Focused ultrasound subtly primes human brain to respond, EEG study finds

A) The experiment consisted of applying neuromodulation to eyes-closed resting-state humans. B) A diagram of the experimental set up for each condition is provided with tDCS electrodes and ultrasound transducers placed on their relative location to EEG electrodes. C) A free water scan of ultrasound is provided to illustrate its 5 mm full-width half-max (−6 dB) spatial specificity. D) For the experiment, 500 kHz fundamental frequency (f0) ultrasound was pulsed every two seconds with up to an additional 20% random jitter for 200 trials. Credit: Nature Communications (2026). DOI: 10.1038/s41467-026-69853-8

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.

“This combination of ultrasound with electricity allowed us to see what ultrasound is really doing in the human brain,” said Bin He, professor of biomedical engineering at Carnegie Mellon University. “It helps explain why earlier studies seemed to show different results.

“Understanding that focused ultrasound can gently prime the brain opens the door to new treatments that are precise, noninvasive, and potentially safer for patients.”

The team also created a companion computer model to explain their findings. It shows that small effects from ultrasound and mild electrical stimulation can add together to trigger a full response in neurons. This helps make sense of why past studies sometimes seemed inconsistent.

“By showing that focused ultrasound acts as a gentle modulator, rather than a direct stimulator, we laid the groundwork for a new brain stimulation method,” explained He. “This combined approach, called transcranial electro-acoustic stimulation, or tEAS, uses the precision of ultrasound while producing stronger, targeted brain responses, and allows us to see what ultrasound is really doing in the human cortex.”

In the next phase, He and his team will build on the foundational understanding of focused ultrasound in the human brain established by this work to further integrate transcranial focused ultrasound with brain-computer interfaces, advancing human-machine interaction. They also plan to apply the novel transcranial electro-acoustic stimulation technique to the treatment of neurological disorders, including chronic pain and epilepsy.