A new study shows that ultrasound waves can activate brain circuits in living animals. Scientists from NYU Langone Health, the University of Zurich, and ETH Zurich conducted this research using mice. They developed a system that combines ultrasound sources with a fiberscope, a tiny camera used to see inside the body, to observe how specific brain areas respond to these sound waves. This approach could lead to new treatments for brain-related conditions like Parkinson’s disease or mental health disorders without needing surgery.
The study used transcranial ultrasound stimulation (TUS), a method that sends ultrasound waves through the skull to stimulate the neurons that carry signals in the brain. Unlike some existing treatments that use strong ultrasound to destroy neurons causing tremors in Parkinson’s, this study used lower-intensity waves to temporarily activate neurons. This activation can spread through connected brain circuits.
Observing brain activity
Observing TUS effects in a living brain is challenging. Studying neurons in a lab dish doesn’t show how ultrasound behaves in a real brain, where the skull and three-dimensional tissue affect the waves. For TUS to work safely, the waves must target precise brain areas with enough strength to pass through the skull but not so much that they harm delicate brain tissue. The researchers used a helmet-like device with 512 ultrasound emitters, which create and send out sound waves, placed above the mouse’s head. They shaped these waves into holograms, similar to how light creates three-dimensional images. These sound holograms focused on specific brain regions, like triangles or pentagons.
When the targeted neurons were activated, they produced a fluorescence signal, a glowing marker that the camera could detect. This allowed researchers to measure which brain areas responded to TUS. The study found that focusing on connected brain circuits made neurons up to ten times more sensitive to ultrasound, requiring less power and potentially making the treatment safer. The findings, published in Nature Biomedical Engineering, suggest TUS could be used to study brain circuits and develop non-invasive treatments for various conditions. The researchers plan to explore more complex circuits and deeper brain areas in future studies.