A 28-year-old American who has been paralyzed for more than a decade as a result of spinal cord injury is the first person to “feel” physical sensations through a prosthetic hand connected to his brain.
So sensitive is the sensation that he can even identify which mechanical finger is being touched.
A report from the Defence Advanced Research Project Agency (DARPA), run by the US military, says electrodes were placed in the patient’s sensory cortex – that part of the brain records tactile pressure – as well as the motor cortex that controls movement.
The advance shines a light on a future in which people living with paralyzed or missing limbs will not only be able to manipulate objects by sending signals from their brain to robotic devices, but also be able to sense precisely what those devices are touching.
“We’ve completed the circuit,” says DARPA program manager Justin Sanchez.
“Prosthetic limbs that can be controlled by thoughts are showing great promise, but without feedback from signals travelling back to the brain it can be difficult to achieve the level of control needed to perform precise movements. By wiring a sense of touch from a mechanical hand directly into the brain, this work shows the potential for seamless bio-technological restoration of near-natural function.”
Wires were run from the motor cortex to a mechanical hand developed by the Applied Physics Laboratory (APL) at Johns Hopkins University.
That gave the volunteer—whose identity is being withheld to protect his privacy—the capacity to control the hand’s movements with his thoughts, a feat achieved previously in another patient.
The hand contains sophisticated torque sensors that can detect when pressure is being applied to any of its fingers, and can convert those physical “sensations” into electrical signals.
The team used wires to route those signals to the volunteer’s sensory cortex in the patient’s brain allowing him to “feel” a sense of touch.
“At one point, instead of pressing one finger, the team decided to press two without telling him,” says Justin Sanchez.
“He responded in jest asking whether somebody was trying to play a trick on him. That is when we knew that the feelings he was perceiving through the robotic hand were near-natural.”
