Perceptual attributes of cutaneous electrical stimulation to provide sensory information for prosthetic limb

The future development of artificial limb is to provide sensory feedback for amputee users. Cutaneous electrical stimulation is a convenient and energy efficient way to produce substituted sensory information. In this paper, we present the results of psychophysical experiments of electrotactile stimulation in normal human subjects. The purposes of these experiments are: (1) to identify the suitable electrode position in upper limb, and (2) to investigate the perceptual levels of sensation with cutaneous electrical stimulation that could be detected in human. We recruited 18 healthy subjects, in all experiments. 16 of them participated in the first set of psychophysical experiments, and 6 of them participated in the second set of experiments. In the first set of experiments, four positions of reference electrode relative to the stimulation electrode in the upper arm were tested. The results showed that positions opposite or 10 cm apart from the stimulation electrode required lower stimulation currents that evoked the similar level of sensation. In the second set of experiments with the reference electrode placed opposite to the stimulation electrode, a fine gradation of sensation was obtained by modulating stimulation current amplitude, pulse width and frequency. The results indicated that 15 levels of sensation could be detected by health subjects. These results are valuable in guiding further experiments on amputees and for future development of intelligent artificial limb.