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When you think of hacking, the first thing that comes to mind might be someone typing out a bunch of code in a basement somewhere as they try to access your bank account. But not all hacking is bad — and the goal isn’t always to break into a computer system. There’s a whole field of research dedicated to using what are known as brain-computer interfaces, or BCIs, to hack the nervous system.

BCIs let you control prosthetics using only your mind and actually feel what the prosthetic feels. And someday, we might even be able to use the technology to help with paralysis. Modern prosthetics have come a long way: they’re much lighter than they used to be, for example, and they come in designs that range from natural-looking to super-sci-fi.

But there are still plenty of challenges. Many prosthetic limbs don’t move, and the ones that do generally rely on vocal commands from the user, or interact with other nerves and muscles. Plus, most of these prosthetics don’t send information back to the brain about what the limb is doing, the way a biological limb would.

This often restricts what you can do with the prosthetic, like move fingers in a natural way. It also means you can’t tell whether, for example, the glass you’re holding is slipping or breaking. That’s where BCIs come in.

When you think about it, there are lots of parallels between electronics and your nervous system. In general, your whole nervous system is like a transceiver — the term used in electronics to refer to something that both transmits and receives information. In your body, this communication drives movements, or changes states, like from awake to sleeping.

Your nervous system receives information from all of your senses, but for prosthetics, touch is usually the most important. Touch tells your brain if a part of your body hot or cold, if it’s tense or relaxed, and helps you keep track of where it’s located relative to the rest of you. And scientists can access this touch information because the brain is, conveniently, highly organized.

For example, the motor and somatosensory cortices control movement and process touch, and are arranged by body part. Although if you map out how much of the brain is dedicated to each body part, it’s hilariously out of proportion. But because these sections of the brain are so organized, researchers can use BCIs to tap into the touch channels and listen in, or even send a signal of their own.

Because electronics and your nervous system are more than just similar in terms of their functions — they’re also compatible with each other. They both use electrical currents to pass along information. The neurons that make up your nervous system send information electrochemically, by moving charged particles, or ions, across a membrane.

These ions create electrical currents, which can trigger an electrical signal called an action potential to fire and send the signal along to the next neuron in the network. Action potentials make your nervous system even more computer-like because they’re binary, meaning there are only two options. Like the 1s and 0s used by computers, action potentials can either fire, or not fire.

With sensors known as EEGs, researchers can pick up these types of electrical signals happening just beneath the skull. They can also put electrodes directly into the brain to record the signals going to and from the body. With tools like these, they can listen to the parts of the brain that control a biological arm and determine which neurons are firing when.

The firing patterns make up a neural code, and there are unique patterns for when, say, a person reaches for a glass of water, or is sitting quietly. Then, all researchers have to do is translate this neural code into a language that computers can use to control robotic limbs. With advances in artificial intelligence, like complex layers of processing nodes that can help with signal classification, prosthetics that use BCIs are already out there.

Engineers help users train the BCI to move their limb with their minds, providing more natural control. And with recent developments in artificial nerves, prosthetic limbs can now also provide feedback to the nervous system. Synthetic touch nerves, for example, have sensors that detect pressure and vibration.

In the fingertips of a prosthetic hand, they can help the user detect texture and grip strength, which means you’re a lot less likely to have that glass-dropping problem. The technology is already practical enough to be used by some people, who either have electrodes implanted in their brains or wear an EEG device. But there’s a lot of work left to be done.

For one thing, BCIs are still incredibly expensive, which means fewer people have access to them. They also don’t usually have great battery life. And remember, this is hacking at its roots, so digital security is something we’ll need to take into account as BCIs become more advanced and more popular.

In the meantime, researchers are looking to expand the uses of BCIs to things like wheelchairs, military exoskeletons, smartwatches, and cars. They’re also developing versions that might be able to help people with paralysis or movement disorders like cerebral palsy. That’s more complicated than with prosthetics, because the BCI has to do more than just learn what the brain is trying to tell the limb — it has to properly communicate it to the muscles.

But despite the challenges, BCIs are already changing the lives of people all over the world. We’re seeing the beginnings of a totally new type of union between human and machine. Using BCIs to improve prosthetics may be a way to use hacking for good, but usually, hacking is not good!

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