Summary: Can sound be used to weaken fear? Neuroscientists have shown that targeted ultrasonic stimulation of the amygdala can reduce how strongly fearful memories form and can speed up the process of unlearning fear in humans.
Using inaudible, high-frequency ultrasound focused on the amygdala—the brain’s emotion center—researchers slowed the initial acquisition of fear responses and, importantly, found that those fear responses extinguished more quickly afterward. This non-invasive approach could offer a new avenue for treating anxiety disorders and post-traumatic stress disorder (PTSD) without drugs or surgery.
Key Facts
- Targeting the amygdala: A small, wearable transcranial ultrasound device delivered focused ultrasonic waves to the deep, almond-shaped amygdala, which plays a key role in storing emotional memories.
- Slower fear learning: Participants who received amygdala-targeted ultrasound developed conditioned fear responses more slowly than those who did not receive stimulation.
- Faster extinction: After the aversive stimulus stopped, participants previously exposed to ultrasound showed a faster reduction in physiological fear responses, even when stimulation had ceased.
- Memory update hypothesis: The data suggest that when the amygdala is dampened during fear formation, the resulting memories are less resistant to change and are easier to update later.
Source: Radboud University
Neuroscientist Sjoerd Meijer and colleagues at the Donders Institute, Radboud University, demonstrated for the first time in humans that targeted transcranial ultrasound can influence fear learning and extinction.
These results could inform new therapeutic tools for anxiety and trauma-related disorders by enhancing existing behavioral treatments such as exposure therapy.
The researchers placed a compact ultrasound-emitting device on participants’ heads while they underwent a Pavlovian threat-conditioning task. The ultrasound produced high-frequency vibrations that cannot be heard and do not require surgery. This technique is related to medical ultrasound but is adapted to modulate deep brain activity non-invasively and with spatial precision.
Amygdala
The study focused stimulation on the amygdala, a small, deep structure that strongly influences how emotional experiences are encoded and retained. Prior animal work and neuroimaging in humans implicated the amygdala in fear processing, but this study provides causal evidence that modulating amygdala activity affects both the acquisition and the extinction of conditioned fear.
During the experiment, participants viewed images of snakes. Some images were paired occasionally with a mild electric shock to create a learned association between particular images and threat. Researchers recorded skin conductance responses (sweat-related changes in skin electrical activity) to measure the physiological fear response. For half of the conditioned trials, the amygdala received ultrasound stimulation; for the other half, it did not.
Participants exposed to amygdala ultrasound needed more repetitions to develop a strong fear response to the conditioned images, indicating that stimulation slowed fear learning. However, they did eventually acquire the association, showing that the effect reduced learning speed rather than preventing it.
Quick to learn, slow to forget
The most notable effect appeared during extinction, when shocks stopped. Participants who had received amygdala-targeted ultrasound showed a faster decline in physiological fear responses after the aversive outcomes were removed—even though ultrasound was no longer applied. This suggests that memories formed while the amygdala was dampened are less “sticky” and more amenable to updating.
According to the researchers, the amygdala supports an emotional learning state characterized by rapid acquisition and slow forgetting. Modulating this state with transcranial ultrasound appears to shift that balance toward slower learning and quicker extinction.
Exposure therapy
These findings point toward potential clinical applications. In exposure therapy, patients are gradually and safely exposed to feared stimuli to reduce anxiety. If clinicians can stimulate the amygdala at the moment a fear memory is reactivated, they may be able to make that memory easier to update with new, non-threatening information—accelerating therapeutic benefits and improving outcomes for people with phobias or PTSD.
The current study demonstrates the effect during formation of new fear responses; further research will be needed to test whether the same approach can modify long-standing, pathological fear memories in clinical populations.
Key Questions Answered:
A: Not exactly. The procedure appears to reduce the emotional intensity of a memory rather than erase the memory itself. Participants still remembered which images had been paired with threat, but their bodily fear responses decreased more quickly during extinction.
A: The stimulation used is non-invasive and similar in principle to diagnostic ultrasound. In this study it caused no pain and no surgical intervention was required. Safety and long-term effects still need further study in larger and clinical samples.
A: The technique could be applied during exposure-based therapies to help update fear memories when they are reactivated, potentially making therapy faster and more effective by reducing the resistance of fear memories to change.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The journal article was reviewed in full by the editorial team.
- Additional context was added by staff for clarity.
About this neurotech and PTSD research news
Author: Lieneke van Dijk
Source: Radboud University
Contact: Lieneke van Dijk – Radboud University
Image credit: 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
This study provides causal evidence that the human amygdala is essential for rapidly acquiring cue-conditioned threat responses and that it contributes to forming threat memories that resist extinction. The researchers used transcranial ultrasound stimulation (TUS) to modulate the bilateral amygdala during Pavlovian threat conditioning in healthy adults.
Statistical models and computational analyses of trial-level skin conductance responses showed that amygdala-targeted TUS selectively slowed initial threat acquisition, enhanced subsequent extinction, and affected declarative memory for threat probability. The results highlight the amygdala’s role in an emotional learning state characterized by fast learning and slow forgetting and indicate the potential of TUS as a targeted neuromodulation tool for conditions such as PTSD, where persistent threat memories can undermine recovery.