Summary: Can we “unlearn” fear using sound? Neuroscientists demonstrated for the first time that targeted ultrasonic waves can help the human brain overcome fearful memories more quickly.
By directing high-frequency, inaudible vibrations at the amygdala—the brain’s emotional command center—researchers were able to slow down the formation of new fears and, more importantly, accelerate the process of “unlearning” them. This non-invasive technology offers a potential breakthrough for treating PTSD and anxiety disorders without surgery or drugs.
Key Facts
- Targeting the Amygdala: The study used a small, wearable device to send ultrasound waves deep into the almond-shaped amygdala, which regulates how strongly emotional experiences are stored.
- Slower Fear Learning: Participants stimulated with ultrasound were slower to develop a fear response to “threatening” images (snakes paired with mild shocks) compared to those without stimulation.
- Faster “Unlearning”: The most significant result occurred after the shocks stopped. Participants who had received ultrasound previously “unlearned” their fear much faster, even after the device was turned off.
- The “Memory Update” Hypothesis: The findings suggest that fearful memories formed while the amygdala is dampened are less “sticky” and easier to modify later, making them less resistant to change.
Source: Radboud University
Neuroscientist Sjoerd Meijer of the Donders Institute at Radboud University has shown for the first time that targeted ultrasonic sound waves can help the brain overcome fear more quickly.
These findings may open new avenues for the treatment of anxiety and trauma-related disorders.
Meijer used a relatively new research method, placing a small device that emits sound waves on the heads of test subjects. These high-frequency vibrations are inaudible to the human ear but can reach and influence very specific areas of the brain. The technology is similar to the ultrasound used to view babies in the womb, but is now being applied to safely support the brain from the outside, without the need for surgery, in unlearning fear.
Amygdala
Meijer directed the sound waves at the amygdala, a small almond-shaped structure deep within the brain that determines how strongly emotional experiences are stored. ‘We know from animal research that the amygdala plays a major role in fear, and brain scans show that this area becomes active when people experience fear. However, it had never been demonstrated in humans that the amygdala is actually crucial for both learning and unlearning fear.’
In the experiment, participants were shown images of snakes. Some of these images were occasionally followed by a mild electric shock, teaching participants which snakes were ‘dangerous’. The researchers measured the intensity of the fear response through sweat reactions on the skin. For half of the images, the amygdala was simultaneously stimulated with sound waves; for the other half, it was not.
‘We found that participants developed a fear response more slowly when the amygdala was stimulated. They required more repetitions to learn to perceive the snakes as threatening, although they did eventually learn.’
Quick to learn, slow to forget
The most striking finding came afterwards. When the “dangerous” snakes were no longer followed by electric shocks, the fear response diminished more quickly in participants whose amygdala had previously been stimulated – even though the ultrasound stimulation had already stopped.
‘This suggests that the amygdala not only determines how quickly we learn fear, but also how easily we can unlearn it. Fearful memories formed when the amygdala is fully active may therefore be more resistant to change, even when the threat has long passed’, says Meijer.
Exposure therapy
These findings open up new therapeutic possibilities. ‘This method could become a valuable addition to exposure therapy for anxiety disorders. In this approach, patients are gradually exposed to what they fear. When a fear memory is reactivated, we could stimulate the amygdala, potentially helping to update that memory more quickly.
We have now demonstrated this effect in the formation of new fear responses; the next step is to investigate whether it also works in modifying existing fear memories.’
Key Questions Answered:
A: Not exactly. It’s more like lowering the volume on the emotional intensity of a memory. The participants still remembered which images were “dangerous,” but their physical body (measured by skin sweat) stopped reacting to them much sooner. It helps the brain realize a threat is gone faster than it normally would.
A: Yes. This technology is very similar to the ultrasound used for pregnancy scans. It is non-invasive, requires no surgery, and doesn’t cause pain. The “vibrations” are so high-frequency that you can’t even hear or feel them while they are working.
A: The goal is to use this during exposure therapy. Currently, patients face their fears gradually, but the “fear memory” can be very stubborn. By stimulating the amygdala during therapy, doctors might be able to “unlock” that memory and update it with the knowledge that the patient is now safe, making the therapy much more effective.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this neurotech and PTSD research news
Author: Lieneke van Dijk
Source: Radboud University
Contact: Lieneke van Dijk – Radboud University
Image: The image is credited to Neuroscience News
Original Research: Open access.
“The human amygdala in threat learning and extinction” by Sjoerd Meijer, Eleonora Carpino, Benjamin R. Kop, Jesse Lam, Lycia D. de Voogd, Karin Roelofs, and Lennart Verhagen. Science Advances
DOI:10.1126/sciadv.aea8233
Abstract
The human amygdala in threat learning and extinction
Here, we resolve the long-standing but unconfirmed hypothesis that the human amygdala is essential for rapidly acquiring cued-conditioned threat responses. We provide causal evidence for the amygdala’s contribution to forming threat memories that are resistant to extinction.
Using transcranial ultrasound stimulation (TUS), a noninvasive technique that modulates deep brain structures with high spatial and temporal precision, we targeted the bilateral amygdala during Pavlovian threat conditioning in healthy adults.
Linear mixed-effects models and computational modeling of trial-level skin conductance responses revealed that amygdala-TUS (experiment I, n = 25), but not hippocampus-TUS (experiment II, n = 25), selectively slowed initial threat acquisition, augmented subsequent extinction, and modulated declarative memory of retrospective threat probability.
These findings demonstrate that the human amygdala drives an emotional learning state—learning fast, forgetting slow.
Our study shows the potential of TUS for targeted neuromodulation of human deep brain structures implicated in conditions such as posttraumatic stress disorder, where pathological threat memories persist despite therapy.
