A man whose hand had been amputated has been able to feel the texture of different surfaces using a bionic fingertip, developed by scientists from a collection of European institutions. The device, which is described in a new study in the journal eLife, represents a major step forward within the field of prosthetic technologies, and could lead to the development of new artificial limbs that mimic the functionality of real body parts.
The mechanical fingertip consists of sensors that, when moved over a rough surface, generate electrical impulses that mimic the firing patterns of SA1 afferents, which are the sensory neurons found in human fingers.
Researchers connected the device to the amputee’s median nerve – which runs down the arm – using electrodes. In doing so, they enabled the signals generated by the bionic fingertip to be delivered to the subject’s brain via the median nerve, producing a sensory experience almost identical to the feeling of actually touching a rough surface.
After the experiment, the amputee participant Dennis Aabo Sørensen explained that “the stimulation felt almost like what I would feel with my hand,” adding that “I felt the texture sensations at the tip of the index finger of my phantom hand.”
Using the device, Sørensen was able to tell whether the surfaces were rough or smooth, with an accuracy rate of 96 percent.
The researchers also connected the fingertip to the median nerves of several non-amputees, and found that they too experienced sensory stimulation resembling the feeling of running their finger over a surface. Non-amputees could distinguish between rough and smooth textures 77 percent of the time.
To test whether the impulses generated by the device really did activate the same neuronal circuits that the SA1 afferents of the human hand do, researchers used electroencephalography (EEG) to monitor the brain activity of non-amputees when using the appliance and when actually touching a rough surface. EEG readings were highly similar in both scenarios, suggesting that the bionic fingertip genuinely does stimulate the brain in the same way as natural fingertips.
While more research is required before the technology can be incorporated into prosthetic limbs, the study authors are hopeful that devices such as theirs could be used to dramatically improve amputees’ quality of life.