Phantom finger perception evoked with transcutaneous electrical stimulation for sensory feedback of prosthetic hand

This paper reports a pilot study to explore the plausibility of using the phenomenon of phantom finger perception (PFP) in amputees to develop sensory feedback for prosthetic hand. PFP can be aroused by touching a specific part of the skin in the stump area of amputees. We hypothesized that transcutaneous electrical stimulation (TES) can evoke the similar PFP in amputees with electrodes placed at the same skin area. We tested this hypothesis in subjects with distal amputation at the forearm above the wrist. The areas of PFP on the stump skin of amputee subjects were first identified and labeled by manually touching the skin. Electrical stimulation was then applied to the same area with surface electrode. The subjects reported that the corresponding finger was touched with electrical stimulation, and gradation of sensation with increased strength of stimulation current was perceived in a similar way as reported in normal subjects. Peripheral nerve sprouting into the receptors in stump skin after amputation is speculated as the neural mechanism of PFP. Preliminary results support the hypothesis that PFP evoked by TES can be utilized to establish a direct sensory feedback from the fingers of prosthetic hand to the amputee.