Two people with paralysis in their hands were able to temporarily regain their sense of touch and feel the shape of objects, thanks to electrical brain stimulation. The approach could one day help people with spinal cord injuries to better carry out everyday activities by controlling a robotic arm that feels like their own.
There have been previous efforts to restore touch through brain stimulation, but they were . 鈥淭hese were very basic sensations of contact and no contact,鈥� says at the Chalmers University of Technology in Sweden. 鈥淏ut when you touch a surface, you feel the texture, the edges, the curvature. You feel the motion of your hand relative to the surface.鈥�
To evoke richer sensations, Valle and his colleagues worked with two people with spinal cord injuries that had led to partial paralysis, including the loss of most of their ability to move and feel with their hands. The researchers asked the pair to imagine wiggling their fingers and feeling sensations in them while scanning their brains with an MRI machine. Guided by which areas of their brains lit up during these exercises, the team then implanted dozens of tiny electrodes into corresponding regions.
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By using the implants to zap brain cells linked to hand movements and sensations, the researchers pinpointed signals that made the participants feel like they were holding a can, pen or ball. They also identified signals that mimicked the motion of objects across their fingers. 鈥淚t blew me away,鈥� says Scott Imbrie, one of the participants. He hadn鈥檛 felt objects so clearly for decades, he says.
To see if the approach could help with everyday tasks, the researchers then attached Imbrie鈥檚 electrodes to a robotic arm that held onto a steering wheel and got him to watch a virtual car travelling along a straight road.
They transmitted electrical signals into his brain to mimic sudden movements of the wheel against his hand to the left or right, then asked Imbrie to keep the car on track by counteracting these with his mind, transmitting his brain signals to the robotic arm.
Imbrie managed to keep the car on track 80 per cent of the time. He says it felt like the arm was an extension of himself. 鈥淚t was like, 鈥榦h my god, this arm is part of me鈥�.鈥� The team plans to carry out the same task with the second participant.
Valle hopes that the approach could one day help people with paralysis use robotic arms to carry out everyday activities, such as cooking and shopping. 鈥淔or a person with spinal cord injury, this could give a kick of independency,鈥� says at the Swiss Federal Institute of Technology in Lausanne. It could become a reality in just a few years, he says.
But the approach probably won鈥檛 be accessible to most people with paralysis. 鈥淵ou require a very good neurosurgeon to implant these things in the brain, and the cost will be in the thousands,鈥� says Micera.
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