A group of European researchers have recently created an artificial hand that can provide amputees with sensation. The project, called Lifehand 2, employed an artificial hand that allowed the user to feel the shape and texture of various objects. It has taken researchers many years to develop brain-controlled bionic limbs that offer the dexterity and sensory capabilities required to perform everyday functions, but, now, researchers have fitted such a device to a longstanding amputee.
With the aid of artificial sensors, and a series of electrodes implanted into the amputee’s arm, the research team developed an advanced prosthetic hand that can be used to provide the user with basic sensation, facilitating differentiation between an object’s size, weight, texture and stiffness with very little latency.
Published in Science Translational Medicine, the study represents a major milestone in the development of functional prosthetic limbs that incorporate “brain-machine interfaces.” Experimenters from Rome’s Gemelli Hospital, essentially, introduced a new circuit that allowed the bionic hand to communicate with the amputee’s brain. In a normal hand, sensory nerve endings transmit electrical impulses back to the brain, in response to a stimulus in the internal or external environment. Senior author Silvestro Micera, director of the Translational Neural Engineering Laboratory at Ecole polytechnique fédérale de Lausanne in Switzerland, recently explained that the bionic hand works using the same principles as a regular hand.
The team used the implantable electrodes to stimulate the median and ulnar nerves to afford the amputee with “near natural,” physiologically appropriate, sensory feedback; computer algorithms were used to refine the electrical signal, so that the sensory nerves could interpret them. The group reported that real-time decoding was possible, permitting the subject to perform different grasping tasks and successfully modulate the grasping force of the prosthetic hand, without the aid of visual or auditory feedback; all in all, the amputee consistently used, and perceived, three different grasping force levels. According to CNN, Micera recently discussed the remarkable functionality of the bionic hand:
“It is the first time that somebody is able to do it, relying on only sensory information provided by the prosthesis, by this neural stimulation.”
The experiment only lasted a duration of one week, but allowed the user to feel an assortment of objects, including bottles, mandarins, baseballs and cotton. The amputee involved in the study was Danish citizen Dennis Aabo Sorensen, who lost his left arm when a defective firework blew up. The 36-year-old was – for the first time in around 10 years – able to use the prosthetic hand to establish whether an object was soft or hard.
Unfortunately, the technology cannot be used outside of a laboratory setting, just yet, and further refinements need to be applied to the device before real-world use is possible. Sorensen’s bionic hand was attached to a computer for the entire duration of the experiment and, therefore, he is unable to use the hand when at home. In addition, Micera and colleagues need to prove that the implants will work safely and successfully over a sustained period.
Meanwhile, Aabo says he found the bionic hand to be “amazing,” and looked forward to the day when he could use a mobile version of the hand, permanently.
By James Fenner