Rather than building a device from scratch, Synchron and Paradromics have taken inspiration from previous medical devices. The Paradromics design, for example, is based on the Utah set, but introduces some key improvements. It’s wireless, for example, and has 421 electrodes on the end of small wires found in brain tissue. All of those cables are much smaller than the stems on the Utah set, Angle says.
Meanwhile, Synchron’s device is a hollow mesh tube that resembles a heart stent. Instead of going directly to the brain, it is inserted into the jugular vein at the base of the neck and pushed against the cortex. Synchron has implanted his device in 10 participants so far, and one of them has surpassed three years with it. (Arbaugh’s implant is still working after 100 days.) Banerjee says the company has not yet seen a decline in signal quality or performance.
Andrew Schwartz, a professor of neurobiology at the University of Pittsburgh who builds brain-computer interfaces, also speculates that Neuralink’s design may have caused the implanted threads to exit the brain.
The outermost layer of the brain, the dura mater, must be opened to place the device. “With multiple leads inserted individually into the cortex, it can be difficult to suture the dura mater closed after the leads are implanted,” she says. Leaving this opening could have caused scar tissue to form around the opening, causing the threads to pull out. The Utah matrix, Schwartz says, is designed so that the dura mater can be sutured closed after implantation.
Despite Neuralink’s setback, the company managed to livestream a demo of its device on March 20, showing Arbaugh using the implant to play chess just by thinking about it. Arbaugh has also used the device to play the video game. Mario Kart. “I just can’t describe how cool it is to be able to do this,” he said. he said in the video.
In the blog post, Neuralink says it compensated for the lost threads by modifying the recording algorithm to make it more sensitive to neural signals. He also says that he improved the way it translated those signals into cursor movements and improved its user interface, and that these changes were able to improve the device’s performance.
To move a cursor, Angle says having more electrodes doesn’t matter much. But for more complex tasks, such as converting text to speech, a higher data speed will be important.
Before receiving the implant, Arbaugh used a handheld stylus, known as a mouth cane, to operate a tablet that had to be placed by a caregiver. A buccal swab can only be used in an upright position and prevents normal speech. When used for long periods, it can cause discomfort, muscle fatigue, and pressure sores.
For Arbaugh, Neuralink’s device is a “luxury overload,” according to the company’s blog post. He still uses the implant, which has allowed him to “reconnect with the world” and get back to doing things on his own without needing his family at all hours of the day and night.
“It’s good that the patient can still use the device and is satisfied with it. At the end of the day, that’s a win,” Angle says. “But from our perspective, companies that are building brain-computer interfaces need to create devices that are robust and reliable over a period of several years.”
There are likely to be setbacks on the path to commercializing brain-computer interfaces, and with Neuralink taking a unique approach with its device, the company could face more obstacles along the way.