Brain Computer Interfaces (BCI) Explained

Brain-computer interfaces (BCI) are devices that create a direct communication pathway between a brain’s electrical activity and an external output. Their sensors capture electrophysiological signals transmitted between the brain’s neurons and relay that information to an external source, like a computer or a robotic limb, which essentially lets a person turn their thoughts into actions.

These brain chips go over the scalp in a wearable device, get surgically placed under the scalp or even get implanted within brain tissue. The idea is that, the closer the chip is to the brain’s neural network, the more clear, or “high definition,” a signal can be interpreted.

What Are Brain-Computer Interfaces?

A brain-computer interface (BCI) is a device that lets the human brain communicate with and control external software or hardware, like a computer or robotic limb.

Once a cyborgian sci-fi trope that turned into reality at the dawn of the 2000s, brain-computer interfaces are now booming, with the $1.74 billion market expected to grow to $6.18 billion by the end of the decade. As healthtech research progresses and demand grows, startups are stepping up to pioneer the new wave of human-computer interaction.

Ramses Alcaide, CEO of neurotech startup Neurable, which develops non-invasive brain-computer interfaces in the form of headphones, sees potential for BCI-enhanced devices to become an everyday item for the average person.

“If we can make brain-computer interfaces accessible and seamless enough then they can be integrated into our daily lives, just as we use smartphones or laptops today,” Alcaide told Built In. “But in order to truly become a ubiquitous tool, they need to be comfortable, intuitive and reliable enough that people can use them without consciously thinking about them — similar to how we use a mouse or keyboard to interact with a computer.”

Today, the most common application of brain-computer interfaces involves moving a cursor by thought. And while most projects linger in an experimental phase, some have advanced to human trials.

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How Do Brain-Computer Interfaces Work?

While brain-computer interfaces differ in type and approach, they are all modeled after the electrophysiology of a brain’s neural network.

When we make a decision — or even think about making a decision — electrical chemical signals spark. This phenomenon is located in our nervous system; more specifically, in the gaps between neurons, known as synapses, as they communicate back and forth.

In order to capture this brain activity, BCIs place electrodes proximal to these conversations. These sensors detect voltages, measuring the frequency and intensity of each “spike” as they fire or potentially fire.

“We’re picking up the electrical chatter of the brain’s neurons communicating with each other.”

“It’s like a microphone; but in this case, we’re listening to electrical activity instead of sound,” said Craig Mermel, the president and chief product officer at Precision Neuroscience, a startup developing a semi-invasive, reversible neural implant. “We’re picking up the electrical chatter of the brain’s neurons communicating with each other.”

That information is then fed through local computer software, where it’s translated in a process known as neural decoding. This is where a variety of machine learning algorithms and other artificial intelligence agents take over, converting complex data sets collected from brain activity into a programmable understanding of what the brain’s intention might be.


Applications of Brain-Computer Interfaces

“The near-term goal [of brain-computer interfaces] is to give the abilities back to those who have lost them,” said Sumner Norman, a scientist at nonprofit startup Convergent Research and former chief brain-computer interface scientist at software firm AE Studio. “But in the long term, this tech is also intended to create a kind of tertiary cortex, or another level of the human brain function and an executive function that would allow us to be almost superhuman.”

These are some of the more common use cases of brain-computer interfaces:

Robotic Limbs and Wheelchairs

By supplying a real-time neural feedback loop that rewires the brain, BCIs are capable of restoring movement, mobility and autonomy for paralyzed and disabled patients, heightening their quality of life. In more chronic cases, robotic devices and limbs are integrated.


Wireless Headsets

Headsets are a way to deliver a non-invasive approach to brain-computer interfaces. Some boost productivity and enhance focus, as seen with Neurable’s Enten, while others restore motor functions to an individual’s upper extremities following a stroke, such as the IpsiHand system by Neurolutions Inc.



Non-verbal individuals, who may be stuck in a “locked in” state following a stroke or severe injury, can use eye movement for computer-augmented communication.


Smartphone and Smart-Home Device Interface

In several studies, users have exercised control of social networking apps, email administration, virtual assistants and instant message services sans motor skills. Dimming the lights or changing the channel on a TV are examples of how BCIs can be adapted in the home.



The Department of Defense has funded research to develop hands-free drones for military use. This would allow soldiers to telepathically control swarms of unmanned aerial vehicles.


Examples of Brain-Computer Interfaces

Neuralink’s Coin-sized Brainchip

The neurotechnology company, headed by Elon Musk, is developing a coin-sized surgical implant. In order to monitor brain activity as closely as possible, Neuralink’s device, the Link, uses micron-scale wires of electrodes that fan out into the brain. Its primary focus is to treat paralysis. In addition to a “Fitbit for your skull,” the startup is building an eight-foot robot to place the neural threads.


Neurable’s BCI-enhanced Headphones

The brain-computer interface startup is building software and hardware — in the form of headphones — that interpret brain signals to level up productivity. Its first pair, Enten, uses advanced data analysis and signal processing techniques to maximize a users’ peak focus periods throughout the day. The wearable, BCI-enhanced device auto mutes notifications, activates noise canceling and turns on ‘Do Not Disturb.’ It also tracks how different songs and genres impact a users’ focus, then recommends personalized playlists and suggests breaks.


Precision Neuroscience’s Electrode-packed Film

The neural platform is approaching brain-computer interface systems with a surgically implanted brain chip that’s minimally invasive and fully reversible. The Layer 7 Cortical Interface is a thin film of micro-electrodes, less than one millimeter in length and a fraction of a hair thick, that conforms to the brain’s cortex just under the skull without damaging any tissue. Precision’s tech wants to mainstream BCIs from small-scale research labs to medical facilities as a way to treat neurological diseases.


