Nathan Copeland has been wearing a brain-computer interface (BCI) for seven years and four months—the longest a human has had an implant like this. Through the BCI, the 36-year-old can play video games and operate a prosthetic arm with his thoughts.
In 2004, a car accident left Copeland paralyzed from the chest down. Then he participated in a study at the University of Pittsburgh in 2014. It encouraged people with major spinal cord injuries to join and see if a BCI could restore some of the lost functionality. Without hesitation, he underwent brain surgery to install the implant, despite not knowing how long the device would keep working. At this point, the researchers thought that the BCI could last only five years, based on monkey data.
Ian Burkhart previously held the record for wearing a BCI implant for the longest time. But he had it removed in 2021 when his research study ended. Now there are more than 30 study participants worldwide wearing implanted BCIs.
The fact that Copeland’s implant is still functioning for more than seven years, without any complications or major side effects, is promising. It shows that the devices, which have been in development since the 1960s but are still experimental, are moving closer to commercial reality for patients with severe disabilities.
However, there are still questions about the long-term durability of the implants. Can they be upgraded? How much will their performance erode over time?
The Utah arrays
Copeland had four arrays installed—two in the part of the brain responsible for processing sensory information and two in the area that controls motor functions. Called Utah arrays, they are made of hard silicon, coated with a conductive metal, and look like a hairbrush.
Richard Normann conceived the Utah array in the 1980s as a professor of bioengineering at the University of Utah. It has since become the gold standard for BCI studies.
Utah array produced by Blackrock Neurotech
Neurons produce electrical fields when communicating with each other, so scientists use the Utah arrays to capture and record activity from hundreds of nearby neurons. Building a BCI requires researchers to decode those neural signals into digital commands that allow the user to operate a computer or a prosthetic limb. Copeland’s BCI includes:
An implanted array
A cable that spans the nickel-sized pedestal on his head to an external device that boosts his neural signals
A computer to decode those signals
The body is a hostile environment
The Utah array has stayed up to 10 years in monkeys, but with so few people testing these devices, their longevity in humans is still unknown. Although Copeland’s arrays are still working, it’s not as well as they did in the first year, said Robert Gaunt in an interview with Wired. Gaunt is a member of Copeland’s research team and a biomedical engineer at the University of Pittsburgh.
The human body is an aggressive environment. It’s the reason the implants’ performance degrades over time. Gaunt said it’s challenging to put engineered systems and electronics in the body as it’s always trying to get rid of these things.
Implanted arrays can evoke an immune response in the electrodes’ neural tissue. And studies have shown that inflammation in this area can lead to reduced signal quality. Furthermore, scars can form around brain implants, affecting their capability to collect signals from nearby neurons. And the less information a BCI can interpret from nearby neurons, the less effective it becomes at carrying out its intended functions.
The quest to make BCI implants last longer
Scientists are looking for ways to make implants last longer. One way is by experimenting with different materials. The Utah array is protected with parylene, a material used in the medical device industry for its low moisture absorptivity and stability. However, it’s also known to crack and corrode over time.
In an interview with Wired, Florian Solzbacher, chairman and co-founder of Blackrock Neurotech, which manufactures Utah arrays, said that the company is testing a new array coated with a combination of silicon carbide, which has been used as an industrial material for more than a century, and parylene. Although the company already has preliminary data on the performance of the new formulation in animals, it has yet to be used in people.
Scarring is a common issue with implants, so Paradromics, a BCI company based in Texas, is developing more flexible, thinner electrodes designed to be less disruptive to the tissue.
Softer materials may be better integrated into the brain than the rigid Utah array. A research team at the Massachusetts Institute of Technology is currently experimenting with hydrogel coatings, which possess an elasticity like that of the brain.
Another approach is to create smaller, less invasive implants. Researchers are currently testing neurograins—tiny chips the size of a grain of sand that could be sprinkled across the brain’s cortical surface. However, the system has only been tested in rodents.
Another concern is that multiple surgeries aren’t ideal, as each carries a risk of bleeding and infection at the implant site. This is relevant to research participants who have had their Utah arrays removed and replaced. According to Gaunt, it would be best if external BCI components were made upgradable.
But currently, one of the most significant risks for brain implants is an external part of most BCI systems—the pedestal. It sits on top of the skull and can cause infection, but the pedestal is necessary to connect the implanted array to the computer that decodes neural signals. Copeland and other study participants need their head pedestals to use the BCI.
As BCI longevity in humans is still unknown, Copeland knows his implant could stop working someday. But he tries his best not to worry about it.As of this publication, scientists are looking for ways to make the human body not reject the implant and allow it to last longer. But for now, we can only watch and wait.