It’s been a long time since Alice Charton got a good look at a human face. There are plenty of people moving through her world, of course—her husband, her friends, her doctors, her neighbors—but judging just by what she can see, she’d have to take it as an article of faith that any one person was there at all. It was five years ago that the 87-year-old retired schoolteacher, living in a suburb of Paris, first noticed her eyesight failing, with a point in the middle of her field of vision going hazy, muddy, and dim. Soon that point grew into a spot, and the spot into a blotch—until it became impossible for her to recognize people, read a book, or navigate unfamiliar places on the streets.
The cause of the problem was age-related macular degeneration (AMD), a disease that afflicts some 200 million people worldwide and involves a breakdown of the cells in the retina, particularly in the area known as the macula, which is responsible for central vision. AMD does not typically cause blindness, but vision can be severely impaired. As for a cure for AMD? Nonexistent.
“I always worked with children, teaching them how to read,” says Charton. “So it was especially devastating for me not to be able to read.”
But three years ago, everything changed. After battling two years of slowly deteriorating vision, Charton was able to claw back a small portion of her lost world. Today, while she still can’t see faces or walk the streets unassisted, she does read—not very much; just an hour in the morning and an hour in the afternoon. But restoring even that small portion of her lost sight was transformative. “This brought me hope,” she says. “It literally changed my life.”
The breakthrough came about thanks to the work of Science Corp., a four-year-old neuroscience company based in San Francisco and led by biomedical engineer Max Hodak. In an experimental procedure dubbed Prima, which the company has now performed on a few dozen people, surgeons working with the company implant a 2-mm-by-2-mm computer chip with 400 hexagonal electrodes directly on the spot in the retina that the AMD has destroyed. Patients like Charton then put on a pair of bulky, black plastic glasses equipped with a tiny camera that looks out on the world and beams what it sees in an infrared impulse directly to the chip. The system uses the infrared wavelength—invisible to the naked eye—as opposed to visible light to prevent the signals from interfering with the residual peripheral vision the subjects still have. From the chip, the signal is transmitted to the optic nerve and then to the brain, restoring something resembling normal vision.
The chip that works this optical magic is not much to see. Under a powerful microscope attached to a computer at the Science headquarters, it resembles an oversize circuit board. To the naked eye, it is a tiny flake of nothing, but a flake of nothing that brings sight—imperfect, maybe, but sight all the same—to the nearly blind.
“There is an eye chart that [healthy] people are supposed to be able to read at a distance of 4 meters; even at 1 meter, untreated patients can barely read the biggest letters on the top line, using their peripheral vision,” says Hodak. “In a clinical trial of Prima, patients were able to read down to the fifth line on the eye chart.”
That trial, just published in the New England Journal of Medicine, involved 38 patients, including Charton, recruited from across Europe, all of whom underwent the Prima procedure. Postsurgery, nearly 80% of them improved their performance on the eye chart by 20 letters, and 84% of them could read letters, numbers, and words at home.
“AMD patients in our clinical trial were able to read and write again, not just letter by letter but word by word,” said Daniel Palanker, professor of ophthalmology and electrical engineering at Stanford University, in a statement that accompanied the release of the journal study. Palanker conceived of the Prima system in 2004, and has recently been working closely with Hodak and the Science team, serving as a part-time consultant on the Prima project. “The next-generation implant should have pixels that are five times smaller and more of them, going from about 400 in the current implant to 10,000. This should allow for visual acuity of 20/80, and with the help of the camera’s zoom function could even reach the equivalent of 20/20 resolution.”
Science Corp. is not stopping there. The company’s researchers are also developing technology that involves implanting a chip directly on the brain, which could allow people who are paralyzed by a stroke, an accident, or amyotrophic lateral sclerosis (ALS) to operate a computer, a smartphone, a wheelchair, or even lights and appliances, with their thoughts alone. For those whose condition has robbed them of speech, the chip could one day make it possible to translate thoughts into words and sentences and paragraphs on a screen. The technology could even translate those thoughts into spoken, computer-generated words—in the person’s own voice, if video or other recordings of them speaking before their illness were available, which the AI loaded into the computer could copy.
In this system, the implanted computer chip would not just sit on the brain, but become part of the brain. Using a technology Hodak calls the biohybrid model, the chip would be seeded with stem cells which would grow into the brain tissue, forging useful connections with neurons that govern thought, speech, creativity, and more.
“You can imagine making a chip with 100,000 electrodes that, when this grows into the brain, you could get a billion synapses,” Hodak says. “Right now you can get information into the brain very easily. Getting information out of the brain is limited. Imagine if you could get imagery or audio or imagination or memories out of the brain.” He says James Cameron’s Avatar movies are “a pretty good reference” for how biohybrid interfaces work. Paralyzed people would not, of course, inhabit new bodies as they do in the films, but they would gain some control over their worlds as if they were up and about.
