Researchers take a step towards a next-generation brain-computer interface system

PROVIDENCE, RI [Brown University] — Brain-computer interfaces (BCIs) are emerging assistive devices that could one day help people with brain or spinal cord injuries move around or communicate. BCI systems depend on implantable sensors that register electrical signals in the brain and use these signals to drive external devices such as computers or robotic prostheses.

Most current BCI systems use one or two sensors to sample up to a few hundred neurons, but neuroscientists are interested in systems that can collect data from much larger groups of brain cells.

Now, a team of researchers has taken a key step towards a new concept for a future BCI system – a system that uses a coordinated network of independent, wireless microscale neural sensors, each the size of a grain of salt. , to record and stimulate brain activity. The sensors, called “neurograins”, independently register the electrical impulses emitted by the neurons and send the signals wirelessly to a central hub, which coordinates and processes the signals.

In a study published Aug. 12 in Nature Electronics, the research team demonstrated the use of nearly 50 of these autonomous neurograins to record neuronal activity in a rodent.

The findings, the researchers say, are a step towards a system that could one day allow brain signals to be recorded in unprecedented detail, leading to new insights into how the brain works and new therapies for people with dementia. brain or spinal cord damage.

“One of the big challenges in the field of brain-computer interfaces is devising ways to probe as many points in the brain as possible,” said Arto Nurmikko, a professor at Brown’s School of Engineering and lead author of the study. “Until now, most BCIs have been monolithic devices – kind of like little beds of needles. Our team’s idea was to break this monolith down into tiny sensors that could be distributed across the cerebral cortex. C is what we have been able to demonstrate here.

The team, which includes experts from Brown, Baylor University, University of California San Diego and Qualcomm, began development work on the system about four years ago. The challenge was twofold, said Nurmikko, who is affiliated with Brown’s Carney Institute for Brain Science. The first part required reducing the complex electronics involved in sensing, amplifying and transmitting neural signals in the tiny silicon neurograin chips. The team first designed and simulated the electronics on a computer, and performed multiple manufacturing iterations to develop working chips.

The second challenge was to develop the body’s external communication hub that receives signals from these tiny chips. The device is a thin patch, about the size of a thumbprint, that attaches to the scalp outside the skull. It works like a miniature cellphone tower, using a network protocol to coordinate signals from neurograins, each with its own network address. The patch also wirelessly powers the neurograins, which are designed to operate with a minimal amount of electricity.

“This work was truly a multidisciplinary challenge,” said Jihun Lee, postdoctoral researcher at Brown and lead author of the study. “We had to bring together skills in electromagnetism, radio frequency communication, circuit design, manufacturing and neuroscience to design and operate the neurograin system.”

The goal of the new study was to demonstrate that the system could record neural signals from a living brain – in this case, the brain of a rodent. The team placed 48 neurograins on the animal’s cerebral cortex, the outer layer of the brain, and successfully recorded characteristic neural signals associated with spontaneous brain activity.

The team also tested the devices’ ability to stimulate the brain as well as record from it. Stimulation is done with tiny electrical impulses that can activate neural activity. The stimulation is driven by the same hub that coordinates neural recording and could one day restore brain function lost to disease or injury, the researchers hope.

The size of the animal’s brain limited the team to 48 neurograins for this study, but the data suggests that the system’s current configuration could support up to 770. Ultimately, the team plans to move to several thousand neurograins, which would provide a currently inaccessible picture of brain activity.

“This was a difficult undertaking, as the system requires simultaneous power transfer and wireless networking at a rate of megabits per second, and this must be accomplished under extremely tight silicon area and power constraints. “said Vincent Leung, a partner. Professor in the Department of Electrical and Computer Engineering at Baylor. “Our team has pushed the boundaries of distributed neural implants.”

There’s still a lot of work to do to make this comprehensive system a reality, but the researchers said this study represents a key step in that direction.

“Our hope is that we can ultimately develop a system that will provide new brain science insights and new therapies that can help those affected by devastating injuries,” Nurmikko said.

Other co-authors of the research were Ah-Hyoung Lee (Brown), Jiannan Huang (UCSD), Peter Asbeck (UCSD), Patrick P. Mercier (UCSD), Stephen Shellhammer (Qualcomm), Lawrence Larson (Brown) and Farah Laiwalla (Brown). The research was supported by the Defense Advanced Research Projects Agency (N66001-17-C-4013).