Neuralink, the brain-computer interface startup led by Elon Musk, has achieved another milestone as the U.S. Food and Drug Administration (FDA) gave a green light for the company to implant its brain chip in a second person as soon as next month, the Wall Street Journal first reported today (May 20). The regulatory clearance follows Neuralink’s first human trial in January, which experienced malfunction post-implantation but the company has proposed solutions to the issues in the next test.

Neuralink’s first human patient shares experience

In January, Noland Arbaugh, a 30-year-old quadriplegic who had no movement below his shoulders for eight years following a spinal cord injury, underwent a surgery to have Neuralink’s N1 implant installed beneath his skull. The chip, roughly the size of a coin, has 64 external threads, each thinner than a human hair, that are inserted into the brain’s motor cortex to transmit neural signals. Following his surgery, Arbaugh was able to control a computer cursor solely through his thoughts, allowing him to communicate with friends, play games and interact with the digital world in ways he thought impossible after his accident.

However, about a month post-implantation, the device began to malfunction as most of its ultrathin threads came loose. In an interview with Good Morning America that aired on Friday (May 17), Arbaugh said he got emotional and was afraid he would lose all the enhancements the implant had brought to his life. “It was very, very hard to give up all of the amazing things that I was able to do. I think I had cried afterwards,” he said.

After the malfunction, Neuralink found that only about 15 percent of the threads remained in place in Arbaugh’s brain. Through software modifications, the company was able eventually help restore many of the device’s functionalities, allowing Arbaugh to retain those physical capabilities.

Despite the setback, Arbaugh remains positive about the potential of Neuralink’s technology. “It’s going to be amazing when someone can have a spinal cord injury, go into a hospital, get surgery, and walk out a couple of days later. I think it’s gonna happen,” he said on Good Morning America.

Arbaugh’s procedure is part of Neuralink’s PRIME study. The company continues to monitor Arbaugh’s progress closely and is using the data collected to improve future iterations of the implant. The company aims to “create a generalized brain interface to restore autonomy to those with unmet medical needs today and unlock human potential tomorrow,” according to its website.

Embedding threads deeper into the brain

Among critical insights learned from its initial human trail, Neuralink said it discovered that the brain could move up to three times more than expected, leading to the decision to embed the threads deeper into the brain’s motor cortex—from the initial three-to-five millimeters to eight millimeters—in the upcoming trial, the Journal reported.

Neuralink is looking to test its brain chip in two new patients in the coming months and aims to implant ten participants this year. The company has received interest from over 1,000 quadriplegics, it said, though fewer than 100 meet the criteria for the study. One issue is that the current patient registry predominantly consists of white males, sources told the Journal, while the company is seeking a diverse group to study various behaviors.

Neuralink was founded by Musk and a group of scientists and engineers in 2016. Before this year’s human trial, the company has tested its brain implant in animals such as pigs, monkeys and rats, which spurred intense ethical scrutiny. Skeptics of Neuralink’s core technology have questioned its novelty, saying the use of brain-computer interfaces in animals has been studied in the research community for years.