Interaction of Perceived Frequency and Intensity in Fingertip Electrotactile Stimulation: Dissimilarity Ratings and Multidimensional Scaling.

Sensations elicited by electrical stimulation of touch are multidimensional, varying in perceived intensity and quality in response to changes in stimulus current or waveform timing. This paper manipulated both current and frequency, while volunteer participants estimated the dissimilarity of all non-identical pairs of 16 stimulus conditions. Multidimensional scaling analysis revealed that a model having two perceptual dimensions was adequate in representing the electrotactile (electrocutaneous) sensations. The two dimensions were identified as perceptual frequency and intensity, and were strongly correlated with the two stimulus variables, frequency and current, although not in a 1:1 correspondence. Perception of frequency differences increased monotonically with stimulus intensity, which is consistent with other human sensory systems, such as hearing and vision. Our results are consistent with previously-reported research using a different methodology and cutaneous locus. Congruence across different methods and laboratories suggests similar underlying perceptual mechanisms.