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Imagine walking through a dark forest at night. Something cracks behind you. Your heart starts racing, your muscles tense and your attention sharpens. You probably do not stop to convene a rational meeting with yourself about the chances of an actual predator lurking behind you. Your body is already reacting before you have had time to think it through.
That is not a flaw in the brain. It is an excellent alarm system.
Fear is useful
Fear helps us respond quickly to threats. A car suddenly hurtling towards you, a snake on the path or the smell of smoke at home: in situations like these, you would rather have a brain that sounds the alarm a little too soon than one that calmly weighs every possibility first.
Fear is also a form of learning. When something turns out to be dangerous, your brain remembers it. That way, you can react faster next time.
One important player is the amygdala, a small region deep inside the brain. It is often called the ‘fear centre’, but that is too simplistic. The amygdala is involved in many processes related to emotional significance, threat and learning. When it comes to fear, it plays an important role in learning to recognise danger. And that is exactly what the Nijmegen study focused on.
Influencing a brain region
The researchers used transcranial ultrasound stimulation, or TUS: sound waves that can reach deep into the brain and temporarily influence the activity of a specific region.
They used TUS to disrupt the amygdala in healthy participants while they learned that an image of a snake could be paired with a mild electrical stimulus.
And sure enough, when the amygdala was stimulated, participants learned the threat association more slowly. Then, when the electrical stimuli stopped appearing alongside the snake images, something interesting happened: they also unlearned the fear response more quickly.
This tells us something important about the amygdala. It does not seem to be a simple switch labelled ‘fear: on’. Instead, it shapes how easily we learn that something is dangerous—and how readily we can revise that information later.
This fits beautifully with fear’s evolutionary purpose. If you encounter a predator and it nearly eats you, it helps to sound the alarm earlier next time. What would not help is deciding five minutes later: oh well, it probably was not that bad.
So where exactly is this off switch?
There is not one.
The researchers did not discover a button-like brain region that we can press to turn fear off. What they did show is that influencing the amygdala can change how we learn and unlearn fear associations.
That is a subtler result, but scientifically far more interesting.
And it could eventually matter for anxiety disorders. In conditions such as PTSD or phobias, the problem is not that fear exists at all. It is that the alarm system keeps reacting long after the danger has passed. Current treatments such as exposure therapy try to correct this by teaching the brain that a situation is safe.
Techniques such as TUS might one day give those learning processes a helpful nudge.
But we are not there yet. This study was conducted in healthy participants and examined the acquisition of new fear responses. Much more research is needed before we know whether and how this approach could be used as a treatment.
The real value of this research, then, lies not in a future off switch for fear, but in an increasingly precise understanding of our own alarm system.
After all, the goal is not a brain that is never afraid. It is a brain that knows when fear is called for—and when the siren has been wailing long enough.
Author: Lucas Geelen
Buddy & Editor: Wieger Scheurer
Translator: Siddharth Chaturvedi
Image by Dima Shishkov on Unsplash
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