A research team at Carnegie Mellon University has developed a new noninvasive brain stimulation technique, by showing how focused ultrasound affects the human brain. Using brainwave recordings from human participants, the team found that focused ultrasound can subtly influence brain activity without directly causing neurons to fire. The work clarifies conflicting results in the field and introduces a new approach to noninvasive brain stimulation. The study is published in Nature Communications.
Focused ultrasound has been studied for years, but its effects in humans are not well understood. One challenge is that the technology makes a quiet beeping sound that can trigger hearing pathways in the brain, making it hard to know whether changes are caused by the sound or by the ultrasound itself. Previous studies using MRI scans may also produce misleading signals.
To address these limitations, researchers conducted a resting-state study in 27 human participants using concurrent whole-brain EEG recordings. They compared low-intensity transcranial focused ultrasound (tFUS) alone, a mild electrical brain stimulation called tDCS, and a new approach that combines the two, deemed transcranial electro-acoustic stimulation (tEAS). When used alone, neither ultrasound nor electrical stimulation caused clear, targeted brain responses. However, when combined, they produced strong, specific activity in the targeted area.








