagues.

We cannot equate them directly.

But they share a question:

when can an already initiated trajectory still be changed?

Perhaps freedom also needs time

At BrainLatam, we have been discussing the possibility of perceiving a movement before simply being carried by it.

This brings us close to something fundamental:

time available for perception.

If an organism must respond immediately to everything, perhaps there are fewer opportunities to interrupt movements that have already been prepared.

If there is some space between stimulus and response, perhaps other possibilities can enter the repertoire.

Again: the article does not demonstrate this.

This is a BrainLatam hypothesis that would need to be tested.

But it allows us to ask a powerful experimental question:

Does increasing the time available to perceive an action being prepared increase the possibility of changing it?

And further:

is that effect the same for everyone?

The Latin American question

Now place that body inside a territory.

Imagine crossing a quiet street.

Then imagine crossing a crowded avenue.

Now imagine living in a territory where you must remain constantly alert to the possibility of violence.

A safe classroom.

A classroom where making a mistake means humiliation.

A workplace where there is time to review a decision.

Another where any delay may mean losing income.

The brain remains a brain in all these places.

But the temporal demands imposed on the body are different.

This leads to an important question for Latin America:

How much of a person’s capacity for control also depends on the amount of time their territory allows them to have?

We are not saying that poverty, violence, or inequality produce a specific beta-burst pattern.

Oh and colleagues did not investigate that.

We are asking whether territorial conditions that demand rapid, repetitive, or permanently defensive responses might change the opportunities available for interrupting, reconsidering, or replacing certain actions.

That question can be studied.

We can design better experiments

Imagine comparing the same decision-making task under different conditions.

In one condition, participants must respond immediately.

In another, they receive a few extra seconds before acting.

In a third, they are trained to recognize bodily signals associated with response preparation.

We could use:

EEG, to examine the temporal dynamics of inhibition.

Eye-tracking, to follow attention.

Heart rate and heart-rate variability, to observe physiological state.

Behavioral measures, to identify when a response can still be interrupted.

Then we could increase the complexity.

Athletes.

Drivers.

Healthcare professionals.

Students.

People making financial decisions.

Not to search for a “brain signal of the correct choice.”

But to ask:

What changes the window in which an action can still be reconsidered?

That may be an important contribution neuroscience can make to other fields of knowledge.

And what if our systems also do not know how to stop?

Here we can use a metaphor — and only a metaphor.

States do not have beta bursts.

Institutions do not have frontal cortices.

A public policy does not have an EEG.

But human systems also initiate movements.

We create a rule.

A technology.

An economic policy.

A way of teaching.

A way of organizing a city.

At first, that movement may make sense.

Then the territory changes.

New data appear.

New consequences.

New populations.

New technologies.

And then a similar question emerges:

Is there any mechanism capable of saying, “Stop. We need to reconsider this movement”?

Or do our systems simply continue because they have already begun?

Here the connection to the article is metaphorical, not neurobiological.

But the question matters.

Perhaps intelligence is not only the ability to execute a policy efficiently.

Perhaps it is also the ability to recognize in time when continuing to do the same thing is no longer the best movement.

Where the article ends and BrainLatam begins

Oh, Cho, and Kim showed that successful movement cancellation was associated with earlier engagement of beta bursts, particularly in frontal regions, and that the temporal dynamics of these events distinguished successful from failed stopping more clearly than traditional measures of average beta amplitude.

Up to this point:

Oh and colleagues.

From this point onward:

BrainLatam.

We are not claiming that beta bursts are freedom.

We are not claiming that canceling a simple movement is equivalent to changing a belief, a social decision, or a public policy.

Our question is simpler:

When can a movement still stop becoming an action?

And then:

What increases or reduces the time available for another movement to become possible?

Perhaps this window can be studied.

At the level of the individual.

At the level of the Body-Territory.

And, at another scale and with different tools, perhaps also at the level of society.

Because not every action that has begun necessarily needs to reach its end.

Perhaps one of the most important forms of intelligence is precisely the ability to recognize:

there is still time to do something different.

Neuro Challenge Latam

Think of a decision you made almost automatically today.

At what moment could you still have interrupted it — and what would have needed to happen for another movement to take its place?

Scientific Reference

Oh, E., Cho, Y. S., & Kim, S.-P. (2026). Distinct temporal patterns of beta bursts differentiate successful and failed movement cancellation. iScience, 29(6), 116034. https://doi.org/10.1016/j.isci.2026.116034