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.’