Synchron’s Endovascular Alloy Chip  

Backed by Bill Gates and Jeff Bezos, the bioelectronics medicine company is mapping the brain via blood vessels. Inserted through the jugular vein, the Stentrode is a neuroprosthesis placed in the superior sagittal sinus near the motor cortex. The eight-millimeter flexible alloy chip transmits neurological signals to a receiver unit implanted into the patient’s chest, which then translates thoughts into clicks and keystrokes on a computer or mobile device in real time. Synchron received approval from the U.S. Food and Drug Administration for human clinical trials in 2021, totaling four patients thus far, according to medical journal JAMA Network.


Blackrock Neurotech’s Mesh Lace

The neurotech platform has been testing its devices in humans since 2004 in its two decades of brain-computer interface development. Blackrock’s product portfolio has helped patients regain tactile function, movement of their own limbs and prosthetics as well as the ability to control digital devices solely from thought. Its latest project, Neuralace, is a flexible, hexagonal mesh patch — thinner than an eyelash — designed to conform to the fissures and sulci of the brain. Its large surface area can capture 10,000 neural channels, inching closer to whole-brain data capture.

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Benefits of Brain-Computer Interfaces

Restore Mobility and Motor Functions

Following a course of neurological rehabilitation, brain chips and wearables can give patients direct control over exoskeletons and robotic limbs. This is made possible by reading signals directly from the brain, bypassing the site of injury or disease — such as a severed spinal cord — muscular activity altogether.


‘Mindwriting’ for Non-verbal Individuals

With brain-computer interfaces, if you can think it, you can speak it. It’s just a matter of how fast neural decoding software can catch up.

A team from Stanford University found that its brain chip could hack 62 words per minute, which is on pace with natural conversation. The study featured a non-verbal patient who suffered amyotrophic lateral sclerosis and a pre-programmed vocabulary of 125,000 words, marking “a feasible path forward for using intracortical speech brain-computer interfaces to restore rapid communication to people with paralysis who can no longer speak.”


Treat Neurological Conditions

One study noted that individuals with ALS, cerebral palsy, brainstem stroke, spinal cord injuries, muscular dystrophies or chronic peripheral neuropathies may benefit from BCIs. Neural implants may be able to treat conditions or at least improve the quality of life for patients with chronic or terminal diagnoses.


Monitor Mental Health

Brain-computer interfaces may one day be able to ease psychiatric conditions, like bipolar disorder, obsessive compulsive disorder, depression and anxiety.

Using neurofeedback techniques, they can also help prevent more pedestrian conditions like burnout and fatigue by delivering targeted electrical stimulation to specific areas of the brain.

“It may not look as flashy, because someone in the demo just looks a little bit happier,” Norman, whose research at the California Institute of Technology as a postdoctoral fellow focused on this next generation of brain-computer interface tech. “But if you were offered a solution where I said, using a single device, I can treat any form of anxiety that you have, and also offer you sleep on demand and one hundred other applications that could make your life a little better than it was, I do think that quite a few people would adopt that technology.”


Cognitive Enhancement

Users can train their brains — memory, executive function and processing speed — to the biofeedback they receive from a neural implant in real-time. Similar to wearable tech and apps available today, users would be able to monitor their stats and self regulate accordingly.


Understanding the Brain

While much of the brain remains a mystery, BCIs are creating a direct channel to our thoughts — complete with a process to decode its language.

“Brain-computer interfaces can be used as a tool to understand how the brain works,” said Byron Yu, a professor of electrical and computer engineering and biomedical engineering at Carnegie Mellon University. The focus of his research group is studying how the brain learns. 

“If I give you a tennis racket and you practice with it, you will get better at playing tennis. Similarly, if I give you a brain-computer interface and you practice with it, you will get better at using the brain-computer interface,” he said. “We can then study what changes in the brain while you are learning to use the device. Our findings will eventually lead to methods to help people learn everyday skills more quickly and to a higher level of proficiency.”


Challenges of Brain-Computer Interfaces

Brain-computer interfaces have more than a half-century’s worth of research and several proof of concepts that passed human trials. So what’s the holdup?

The two largest hurdles keeping BCIs from widespread adoption have to do with regulatory approval and funding.


Regulatory Approval

Given that brain-computer interfaces are registered as a sort of medical device, they lie under the jurisdiction of the FDA. Regardless of the product, the institution’s primary concern is patient safety. 

The challenge is in the fact that BCIs currently exist in a league of their own. The devices themselves bring together a range of fields — implantable materials, safety-critical software, internet of things and wearable medical devices, to name a few — that are not yet standardized. There are no predicate devices.

“These are new categories of devices,” Precision Neuroscience’s Mermel said. “So, until there’s a device that gets cleared for market by the FDA, it’s an open question of what type of evidence you have to show to demonstrate that the benefit of a device outweighs the risk.”


Cost and Reimbursement 

If brain-computer interfaces make it to medical practice, who is going to pay for them? Or for the procedures? And what about the health-check follow ups, ongoing maintenance and upgrades that support the technology over time?

Determining whether the tab gets picked up by healthcare and insurance companies, government subsidies or patients out of pocket will greatly determine the devices’ level of accessibility to the public and who, based on socioeconomic status, are qualified for a tech-augmented quality of life.

“It’s important to prioritize the needs and perspectives of end-users, especially the most vulnerable, such as those with disabilities, and consider the potential ethical implications of these technologies,” Alcaide said. “We must ensure that these technologies do not perpetuate social biases or further exacerbate existing inequalities.”


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