BCIs (brain-computer interfaces) are a new type of assistive gadget that could enable patients with brain or spinal injuries to move and communicate. Implantable sensors capture electrical impulses in the brain and use those signals to control external devices such as computers or robotic prostheses in BCI systems.
Most existing BCI systems employ one or two sensors to sample up to a few hundred neurons, but neuroscientists want devices that can collect data from far larger groups of brain cells.
A group of researchers has taken a significant step toward a novel concept for a future BCI system that records and stimulates brain activity using a coordinated network of independent and wireless microscale neural sensors, each approximately the size of a grain of salt. The “neurograins” sensors record the electrical pulses produced by firing neurons individually and communicate the signals wirelessly to a central hub that interprets and coordinates the signals.
The research team showed the use of approximately 50 independent neurograins to record neural activity in a rodent in an article published in Nature Electronics on August 12, 2021.
According to the researchers, the findings represent a step toward a technology that could one day allow for the unprecedented recording of brain impulses, leading to new insights into how the brain operates and new therapies for those with brain or spinal injuries.
The system was developed by a team of professionals from Brown University, Baylor University, the University of California in San Diego, and Qualcomm over four years. According to Nurmikko, who is linked with Brown’s Carney Institute for Brain Science, the problem was twofold. The initial step was to compress the complicated electronics used to detect, amplify, and transmit neural impulses into small silicon neurograin chips. To build functioning chips, the team initially developed and simulated the circuitry on a computer before going through numerous fabrication rounds.
The body-external communications hub that accepts messages from those tiny chips was the second challenge. The gadget is a thin patch that attaches to the scalp outside the skull and is roughly the size of a thumbprint. It functions similarly to a miniature cell phone tower, using a network protocol to coordinate signals from the neurograins, each with its own network address. The patch also provides wireless power to the neurograins, designed to run on very little electricity.
This new study aimed to show that the device could record neural impulses from a living brain, in this case, a rodent’s brain. The researchers implanted 48 neurograins in the animal’s cerebral cortex, which is the brain’s outer layer, and successfully captured distinctive neural signals associated with spontaneous brain activity.
The scientists also examined the devices’ ability to both stimulate and record from the brain. Small electrical pulses are used to activate brain activity during stimulation. Researchers hope that the stimulation, controlled by the same hub that controls neural recording, will one day be able to restore brain function lost due to disease or injury.
The researchers were limited to 48 neurograins for this investigation due to the size of the animal’s brain, but the data suggests that the system’s current setup might support up to 770. The team hopes to eventually scale up to tens of thousands of neurograins, providing a hitherto unreachable picture of brain activity.
There is still tremendous work to make that whole system a reality, but experts believe this study is a critical first step.
The ultimate goal is to create a system that will reveal new scientific insights into the brain and new medicines to help people who have suffered catastrophic injuries.