Artificial sensibility based on the use of piezoresistive sensors. Preliminary observations

Piezoresistive sensors, applied to the fingertips of non-sensate fingers, were used for the detection of touch and pressure in four patients with recent median nerve repairs, and in one patient using a myoelectric prosthesis. The signals from the sensors, produced by the tactile stimuli, were processed and transposed as electrical stimuli to sensate skin of the ipsi- or contralateral arm by the use of skin electrodes. With this setup the test subjects could rapidly learn to differentiate between tactile stimuli applied to different fingers, thereby regaining spatial resolution in the hand. All five patients rapidly improved their ability to regulate the power of pinch grip without the help of vision. The patient with a hand prosthesis rapidly learned to discriminate between four different levels of pressure, applied to the thumb by four different Semmes--Weinstein monofilaments (75, 125, 280 and 450 g). These results indicate that the system is of potential value for patients lacking sensibility or using prostheses.