Devices that can stimulate deep regions of the brain have been in development as treatment options for disorders like epilepsy and Parkinson's disease, but they need to be surgically implanted and left in place. Researchers are trying to create a less invasive method for triggering activity in neurons that are involved in the control of motor function. Now reporting in Brain Stimulation, a team of scientists is finding success in a technique that combines ultrasound and genetic technologies. The tool has been called sonothermogenetics.
"Our work provided evidence that sonothermogenetics evokes behavioral responses in freely moving mice while targeting a deep brain site," noted study leader Hong Chen, assistant professor of biomedical engineering in the McKelvey School of Engineering and of radiation oncology at the School of Medicine at WUSTL. "Sonothermogenetics has the potential to transform our approaches for neuroscience research and uncover new methods to understand and treat human brain disorders."
In this study, the researchers used a genetic construct that carried the code for TRPV1 ion channels and delivered it to specific neurons. Next, select neurons were exposed to a small burst of heat that came from a wearable, low-intensity, focused ultrasound device. The heat emitted was only a little warmer than body temperature, but it was enough to activate the TRPV1 ion channels, which can act as switches that turn neurons on or off.
"We can move the ultrasound device worn on the head of free-moving mice around to target different locations in the whole brain," said first study author Yaoheng Yang, a graduate student in biomedical engineering. "Because it is noninvasive, this technique has the potential to be scaled up to large animals and potentially humans in the future."
This tool may one day be used to target different places in the brain. Right now, it can be directed at any location in the mouse brain, without damaging it, Chen noted. This work builds on previous research that showed how ultrasounds can affect ion channels, and the researchers are planning to continue to refine this technology.