Science Corp. is not remotely alone in pursuing this union of the computer and the brain—this wedding of cold silicon and warm carbon. According to the World Economic Forum, there are up to 680 companies worldwide at least dabbling in brain-computer interface (BCI) technology, making for a sector valued at $1.74 billion in 2022, and expected to grow to $6.2 billion by 2030. BCI today is what the personal computer was in the early 1980s—an infant technology that could grow in globe-shaking ways, with some of the companies talking about not just treating patients with ALS or other forms of paralysis, but also using the technology with firefighters, the military, and other first-responders, speeding reaction times and communication. BCI could even be used by the general public—or at least that part of the general public that wants to have mind-to-mind access to AI systems.
“People with brain implants will be able to interact with AI in ways that people without brain implants do not,” says Matt Angle, CEO and founder of the Austin-based BCI company Paradromics. “That is in some sense a superpower.”
The new science is causing not just a technological sensation, but also a cultural one, twanging a live wire in the popular mind. No sooner were the COVID vaccines released in 2020 than unfounded rumors swirled that they contained microchips that would be injected in the body—giving the government access to your thoughts. No sooner did reports go around that the U.S. and China were installing dashboard cameras and other equipment to detect signs of fatigue in long-haul truckers than the internet spun that up into stories about both countries using hardware that could read the drivers’ minds. It’s not for nothing that Apple TV’s Severance—the addictively twisty thriller about office workers who undergo microchip brain surgery to separate their work minds from their home minds—earned a staggering 27 Emmy nominations at the 2025 awards. The public reaction to developments in the BCI field is all of a piece with this—equal parts healthy fascination and troubling misinformation.
“Over the last 20 years, every time there was an advance in this technology, the principal investigators would get calls saying that someone—the government, their wives—had put a chip in them,” says Florian Solzbacher, the co-founder and chief science officer of Utah-based Blackrock Neurotech, a BCI company. “There’s a lack of training in critical thinking.” BCI, for better or worse, is here. The job now is for scientists to figure out how to use it—and for laypeople to figure out what to make of it.
The best known of the BCI companies—thanks to the ubiquitous presence and deep pockets of its founder, Elon Musk—is Neuralink, based in Fremont, Calif. Founded in 2016, the company has so far placed its implants in the brains of 12 people, hoping to allow them to operate a computer or smartphone with their thoughts. Neuralink is currently running a clinical program dubbed Prime, which is seeking to enroll patients 22 years old and up, who have quadriplegia and are willing to have a 1,024-electrode chip, about the size of a quarter, implanted for a study expected to last six years.
In January 2024, the company implanted its first chip, into the brain of Noland Arbaugh, a 29-year-old Yuma, Ariz., quadriplegia patient who lost movement below the shoulders in a diving accident. The implant allows him to control a cursor on a screen with only his thoughts—playing video games, surfing the web, and communicating with friends. Hodak was part of this groundbreaking work, as one of Neuralink’s founders and its president before leaving to launch Science.
There is, too, San Francisco–based Echo Technologies, led by University of California, San Francisco, neurosurgeon Dr. Edward Chang. In 2021, Chang and his colleagues published a paper in the New England Journal of Medicine reporting that they had developed a so-called neuroprosthesis allowing a paralyzed man who could not speak to generate words on a computer screen with nothing but his thoughts. In 2023, as reported in Nature, they improved the system to include computer voice synthesis along with the text, as well as a facial avatar that can display emotions and expressions as it speaks, reflecting the subject’s words. In 2024, as reported in Nature Biomedical Engineering, Echo upgraded the hardware to allow another patient, who was bilingual, to toggle between English and Spanish.
“Our system is fully wireless,” says Chang. “The onscreen avatar is designed to resemble the person who’s doing the speaking. But in reality it could be anything. It could even be an emoji if that’s what the person wanted.”
With the rise of AI in information processing it’s no surprise that it’s at play here too. BCI speech systems rely on so-called large language models that interpret speech and predict the next word or words—much as word–processing programs will suggest the word juice if you type out orange, or States if you type United.
“The things we’re decoding are not just single words but the probability of any single word,” says Chang. “We’ve been working to learn how the brain processes words, how the electrical activity of the brain gives rise to consonants and vowels, how they give rise to the planning of words.”
The system also recognizes the parts of the brain that control the lips, jaw, tongue, and larynx. By thinking about speaking, even people who have lost the ability activate these brain centers in ways that would form any given word. Think about saying ball and your brain would send a signal for you to press your lips together to pronounce the b and move your tongue to the back of your front teeth to pronounce the l. The computer recognizes these signals and helps convert them to words.
