In a groundbreaking study, scientists have demonstrated the potential to use ultrasound waves to monitor human brain activity. For the first time, researchers have utilized ultrasound to observe inside a person’s brain. The subject’s brain activity was recorded as he performed various tasks outside a medical facility, including playing a video game.
To enable this, the researchers implanted a special material into the man’s skull that allowed ultrasound waves to penetrate. These waves, after passing through the “acoustically transparent” window, bounced off tissue boundaries within the brain. The returning waves were captured by an ultrasound probe connected to a scanner, creating a detailed image of brain activity, much like how ultrasounds visualize a fetus.
The team focused on changes in blood volume in specific brain regions, such as the posterior parietal cortex and the motor cortex, both of which are crucial for coordinating movement. By monitoring blood volume, they could indirectly track neuronal activity, as more active neurons require increased oxygen and nutrients delivered by blood vessels.
This study builds on previous research conducted on nonhuman primates. By working with a human subject, scientists were able to use ultrasound imaging to precisely monitor neural activity as the subject engaged in activities like playing a connect-the-dots game and strumming a guitar. Their findings were published on May 29 in the journal *Science Translational Medicine*.
Dr. Charles Liu, a co-senior study author and neurosurgeon at the University of Southern California, noted that the ultrasound data revealed the subject’s intentions, such as moving a joystick or strumming a guitar, in real-time.
Functional ultrasound imaging, which tracks changes in blood volume in the brain, offers a promising alternative to traditional techniques like functional magnetic resonance imaging (fMRI). This method is more sensitive to brain activity changes, provides higher resolution images, and doesn’t require patients to remain still in a machine for long periods, allowing for real-life setting observations.
Historically, the human skull has blocked ultrasound waves, but Liu and his team overcame this by using a patient who had a portion of his skull removed to alleviate pressure from a severe traumatic brain injury (TBI). Instead of the typical titanium mesh or custom-built implant used in such cases, the team used an acoustically transparent implant. The study authors suggest that this technique could eventually benefit a broader range of patients, not just those with TBI.
Mikhail Shapiro, co-senior study author and professor at Caltech, emphasized the potential applications of this technology, noting that many patients undergoing skull removal procedures could benefit from a cranial implant transparent to ultrasound signals.
