This article first appeared in The Checkup, MIT Technology Review’s weekly biotech newsletter. To receive it in your inbox every Thursday, and read articles like this first, sign up here. 

In the world of brain-computer interfaces, it can seem as if one company sucks up all the oxygen in the room. Last month, Neuralink posted a video to X showing the first human subject to receive its brain implant, which will be named Telepathy. The recipient, a 29-year-old man who is paralyzed from the shoulders down, played computer chess, moving the cursor around with his mind. Learning to control it was “like using the force,” he says in the video.

Neuralink’s announcement of a first-in-human trial made a big splash not because of what the man was able to accomplish—scientists demonstrated using a brain implant to move a cursor in 2006—but because the technology is so advanced. The device is unobtrusive and wireless, and it contains electrodes so thin and fragile they must be stitched into the brain by a specialized robot. It also commanded attention because of the wild promises Neuralink founder Elon Musk has made. It’s no secret that Musk is interested in using his chip to enhance the mind, not just restore function lost to injury or illness.  

But Neuralink isn’t the only company developing brain-computer interfaces to help people who have lost the ability to move or speak. In fact, Synchron, a New York–based company backed by funding from Bill Gates and Jeff Bezos, has already implanted its device in 10 people. Last week, it launched a patient registry to gear up for a larger clinical trial.

Today in The Checkup, let’s take a look at some of the companies developing brain chips, their progress, and their different approaches to the technology.

Most of the companies working in this space have the same goal: capturing enough information from the brain to decipher the user’s intention. The idea is to aid communication for people who can’t easily move or speak, either by helping them navigate a computer cursor or by actually translating their brain activity into speech or text.

There are a variety of ways to classify these devices, but Jacob Robinson, a bioengineer at Rice University, likes to group them by their invasiveness. There’s an inherent trade-off. The deeper the electrodes go, the more invasive the surgery required to implant them, and the greater the risks. But going deeper also puts the electrodes closer to the brain activity these companies hope to record, which means the device can capture higher-resolution information that might, say, allow the device to decode speech. That’s the goal of companies like Neuralink and Paradromics. 

Robinson is CEO and cofounder of a company called Motif Neurotech, which is developing a brain-computer interface that only penetrates the skull (more on this later).  In contrast, Neuralink’s device has electrodes that go into the cortex, “right in the first couple of millimeters,” Robinson says. Two other companies—the Austin-based startup Paradromics and Blackrock Neurotech—have also developed chips designed to penetrate the cortex.

“That allows you to get really close to the neurons and get information about what each brain cell is doing,” Robinson says. Proximity to the neurons and a greater number of electrodes that can “listen” to their activity increases the speed of data transfer, or the “bandwidth.” And the greater the bandwidth, the more likely it is that the device will be able to translate brain activity into speech or text. 

When it comes to the sheer amount of human experience, Blackrock Neurotech is far ahead of the pack. Its Utah array has been implanted in dozens of people since 2004. It’s the array used by academic labs all over the country. And it’s the array that forms the basis of Blackrock’s MoveAgain device, which received an FDA Breakthrough Designation in 2021. But its bandwidth is likely lower than that of Neuralink’s device, says Robinson. 

“Paradromics actually has the highest-bandwidth interface, but they haven’t demonstrated it in humans yet,” Robinson says. The electrodes sit on a chip about the size of a watch battery, but the device requires a separate wireless transmitter that is implanted in the chest and connected to the brain implant by a wire.

There’s a drawback to all these high-bandwidth devices, though. They all require open brain surgery, and “the brain doesn’t really like having needles put into it,” said Synchron founder Tom Oxley in a 2022 TED talk. Synchron has developed an electrode array mounted on a stent, the very same device doctors use to prop open clogged arteries. The “Stentrode” is delivered via an incision in the neck to a blood vessel just above the motor cortex. This unique delivery method avoids brain surgery. But having the device placed above the brain rather than in it  limits the amount of data it can capture, Robinson says. He is skeptical the device will be able to capture enough data to move a mouse. But it is sufficient to generate mouse clicks. “They can click yes or no; they can click up and down,” he says.

Newcomer Precision Neuroscience, founded by a former Neuralink executive, has developed a flexible electrode array thinner than a human hair that resembles a piece of Scotch tape. It slides on top of the cortex through a small incision. The company launched its first human trials last year. In these initial studies, the array was implanted temporarily in people who were having brain surgery for other reasons. 

Last week, Robinson and his colleagues reported in Science Advances the first human test of Motif Neurotech’s device, which only penetrates the skull. They temporarily placed the small, battery-free device, known as the Digitally Programmable Over-brain Therapeutic (DOT), above the motor cortex of an individual who was already scheduled to undergo brain surgery. When they switched the device on, they saw movement in the patient’s hand. 

The ultimate goal of Motif’s device isn’t to produce movement. They’ve set their sights on a completely different application: alleviating mood disorders. “For every person with a spinal cord injury, there are 10 people suffering major depressive disorder and not responding to drugs,” Robinson says. “They’re just as desperate. It’s just not visible.”But the study shows that the device is powerful enough to stimulate the brain, a first step toward the company’s goals. 

The device sits above the brain, so it won’t be able to capture high-bandwidth data. But because Motif isn’t actually trying to decode speech or help people move things with their mind, they don’t need it to. “Your emotions don’t change nearly as quickly as the sounds coming out of your mouth,” Robinson says. 

Which of these companies will succeed remains to be seen, but with the momentum the field has already gained, controlling technology with your mind no longer seems like the stuff of science fiction. Still, these devices are primarily intended for people who have serious physical impairments. Don’t expect brain implants to achieve Neuralink’s goals of “redefining the boundaries of human capability” or “expanding how we experience the world” anytime soon. 

Now read the rest of The Checkup

Read more from Tech Review’s archive

Elon Musk claimed he wants to use brain implants to increase “bandwidth” between people. But the idea of extra-fast communication is “largely hogwash,” said Antonio Regalado in a previous issue of The Checkup. In some instances, however, bandwidth really does matter. 

Last year I wrote about two women who, thanks to brain implants, regained the ability to communicate. One device translated the intended muscle movements of the mouth into text and speech. The other decoded speech directly. 

Phil Kennedy, one of the inventors of brain-computer interfaces, ended up getting one himself in pursuit of data. This fascinating and bizarre story from Adam Piore really delivers. 

Long read: This 2021 profile of one brain implant user, by Antonio Regalado, covers almost everything you might want to know about brain implants and dives deeper into some of the technologies I mention above. 

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