Using functional ultrasound (fUS) technology, it can accurately map brain activity from precise regions deep within the brain at a resolution of 100 micrometers (the size of a single neuron is approximately 10 micrometers).
"Invasive forms of brain-machine interfaces can already give movement back to those who have lost it due to neurological injury or disease," says Sumner Norman, postdoctoral fellow in the Andersen lab and co-first author on the new study. "Unfortunately, only a select few with the most severe paralysis are eligible and willing to have electrodes implanted into their brain. Functional ultrasound is an incredibly exciting new method to record detailed brain activity without damaging brain tissue. We pushed the limits of ultrasound neuroimaging and were thrilled that it could predict movement. What's most exciting is that fUS is a young technique with huge potential--this is just our first step in bringing high performance, less invasive BMI to more people."
The new study is a collaboration between the laboratories of Richard Andersen, James G. Boswell Professor of Neuroscience and Leadership Chair and director of the Tianqiao and Chrissy Chen Brain-Machine Interface Center in the Tianqiao and Chrissy Chen Institute for Neuroscience at Caltech; and of Mikhail Shapiro, professor of chemical engineering and Heritage Medical Research Institute Investigator. Shapiro is an affiliated faculty member with the Chen Institute.
Ultrasound works by emitting pulses of high frequency sound and measuring how those sound vibrations echo throughout a substance, such as various tissues of the human body. Ultrasound can also "hear" the internal motion of organs. For example, red blood cells, like a passing ambulance, will increase in pitch as they approach the source of the ultrasound waves, and decrease as they flow away. Measuring this phenomenon allowed the researchers to record tiny changes in the brain's blood flow down to 100.
"A key question in this work was: If we have a technique like functional ultrasound that gives us high-resolution images of the brain's blood flow dynamics in space and over time, is there enough information from that imaging to decode something useful about behavior?" Shapiro says. "The answer is yes. This technique produced detailed images of the dynamics of neural signals in our target region that could not be seen with other non-invasive techniques like fMRI. We produced a level of detail approaching electrophysiology, but with a far less invasive procedure."
"Current high-resolution brain-machine interfaces use electrode arrays that require brain surgery, which includes opening the dura, the strong fibrous membrane between the skull and the brain, and implanting the electrodes directly into the brain. But ultrasound signals can pass through the dura and brain non-invasively. Only a small, ultrasound-transparent window needs to be implanted in the skull; this surgery is significantly less invasive than that required for implanting electrodes," says Andersen.
MEDICA-tradefair.com; Source: California Institute of Technology