The ability to make lame or paralyzed people walk again was once the stuff of biblical stories, but not for much longer. Neurobiologist Dr. Miguel A. L. Nicolelis and his team at Duke University have found a way to do the unthinkable: give quadri- and paraplegics the ability to move their bodies using just their brain cells and a specially designed suit. If that sounds like futuristic science fiction, that’s because it is — the notion that you can move objects external to your body using only your mind seems fantastical to say the least. And yet, Nicolelis’ team has shown, with monkeys, that exactly that is possible.
Brain World: How did you find yourself wanting to learn more about the brain and its workings?
Miguel Nicolelis: My grandmother had a severe stroke when I was a child, and my grandfather had very serious Parkinson’s disease. Although that was obviously a painful experience, my desire to learn more about how brain circuits operate didn’t stem directly from that — it was my teacher Dr. César Timo-Iaria, at the University of São Paulo in Brazil, who inspired me in that direction. When I was a young student, I stumbled into a lecture he was preparing for a human physiology class. Using slides and classical music, he showed me how we had progressed from the beginning of the universe, with all its stars and galaxies, all the way to the complexity of the human brain. He believed that music and the scientific method were two of the greatest feats of the human mind — and, in part, that’s why I chose to dedicate my time to investigate and understand what I describe as, “symphonies composed by vast ensembles of brain cells.”
Once I began to look into brain circuitry, my team and I found that we were able to monitor 1,000 brain cells simultaneously. From there it was a logical step to consider training those brain cells to manipulate machinery. Or, in this case, to train a monkey to manipulate or control an avatar on a computer screen to do what was required in order to get a reward using only its brain cells.
BW: Several years ago, you and your team had successfully shown that monkeys can move an avatar on a computer screen using their brain cells. What was the next step in the process to using this knowledge to help para- and quadriplegics walk again?
MN: We were very excited about the breakthrough, but being able to move an object external to you isn’t enough. Even if the monkeys — or a human — were able to move a robotic arm, for example, to grab a glass, unless they can also receive sensory feedback from the object, they will be unable to function properly. Think about how you pick up a glass: you grasp it with your hand, but if you hold it too loose, it falls out of your hand and smashes on the floor. If you hold it too tight, you might crush the glass. This is why it was imperative that we find a way of sending sensory messages — regarding the texture, resistance, shape of an item—back to the brain as well.
When you think about what it feels like when you walk, your feet—or rather the nerves in your feet and the rest of your body — sense whether the surface is bumpy, whether there is an incline or decline. Without that feedback you would stumble and fall. It would be impossible to be able to walk properly in that way.
BW: And now the monkeys are able to receive such feedback from the objects they are touching with a virtual arm?
MN: Yes. The monkeys were able to learn how to receive tactile feedback from the object in just four sessions. We created a new sensory channel, a new sense, literally, that delivers to the sensory cortex so the animal can map up the information. It is almost as though the animal had a new arm — it adds this new limb to the brain as a representation. Our research also demonstrates that the brain creates active models of the self and the world, changing and adapting them according to its needs — the brain is not passive in this way, it’s active.
Our goal was to fool the brain that the avatar, in the case of the monkey studies, is part of the body module. We link the avatar to the central cortex and just by looking at the avatar hand, the brain — the sensory cortex — develops cells that respond to that avatar.
BW: How did you realize that this was possible?
MN: We recorded the activity of 300 cells in the brain and we saw that the brain develops a pattern of response. It’s similar to that for the animal’s real hand. If an animal, or a person, has an injury, say, where a limb or a finger is lost, the brain adapts to that new situation, being aware and changing its movements. The brain has to be active in this way, otherwise people or other animals would not be able to function unless their bodies were in perfect working order. Those missing a finger or a toe would not be able to write or walk, people with an amputated leg would not be able to use a prosthetic, and so on.