Elsewhere, Blackrock Neurotech has implanted over 50 people with brain chips, and boasts of amassing thousands of patient–days without adverse events. The most common of these events are infection of brain tissue at the site of the implant; malfunction of the implant, causing it to send spurious signals that would damage the brain; or fibrous encapsulation of the chip, as tissue grows around it, causing it to fail. With these risks avoided, Blackrock focuses on using its system to allow patients to operate computers and, as with Echo, speak via an on-screen avatar. Solzbacher describes one ALS patient whose disease had progressed to what is known as locked-in syndrome, in which the mind remains alert but with no way to communicate with the outside world. That patient underwent surgery to have a chip implanted and a computer voice created.
“He was able to talk with his 3-year-old daughter,” says Solzbacher. “That was the first time that happened in his daughter’s life and it’s quite powerful, actually.”
The matter of how a locked-in patient gives consent to the surgery is a tricky one. Typically, says Solzbacher, consent is given earlier in the course of the disease, before the subject slips into a completely locked-in state. Relatives may also be in possession of advance declarations the patient made while still able to communicate.
Blackrock has been at this work for a while. In 2014 it ran a clinical trial in which a subject named Ian Burkhart, who was paralyzed from the elbows down at age 19 when he was swimming off the Outer Banks of North Carolina and dived into a wave that pushed him into a sandbar, was implanted with a brain chip and then outfitted with electrodes on the skin of his forearm, hand, and elsewhere. Merely by thinking of moving his extremities he could activate the electrodes, which would cause the arm or hand to move as commanded, allowing him to grasp and hold objects and even play Guitar Hero. Burkhart felt a sense of triumph—and even vindication—at the results.
“For quite a few years I heard doctors saying, ‘Well, you’re never going to be able to move this, move that, do this, do that,’” he says. “And now I was able to.”
Brain-computer interface technology sometimes doesn’t even require scientists to bother the brain at all. Even minimal, lightly invasive brain surgery is still, well, brain surgery, and at New York City–based Synchron Inc. they’re able to avoid it. Instead, they thread a probe carrying a chip through the radial artery in the forearm or the femoral artery in the thigh up to the brain and deposit the chip in the main vein between the brain’s two motor cortexes. From there, says Kurt Haggstrom, Synchron’s chief commercial officer, “you can actually listen to the brain and understand it, without ever having to touch the brain itself.”
The first BCI surgery occurred in 1998, when neurologist Philip Kennedy implanted a chip in the brain of a man who suffered from locked-in syndrome caused by a brain-stem stroke. After intensive practice, the patient was able to move a cursor on a screen—a significant achievement, but a painstaking one. The limitations in the results were partly the result of the limitations of the chip, which was a four–channel model that was able to carry only minimal information.
“It was a very primitive device,” says Jamie Brannigan, a resident neurologist at Mount Sinai in New York and a BCI expert. “But it was the first example of an in-human brain–computer interface.”
Since then, a more powerful chip, the Utah array, has become the default device for the BCI field. The chip measures 4 mm by 4 mm and includes 100 needlelike probes, each measuring 1.5 mm, which penetrate brain tissue. It was first implanted in a human being in 2004, and has been the go-to chip for most BCI work since.
“The Utah array has a proven track record of safety, reliability, and longevity,” says Solzbacher.
Blackrock’s 50 implant surgeries certainly suggest that there’s evidence behind what it claims it can do with the chip, but the company’s competitors aren’t so certain. For starters, even at 4 mm by 4 mm, the Utah array would be too big and clumsy a hunk of hardware for Science to implant in the eye or Synchron to thread through a vein. And the 100 probes, while a not inconsiderable number, put a ceiling on how much data the system can carry.
“The thing about the Utah array is that it’s a 1990s device,” says Brannigan, “and if you were using a 1990s chip in your smartphone, you’d very quickly know about it.”
There is also the sort of controlled trauma inflicted on the brain when the 100-wire chip punches 100 tiny holes in its surface. At Paradromics, researchers have developed a chip with thinner wires than the Utah array, something that reduces, but does not eliminate, the damage done to brain tissue.
“There’s a fairly considerable amount of brain injury and cell loss with those technologies,” says Chang. “There is a term in the field called butcher ratio, and it refers to the number of cells killed for every one neuron you can record from. The more electrodes you put into the brain, the cumulative injury rises. The worst-case scenario is that a patient has some residual function, and this is lost as a result of the implantation.”
