Your brain is amazingly adaptable. It can regulate your heart rate, have nightmares, remember a song you last heard decades ago from just a few notes and even pick up an entirely new language.
It can do all that because brains are plastic: able to rewire the pathways they use as they pick up new skills or respond to differences in the world around them. That neuroplasticity is the brain's way of keeping up with changes to the external environment or to the body itself. But soon our brains could face their biggest challenge: being connected to a computer through a brain-computer interface (BCI), something that could change how we view the world, our own bodies, and even the speed at which we can produce changes in the world.
Most invasive (that is, inside the skull) brain-computer interfaces involve putting electrodes onto the surface of the brain to pick up the electrical signals that pass through the tissue. Unsurprisingly, on a basic biological level, brains don't take well to having bits of silicon stuck on them. They form what's called fibrotic tissue -- a small scar around the electrode itself. While that may sound concerning, although BCI technology is still relatively novel, that physical scarring reaction of the brain isn't thought to cause any major disruption to the brain that users should be worried about.
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But other changes that happen in the brain with BCI use could be far more wide reaching, and fascinating, than a lump of hardened tissue.
Brains are generally good at changing: they adapt to new tools and new environments. When we learn how to pick up a pencil, for example, our brains expand our idea of ourselves and what we can do to incorporate the new skills that pencils can facilitate -- writing and drawing, for example. It's same for driving, for using a smartphone, using knitting needles or a propane torch -- as we pick up each new skill, our idea of what we can do in the world expands.
The difference between having a tool in your hand and having a brain-computer interface -- essentially just another tool, albeit an advanced one -- is that the BCI goes directly to the neurons that are helping you interact with the world, says Justin Sanchez, a tech fellow at the Battelle Memorial Institute. "So the potential for those neurons to be directly adapted for the brain computer interface is that much higher [than with other tools]… there is adaptation or plasticity of your neurons when you use a brain interface and that plasticity can change in a wide variety of ways depending upon who you are," he says.
Research published last year found that even the use of a non-invasive BCI (where brain signals are read by sensors worn on, rather than in, the head) for a short time can induce brain plasticity. The study, which asked people to imagine particular movements, found changes after just one hour of use.
The brain's ability to rewire itself in this way can come in particularly handy in people who've had damage to their nervous systems -- for example, in people who've had strokes or spinal cord injuries.
That plasticity is particularly pertinent for BCIs, as researchers are hoping to use the systems to help people with brain and spinal cord injuries to overcome paralysis of their limbs or a lost sense of touch in parts of their body. If you think of the nervous system as your local public transport network, a stroke acts like a major traffic jam -- nothing can get in or out. BCIs help those who've had strokes to find alternative routes around such blockages, so neural traffic can continue getting to where it needs to go.
"People can use this to recover in strokes; they find another wiring route that was the been there all along, but wasn't used. The idea is that the BCI can help you find that new connection much faster than you could with trial and error or with what we would consider the gold standard rehabilitation," says Justin Williams, professor in the Department of Biomedical Engineering at University of Wisconsin-Madison, who researches neural-interface technology.
This rewiring ability can also affect how different parts of our bodies plug into our brains. In the future, brain-computer interfaces could be used by people with limb paralysis to control robotic prostheses: a BCI could decode the neural signals from people who have a paralysed arm, for example, and use those signals to move a robotic equivalent.
With regular use of a BCI-controlled robotic limb, our brains' internal map of our bodies could be adjusted to accomodate the robot arm as much as if was a standard part of the body. There's also no reason not to think that if someone with two working flesh arms also used a BCI to control two (or more) robotic arms that their brain's map of their body wouldn't be redrawn to add in the two extra arms.
What's more, BCIs can also cause a change in how users come to see their bodies in other ways. "With the long-term use of a BCI prosthetic, actually, there's a point at which it becomes embodied. Because it's connected so intimately with your nervous system, the person using the BCI actually starts to consider it as part of their whole," says Williams.
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It's also worth noting that it won't be brains alone that will need to be plastic to accomodate BCI use: computers will have to learn to adapt along with humans.
"You have two adaptive controllers that are interacting. You have this very sophisticated and, at this point, poorly understood adaptive controller, which is the brain, and then you have this very clunky one, which is whatever we put on on the computer, and they've got to interact in an effective manner to produce the correct outputs and effective outputs. They really have to play off each other, they have to encourage each other, they have to enable each other," says Jonathan Wolpaw, director of the National Center for Adaptive Neurotechnologies.
Other effects of BCIs on the brain are likely to come to light later on, as the BCIs get put to new uses. DARPA, for example, is funding research into BCIs that could be used for warfare, where soldiers could control tanks or drones with their minds alone. Similarly, Facebook is involved in research into whether BCIs could be used to convert thoughts into electronic text. In both cases, BCIs could enable users to do away with UIs that need manual inputs -- such as entering commands or pushing buttons with their hands -- and instead use their thoughts to control systems.
That will mean a massive jump in the speed between an individual having a thought and that thought producing an action in the real world -- our ability to process information could be faster than has ever been possible.
"Computers can process signals a lot faster than a biological nervous system can, so there's the ability to scale time. You could potentially enact motion commands a lot faster than your nervous system necessarily would," says Sanchez.
"And again, that's an interesting aspect of how the brain can adapt to those kinds of situations. We are limited in our perception and interaction with the world by the fundamental speed of our nervous system. If you provide to the brain something that works faster, the brain can adapt to those kinds of situations and operate faster," he says.
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If that sounds wild to you, or if you're questioning your brain's ability to cope with faster-than-nerves inputs, you're not alone in wondering how technology can alter us. BCIs give us tools that work in ways that we've never had to learn before -- systems that don't need muscles to produce actions, and information that's conveyed directly to the brain, rather than through our eyes, ears and so on.
"The unique thing about BCIs is that they provide the brain with a new kind of output, which is output from brain signals. Instead of driving muscles, you go directly to a part of the brain, measure its activity in one way or another, and you convert that into some sort of action. The individual pieces of the brain that have evolved, as far as we understand, with the sole purpose of controlling muscles, they are now being turned into the outputs themselves," Wolpaw says.
"The basic question for BCIs is how well the brain can learn to do this new kind of thing that it wasn't designed for, and it wasn't evolved to do. And the answer up to the present is, it can sort of do it, but not all that well with our current methods," he added.
The human brain has coped with books and every new technology tool since fire and wheel -- BCIs are just likely to be another step on that adaptive journey. We know our brains can adapt, we'll have to wait to find out just how and how well.