When athletes line up at the start of a race, the crowd often hushes in anticipation until the quiet is broken by the crack of a starter pistol. The discharge sounds like a real gunshot, yet most people aren’t filled with fear. Instead, the race begins, the fans cheer, and the blast is forgotten.
To not react negatively to a starter pistol, the brain has to recognize the blast as harmless and then shut down any fearful reactions. But how does the brain know when to ignore a starter pistol but then react to a real gunshot?
A 2025 study in Science revealed the brain mechanism in which animals are able to overcome such fears. The research could help scientists better understand how to help people with anxiety, phobias, or post-traumatic stress disorder (PTSD).
The Brain and Fear
People are born with innate fears, like reacting to loud noises. These fears can be helpful if there is an actual threat. Otherwise, the brain has to learn when typically scary stimuli are harmless and can be ignored.
“One example is how humans respond to fireworks,” says Sara Mederos, the lead author of the study and a research fellow in the Hofer Lab at Sainsbury Wellcome Centre at University College London.
Babies and little kids often cry on the Fourth of July when they hear fireworks because they are loud, unpredictable, and possibly dangerous.
“However, through repeated exposure and learning, they typically come to understand that these are not harmful and can enjoy them,” Mederos says.
Read More: The Science of a Good Scare
How the Brain Recognizes Fear
So, how does the brain learn to recognize potentially scary stimuli as not a big deal? Mederos and her research team set out to map the neural pathways that allow animals’ brains to turn off a fear response.
In their study, the team worked with mice because their brain structures have similarities with human brains.
And mice don’t have poker faces, which makes it easy for scientists to analyze their behavior.
“Mice are an excellent model for studying instinctive fear because they exhibit well-characterized defensive behaviors in response to visual threats, such as freezing or fleeing,” Mederos says.
One situation in which mice might freeze or flee is when the shadow of an aerial predator appears. In their laboratory, Mederos and her team used an overhead projector to simulate the shadow of a raptor.
At first, the mice responded as expected and ran for cover. “However, through repeated exposures, they learned that the stimulus did not represent a real threat and adapted their responses accordingly, and stopped escaping,” Mederos says.
The researchers then analyzed what happened in the mice's brains when they learned to suppress their fear of the shadows. The results were surprising — visual information plays a role in the learning process, but only to a point.
How to Tame Fear
The researchers found that the higher visual areas of the cerebral cortex were responsible for the learning process that taught the mouse it was okay to not flee from the raptor shadow. But, once the lesson was learned, these visual areas were no longer needed.
The researchers also had another surprise finding when they learned the related memory was stored in the subcortical circuit in the ventrolateral geniculate nucleus (vLGN).
“This was unexpected because plasticity is typically studied in cortical areas like the hippocampus rather than in subcortical regions,” Mederos says. The findings will help scientists better understand how animals process fear, store memories, and learn from past events. The research may also extend to humans one day.
“While the instinctive fear responses we studied are more relevant to animals in the wild, the brain pathway we identified also exists in humans. This suggests that similar mechanisms could be involved in regulating fear and anxiety in people,” Mederos says.
For most people, regulating fear and anxiety simply means getting exposed to the threat multiple times until the brain realizes it’s not worth getting worked up. But for people with anxiety, phobias, or PTSD, Mederos says the process becomes impaired, and they continue to have a reaction to non-threatening stimuli.
“Instead of adapting to non-threatening stimuli, their brain circuits continue to respond as if the stimulus is dangerous,” Mederos says. “For example, in PTSD, a person who has experienced trauma may develop an exaggerated fear response to everyday cues associated with that event. The fear response becomes overgeneralized, even when the stimulus is no longer a threat.”
Therapies that target the vLGN could involve “deep brain stimulation, focused ultrasound, or pharmacological treatments aimed at modulating endocannabinoid signaling” to treat anxiety, phobias, or PTSD, Mederos says.
“By restoring the brain’s ability to regulate fear, these approaches could help individuals with anxiety disorders gradually learn to suppress excessive fear responses and improve their quality of life,” Mederos says.
Read More: The Science of Recreational Fear: Why We Love Horror Movies and Other Spooky Thrills
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