Two perceptual dimensions result from manipulating electrotactile current and frequency

Electrotactile (electrocutaneous) stimulation produces controlled, localized touch sensations at the location of a small stimulation electrode by passing a small electric current through the skin. The electric field thus generated in subcutaneous tissue directly excites the afferent nerve fibers responsible for touch sensations. The electrotactile sensation is multidimensional, varying in perceived intensity (as well as less-well-defined qualitative aspects) in response to changes in stimulus current or waveform structure or timing. We specifically investigated the perceptual dimensions resulting from manipulating stimulus current and frequency (4 levels each, full factorial) using paired-comparison dissimilarity ratings. Multidimensional scaling analysis revealed that a model using two perceptual dimensions accounted for 96 % of the overall variance in the electrotactile sensations, and that these two dimensions were strongly correlated with the two stimulus variables.