Robotic touch shifts perception of embodiment to a prosthesis in targeted reinnervation amputees

TLDR

Existing prosthetic limbs lack cutaneous feedback, yet tactile input is essential for intuitive control and is linked to body self‑identification. The study hypothesizes that physiologically relevant cutaneous touch feedback will help amputees incorporate an artificial limb into their self‑image. A robotic touch interface coupled to a prosthetic hand, using pressure sensors and a robotic stimulator to deliver signals to surgically redirected cutaneous nerves, was tested on two targeted reinnervation amputees in Rubber Hand Illusion–style experiments. Subjective and objective measures showed that physiologically appropriate cutaneous feedback produced a vivid embodiment illusion, shifting perception toward integrating the prosthesis as an extended body part.

Abstract

Existing prosthetic limbs do not provide amputees with cutaneous feedback. Tactile feedback is essential to intuitive control of a prosthetic limb and it is now clear that the sense of body self-identification is also linked to cutaneous touch. Here we have created an artificial sense of touch for a prosthetic limb by coupling a pressure sensor on the hand through a robotic stimulator to surgically redirected cutaneous sensory nerves (targeted reinnervation) that once served the lost limb. We hypothesize that providing physiologically relevant cutaneous touch feedback may help an amputee incorporate an artificial limb into his or her self image. To investigate this we used a robotic touch interface coupled with a prosthetic limb and tested it with two targeted reinnervation amputees in a series of experiments fashioned after the Rubber Hand Illusion. Results from both subjective (self-reported) and objective (physiological) measures of embodiment (questionnaires, psychophysical temporal order judgements and residual limb temperature measurements) indicate that returning physiologically appropriate cutaneous feedback from a prosthetic limb drives a perceptual shift towards embodiment of the device for these amputees. Measurements provide evidence that the illusion created is vivid. We suggest that this may help amputees to more effectively incorporate an artificial limb into their self image, providing the possibility that a prosthesis becomes not only a tool, but also an integrated body part.