A brain implant that allows monkeys to move an avatar’s arm and feel objects in a virtual world has been demonstrated for the first time.
The animals used the device to control the arm by thought alone, and feel the texture of the objects it touched through electrical signals sent directly to their brains.
Researchers built the system as part of a major effort to help paralysed people regain the use of their arms and legs, feeling the objects they touch and the ground they walk on.
Without any sensation of touch, it would be easy for people to crush or drop objects they were trying to grasp, or misjudge the terrain underfoot and stumble, the scientists said.
Miguel Nicolelis, who led the research team at Duke University in North Carolina, said the technology was a milestone in his group’s bid to restore natural movement and fine control to paralysed people.
Nicolelis is working with colleagues at the Technical University in Munich to build a whole-body “exoskeleton” that can move people’s paralysed limbs in response to brain activity picked up by the implant.
“The patient will be able to use their brain to control their movement, but they could also get sensations back from their legs, arms and hands,” Nicolelis told the Guardian.
“We are looking to have a demonstration of this in time for the World Cup in 2014. When the Brazilian team walks on to the field, we want them accompanied by two quadriplegic teenagers who will walk on to the pitch and kick the ball using this technology.”
Nicolelis, who was born in São Paulo, the largest city in Brazil, said the challenge was “like the Brazilian moonshot”.
While a prototype exoskeleton might be more conspicuous than most patients would like, it will be quiet and made of lightweight materials. “Even the first generation is not going to be like Robocop,” Nicolelis said.
Writing in the journal Nature, Nicolelis describes a series of experiments in which monkeys learned to perform tasks on a computer in exchange for a reward, in this case a sip of fruit juice.
In the first round of experiments, the monkeys used a joystick to move a virtual arm on the computer screen in front of them. The screen displayed three identical images, each a circle within a circle. As the virtual hand moved over each, the joystick vibrated to convey one of three different “textures”. Using trial and error, the monkeys worked out that they received some juice when they placed their virtual hand in the centre of a circle with a certain texture.
In the second round of experiments, the monkeys switched over to the brain implant. This time, they moved the virtual arm by thoughts, which were picked up by fine wires inserted into the motor cortex region of their brains. The electrical activity of between 50 and 200 brain cells controlled the arm’s movements.
When the monkeys moved the virtual arm onto a circle, they experienced a sensation of texture from tiny electrical pulses sent directly to thousands of neurons in part of the brain called the primary tactile cortex.
The more time the monkeys spent with the implant, the more they appeared to view the virtual arm as a natural part of their body. “They got better and better at the task over time. By measuring how long they spent on each circle, you could see they were really focused on finding the right texture,” Nicolelis said.
Nicolelis calls the device a brain-machine-brain interface, because it translates brain activity into movement while sending information on texture back into the brain.
“The remarkable success with nonhuman primates is what makes us believe that humans could accomplish the same task much more easily in the near future,” Nicolelis said. “We hope that in the next few years this technology could help to restore a more autonomous life to many patients who are currently locked in without being able to move or experience any tactile sensation of the surrounding world.”