His company, Echo, sidesteps the problem, using not a chip with probes, but a thin film that sits on the brain without penetrating it. “The film is just laying safely on the brain surface monitoring signals from there,” says Chang.
It’s Hodak’s biohybrid model that would represent the real revolution in chip design, but the technology is not yet ready for human experimentation. In one section of the Science labs is a modified, tractor-trailer-size shipping container housing a small colony of cynomolgus monkeys. The animals have room to climb and jump and perch on a few branches—a big improvement over the tiny wire boxes in which they would have been forced to live their entire lives in the past. But they still don’t appear terribly happy.
“Don’t look them in the eye,” Hodak says. “They take that as a threat display.”
Happy or not, the monkeys will make their contribution to science. Last summer, the first of the animals was implanted with a biohybrid chip, and the company is now tracking its progress and seeing if the stem cells actually grow into the brain.
Hodak concedes that the biohybrid model poses perils. There is always a chance the stem cells could grow uncontrollably, crowding out native cells and damaging the brain. To prevent that, the system has a “kill switch,” in the form of an antiviral drug called ganciclovir that could be used off-label to attack the new cells and stop the growth process.
The hardware the BCI players are building might be impressive, but it’s very much in the beta stage—not remotely ready for release. The Prima system has given Alice Charton the ability to read the newspaper, but the glasses are wired to a 2-lb. plastic brick that houses the processing computer and the battery. It is difficult to carry around, especially for someone trying to navigate the street, and it tends to grow hot. On lab bench after lab bench in the Science headquarters, researchers are working on a second–generation Prima system in which the hardware currently in the brick will be miniaturized and housed in the glasses’ temple bars. But Prima 2.0 is not ready for release yet, so for now users are stuck with the brick.
Buckhart, whose Blackrock implant enabled him to move despite his paralysis, had the chip removed seven years after it was implanted. The system included a wire that ran from the implant to a small hole in his skull to which a cable was screwed when he was using the chip. Over time, the skin of his scalp would try to grow over the port, leading to repeated infections and causing him enough discomfort that he gave up on the system. He would have it re-implanted, he says, but only if it were wireless and required no port.
“I’m looking forward to getting another device,” Burkhart says.
He could be part of a group that may one day number in the millions—including able–bodied people who see BCI as a force multiplier for their natural abilities. Solzbacher envisions a lot of uses for BCI technology on the battlefield and among firefighters and other first responders, who could control the tools of their trades with their thoughts.
“There are performance parameters that can be made better and faster,” says Solzbacher. Performing a physical action like launching a weapon or calling for help takes time. “A signal goes out, and it has to go from intent and planning to premotor to motor execution to the spinal cord to the muscles until you push a button on a joystick. You lose relevant time. You could shortcut all of that. If you’re a firefighter or a soldier this could make the difference between coming home alive and unharmed or not.”
And none of that touches the benefits that could accrue to other people outfitted with BCI chips, who could then communicate and interact with AI systems. “As the devices become more powerful,” says Angle, “healthy people will want those abilities and be willing to undergo surgery to get them. The capabilities that will enable augmentation of natural human abilities are inseparable from those that restore function for persons with disabilities.”
For now the work goes on—slowly. Most BCI studies in the U.S. are conducted under the Food and Drug Administration’s (FDA) investigational device exemption, which permits developers to work with animal and human subjects before a device is approved. Planning for clinical trials, running the trials, writing up the results, and then waiting for permission to market the device can take five years. Still, most of the leaders of the BCI companies agree with the FDA’s go-slow way of doing things—at least for the public record.
“These are Class III medical devices, which means a permanent implant,” says Haggstrom. “You really want to make sure you develop a good safety profile while the device operates over time. After that, the FDA usually requires a 12-month follow-up study.”
Finally, there is the inevitable matter of what all this shiny new technology will cost. The companies aren’t at all ready to discuss marketing so nascent a product, but Hodak does venture a number—on the order of $100,000 to $200,000 for a Prima implant.
“Even though we would like this to be as low-cost as possible,” he says, “the reality is that this technology cost several hundred million dollars to develop and bring to market.”
BCI is now at a profound inflection point—a young science that is only now beginning to mature. The matters being sorted out in the lab and in the field are not just technical and medical. They are existential. Humanity has developed a lot of new technologies in the past 150 years—powered flight, automobiles, electric lights, radio, television, the telephone, motion pictures, and more. But there has always been an unbreachable barrier between them and us. The machines stood over there and we stood over here. Computers demolished that wall. They actively engage our eyes, our hands, our ears, our minds. With BCI, they are becoming part of our physical selves. In at least small ways, the machines are becoming more human and the humans, by definition, are becoming more machine. The benefits are real. So too are the questions they raise. □
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