oopsies —

It's unclear what caused the retraction or how many threads have become displaced.

Enlarge / Elon Musk, in Paris, France, on Friday, June 16, 2023. Musk predicted his Neuralink Corp. would carry out its first brain implant later that year. The first implantation took place in January 2024.

The first invasive brain chip that Neuralink embedded into a human brain has malfunctioned, with neuron-surveilling threads appearing to have become dislodged from the participant's brain, the company revealed in a blog post Wednesday.

It's unclear what caused the threads to become "retracted" from the brain, how many have retracted, or if the displaced threads pose a safety risk. Neuralink, the brain-computer interface startup run by controversial billionaire Elon Musk, did not immediately respond to a request for comment from Ars. The company said in its blog post that the problem began in late February, but it has since been able to compensate for the lost data to some extent by modifying its algorithm.

Neuralink touts that its invasive implant includes 64 flexible threads carrying a total of 1,024 electrodes that can detect neuronal activity. Those flexible threads—described as thinner than a human hair—are inserted individually into the brain by the company's proprietary surgical robot. The goal is for the threads to be placed near neurons of interest so that signals detected by the electrodes can be recorded and decoded into intended actions, such as moving a cursor on a computer screen.

On January 28, the company announced that it has surgically implanted its brain-computer interface into its first clinical trial participant, 29-year-old Noland Arbaugh, who developed quadriplegia after a 2016 diving accident. The surgery took place at Barrow Neurological Institute in Phoenix. Musk announced on social media on January 29 that Arbaugh was "recovering well" and that the initial results were "promising."

Since then, Neuralink and Arbaugh have released video and livestreams of Arbaugh playing video games, using only his implant to make moves in a chess game and control characters in Mario Kart, for instance. The only hint of trouble was on March 1 when Arbaugh answered questions in an all-hands meeting with Neuralink in which he said at one point: "Sure we’re still working out the kinks and stuff. But once we get this figured out, there’s no reason for [the implant] not to be out there," according to The Wall Street Journal.

The Journal was the first to report that an unknown number of threads have become displaced in Arbaugh's brain. Neuralink posted its blog confirming the problem after the Journal published the report.

It remains unclear why the threads moved from their placement, but one hypothesis that sources told the Journal is that there was air trapped inside Arbaugh's skull after the surgery, a condition called pneumocephalus. The sources familiar with Neuralink's trial said that the possibility of removing the implant was considered after the problem was identified.

Arbaugh's safety does not appear to be negatively impacted. However, the company reported that the retraction of the threads lowered his bits-per-second (BPS) rate, which is used to measure how quickly and accurately a patient with an implant can control a computer cursor. Neuralink was able to restore the BPS rate to the level seen before retraction by modifying the algorithm that decodes the electrode signals. According to Neuralink, the tweaks included making the implant "more sensitive to neural population signals," improving the techniques to translate these signals into cursor movements, and enhancing the user interface. The company reported improved and sustained BPS rates after the changes.

The Journal reported that the company has told the Food and Drug Administration—which regulates clinical trials and granted approval for Neuralink to test its device in humans—that it believes it has fixes for the problem. The company is hoping to carry out two more implantations in the coming months, with a total of 10 this year.

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