Here’s what you’ll learn when you read this story:
- Researchers have developed new technology to scan the human brain in real time while the patient moves around.
- Called functional ultrasound imaging (fUSi), this new type of scan is unprecedented in precision and depth.
- However, to have your brain monitored in this way, you have to agree to have a small window cut into your skull.
The human brain is simultaneously the source of our scientific curiosity as well as a subject of it. Everything that makes us human is housed inside our brain, but exactly how those pieces of soft tissue come together to create us is a question that has puzzled scientists for centuries. We know a lot more about our brains today—like which region is responsible for feelings of fear (that would be the amygdala)—but much of that information is based on experiments conducted in a controlled laboratory environment.
How our brains behave out in the wild is a tougher question to answer, and it’s exactly what scientists at Erasmus University Medical Center in the Netherlands set out to investigate in a recent study, published in June in the journal Science Advances. In it, researchers used functional ultrasound imaging (fUSi) to monitor brain activity in a study subject as the individual moved about an open space.
There’s just one rather technical catch: prior to the study, surgeons first needed to cut a small window into the patient’s skull. It sounds extreme, but the study’s first author, Sadaf Soloukey, Ph.D., says the potential benefits of this imaging technique outweigh the discomforts.
“People have asked me, do patients want to do this?” says Soloukey, a neurosurgical resident at Erasmus. “So far, people we’ve spoken to are willing to do it—mostly because they want to help science but also because they see it has a potential benefit . . . so they’re willing to do something that’s a bit unusual.”
On the more practical side, research suggests functional ultrasound imaging could make brain surgery more safe when conducted on patients who are awake, and it could also shed new light on mental health disorders like major depression. In the future, researchers expect to downsize fUSi technology into a wearable that can monitor your brain 24/7—making the possibilities for studying the inner machinations of the human mind nearly endless.
At its core, fUSi is no different from ultrasound imaging used on any other part of the body, such as prenatal ultrasounds used to assess the development of a baby in the womb. Ultrasound technology works by emitting high-frequency sound waves that bounce off structures and provide data that can be translated into 2D models; you can picture this like the mold created when you press your face or hand into a pin art toy.
For brain imaging, fUSi measures changes in blood flow as a proxy for brain activity, Soloukey explains. While this approach may be more invasive than other brain imaging techniques—like an electroencephalogram (EEG), which measures brain activity through electrodes placed on the scalp, or functional magnetic resonance imaging (fMRI), which measures brain activity by detecting changes in blood flow during an MRI scan—it can offer a precision and depth that the others simply can’t.
For instance, EEGs provide a “superficial measure” of brain activity, Soloukey says. And fMRI scans rely on MRI machines that use highly powerful magnets and become extremely hot, making airflow crucial. And that same ventilation can introduce data artifacts into the scan, which are forms of distortion, she explains. So, you can’t use an fMRI to effectively conduct spoken-word functional tasks with a patient because their speech—and even tiny movements of the head, jaw, tongue, or lips—can disturb the air while the scan is taking place.
That’s where functional ultrasound imaging came in.
To conduct their experiment, the researchers recruited a study participant who already had a medical-grade plastic “window” placed in their skull during a previous brain surgery. The team then created a custom, 3D-printed helmet designed to hold a fUSi probe in place while it monitored brain activity through the window. The helmet looks a little like a superhero mask that covers the wearer’s head, nose, and cheeks with an opening for the eyes. It also allows a cable to protrude off the top where the probe is positioned over the skull window.
While this window may seem like an inconvenience, Soloukey explains that it’s necessary in order to receive clear data from the ultrasound. Otherwise, the skull would distort that precious data.
Over the course of two years, the research team collected fUSi data while the participant completed functional, everyday tasks like brushing a hand across their face, licking their lips, and walking in a straight line for nearly 100 feet while pushing a mobility cart. At the end of their experiment, the team determined that the fUSi helmet provided the same level of performance as a stationary fMRI.
This is an important benchmark, Soloukey says, because it shows that fUSi can be used in place of other brain imaging techniques in applications like improving safety during brain surgery in which patients are awake as well as in experiments to learn more about the brain’s behavior in daily life.
This could even include the study of mental health disorders like major depression, says Claire Nastaskin, Ph.D., an ultrasound neurophysiologist who contributed to fUSi research in a 2024 Science Translational Medicine paper. Depression can present differently in the brain from moment to moment, she says, and having data about how this disorder appears in a patient’s brain throughout a day in a natural environment may help scientists better understand and treat depressive episodes.
Still, cutting a hole in your skull and wearing a bulky helmet in your daily life may not seem like an attractive option. Soloukey and Nataskin say that this technology will continue to advance toward smaller and less invasive options. Instead of a skull window that is several centimeters wide, future fUSi devices may only need a hole the size of a dime, and a helmet may be replaced with an implantable device that can provide 24/7 brain monitoring.
This future implant would be less like Elon Musk’s Neuralink, which Nataskin says only provides a small snapshot of brain activity, and more similar to implants used to treat seizures in patients with drug-resistant epilepsy. For patients with depression, a fUSi implant could help scientists better understand the brain state during a depressive episode and how this intersects with daily life.
“I hope we find brain signatures that relate to [what] influences patient symptoms, like fluctuations based on time of year or hormonal changes,” Soloukey says. “If we can detect the predecessors of those elements that predict that it will happen, [then] you could maybe find better timing to do a treatment or to change a medication regimen.”
This kind of 24/7 monitoring could go on in the background and transmit data to a patient’s health care team. But receiving your own data directly, á la fitness wearable, may not be the best choice for a patient’s peace of mind, she says. Sometimes ignorance really is bliss.
All of these future uses are at least 10 years away, says Soloukey, but she’s hopeful that these advances will make fUSi techniques more widely accessible for both surgeons and neuroscientists who want to get a clearer look into how our brains really work.
Sarah is a D.C.-based independent science journalist interested in the philosophical questions of science and technology and how research intersects with our daily lives. Her work has appeared in Live Science, Nature, Popular Science, and Science News Explores, among other outlets, and covers topics ranging from AI to particle physics and space travel.