Brain-computer interfaces (BCIs) are moving from experimental labs into real lives, with the number of people receiving implants more than doubling in just two years. Casey Harrell, a man with ALS who has been using a brain implant for nearly three years, demonstrates what's now possible: he can speak, work as a climate activist, surf the web, and read to his daughter, largely independently. His success story reflects a broader acceleration in BCI research and deployment that experts say is finally "taking off".

What Exactly Is a Brain-Computer Interface?

A brain-computer interface is a device that reads electrical signals directly from your brain and translates them into commands a computer can understand. Harrell's implant includes a set of electrodes embedded in his brain that detect the electrical activity associated with speech. These electrodes connect to two docking ports on top of his head that plug into a computer loaded with software trained to decode his brain signals into phonemes, the basic units of sound in speech. He can then use an eye gaze tracker to make corrections before the speech is played out loud.

Not all BCIs work the same way. Some are fully implanted and wireless, while others are less invasive and might involve placing electrodes on the surface of the brain or simply wearing a cap of electrodes. There's a fundamental trade-off: the closer the electrodes are to the neurons you want to record from, the better the signal quality, but the more invasive the surgery, the higher the risk of complications.

How Quickly Is BCI Research Expanding?

The growth in BCI trials has been dramatic. Between 1998 and the end of 2023, researchers identified 21 research groups that had implanted BCIs in a total of 67 volunteers across all trials. But since that 2024 analysis was published, the number of people with electrodes implanted in their brains has more than doubled. According to Mariska Vansteensel, a BCI researcher at University Medical Center Utrecht, the current estimate is around 150 people.

This expansion reflects both commercial and academic momentum. Neuralink, the BCI company founded by Elon Musk, announced in January that it has implanted its device in 21 people over the past two years. Other companies are also moving forward: Synchron is testing its devices in trials in North America and Australia, Shanghai-based Neuracle has been trialing a BCI since November 2024 and recently obtained approval for use outside clinical trials, and Precision Neuroscience is trialing a device that sits on the surface of the brain.

What Can BCIs Actually Do Right Now?

Current BCIs serve different purposes depending on the patient's condition and needs. Most BCIs in use today are implanted in people with spinal cord injuries, where they can help control external devices to restore mobility. However, Harrell's case shows that BCIs can also help people with ALS communicate and engage with the world.

The technology is improving rapidly. The BrainGate trial, a research effort that has been running for two decades, initially focused on "point-and-click" communication, allowing users to control a cursor and click with their brain activity. In recent years, the team has pivoted toward decoding speech. Harrell's device uses a voice clone, meaning the speech it produces is based on previous recordings of his own voice, which makes the output feel more personal and authentic.

"For him, the device is nothing short of revolutionary," Harrell told researchers. It has enabled him to maintain an income, reconnect with friends and family, and read to his daughter.

Casey Harrell, BCI trial participant

The UC Davis team that developed Harrell's implant has continuously refined and improved it. They've enhanced its accuracy and introduced new features including a privacy mode and a "profanity filter" that lets Harrell talk to his daughter without risking accidental swearing.

What Are the Key Players and Milestones in BCI Development?

The BCI landscape now includes multiple organizations pushing the technology forward:

• Neuralink: The company founded by Elon Musk has implanted its device in 21 people over the past two years and continues to expand its trial programs.
• BrainGate: An academic research effort running for two decades that has shifted from cursor control to speech decoding and continues to refine its approach with volunteers like Harrell.
• Synchron: Currently testing its BCI devices in trials across North America and Australia, offering an alternative approach to implantable technology.
• Neuracle: A Shanghai-based company that has been trialing its BCI since November 2024 and recently obtained approval to use the device outside of clinical trials, marking a significant regulatory milestone.
• Precision Neuroscience: Cofounded by a former co-creator of Neuralink, this company is trialing a less invasive device that sits on the surface of the brain rather than requiring deep implantation.

In a major regulatory development, China became the first country to approve a BCI for medical use, signaling growing confidence in the technology and opening new pathways for research and deployment.

What Challenges and Unknowns Remain?

Despite the progress, BCIs are still experimental, and significant questions remain. Scientists know even less about how BCIs might benefit people with conditions other than spinal cord injuries. In some cases where devices initially helped people with ALS, even those who were completely locked in, the BCIs eventually stopped working. The researchers don't really know why this happens.

"Since then, that number has increased a lot," noted Mariska Vansteensel about the expansion of BCI trials.

Mariska Vansteensel, BCI researcher at University Medical Center Utrecht

The only way scientists will answer these questions is through more research and the participation of volunteers willing to have electrodes implanted in their brains. Harrell himself has embraced this role, viewing his participation as a way to "pay it forward and do the scientific research" while also gaining personal benefit.

How to Stay Informed About BCI Research Progress

• Follow Academic Publications: Keep track of peer-reviewed research from institutions like UC Davis and University Medical Center Utrecht, which regularly publish findings on BCI efficacy and safety.
• Monitor Company Announcements: Major BCI companies like Neuralink, Synchron, and Neuracle regularly announce trial milestones, regulatory approvals, and participant numbers that signal progress in the field.
• Watch for Regulatory Approvals: Pay attention to government decisions on BCI medical use, as approvals like China's first-in-world authorization indicate growing confidence and may accelerate global development.
• Read Patient Stories: Case studies of BCI users like Casey Harrell provide real-world insights into how the technology works in practice and what benefits and challenges users actually experience.

The expansion of BCI trials represents a genuine inflection point in neurotechnology. With over 150 people now living with brain implants, the field is generating real-world data about what works, what doesn't, and where the technology can make the biggest difference. As researchers continue to refine these devices and expand trials to new patient populations, the next few years will be critical in determining whether BCIs can become a standard treatment for paralysis, locked-in syndrome, and other neurological conditions.