As it penetrates the tissue, the Utah array can cause inflammation and scarring around the implant site, leading to a decrease in signal quality over time. And signal quality is important because it affects how well the BCI performs. No one actually knows how long Utah arrays can persist in the brain; so far the record is held by Nathan Copeland, whose device is now in its eighth year.
Placing a Utah array also requires surgeons to perform a craniotomy, which involves making a small hole in the skull. It is a major procedure that can cause infection and bleeding, and recovery takes a month or more. Understandably, many patients are hesitant to undergo one, even if it means regaining some level of communication or mobility.
Precision is trying to solve both problems with a device that has 1,024 electrodes but is ultra-thin — about one-fifth the thickness of a human hair — and doesn’t penetrate brain tissue. Instead of a craniotomy, it would be placed using a minimally invasive procedure that involves making a small slit in the skin and skull and then sliding the implant onto the outer layer of the brain called the cortex. “Just the idea of doing more damage to the brain or nervous system that is already damaged is pretty fraught,” says Rapoport, who also co-founded Neuralink. He thinks streamlining the procedure would make these systems much more attractive to patients.
Craig Mermel, the company’s president and chief product officer, says the Precision array is also just as easy to remove. As BCI technology improves, patients who receive early brain chips may eventually want to upgrade to new ones. With Utah arrays, new devices usually cannot be placed in the same area due to scar tissue.
With more than 1,000 electrodes, Mermel says, Precision’s device will be able to provide higher resolution of brain activity than current arrays. Precision’s arrays are also modular in design. Several can be connected together to collect brain signals from a larger area. For more precise or complex actions beyond stimulating basic body movements or activating simple computer functions, “you want more coverage of brain areas,” says Mermel.
Peter Brunner, an associate professor of neurosurgery and biomedical engineering at Washington University in St. Louis, says Precision’s implant looks impressive, but it’s still unknown how long it will last once implanted. Any device implanted in the body has a tendency to break down over time. “There’s a tension between making things smaller while maintaining robustness against the environment these devices face in the human body,” he says.
The brain shifts in the skull, and so does an implant, says Brunner. A surface array may be able to move around more than one entering the brain. He says even a micrometer shift can change which group of neurons the device registers, which could affect how well the BCI works.
Rapoport says all the electrodes move a bit over time, but Precision’s software, which decodes the neural signals, can pick up on those tiny shifts.