Effects of the Stimulus Parameters on the Tactile Sensations Elicited by Single-Channel Transcutaneous Electrical Stimulation

This study was designed to answer the following three questions: (1) is it possible to elicit tactile stimulations by applying electrical stimulation to the skin?, (2) if so, how are the sensations affected by the stimulus parameters, pulse frequency, pulse amplitude (current), pulse width, polarity, and inter-electrode distance?, and (3) what is the relationship between the nerve afferents and the tactile sensations? The rectangular monophasic pulse train was applied to the subject's fingerpad for two types of experiments; amplitude/frequency modulations. In both types of experiments, we were able to elicit 4 major tactile sensations; tickling, pressure, low-frequency vibration, and high-frequency vibration. More than 95% of the subjects reported a consistent sensation order for each modulation. The narrow pulse width required a lower stimulation intensity to elicit a tactile sensation, and provided clearer sensations than the wide pulse width. The pulse polarity did not make a significant difference in the sensation quality. The long inter-electrode distance resulted in a lower stimulation intensity to elicit a tactile sensation than the short inter-electrode distance. Our observations suggested that the PC-like unit may be responsible for tickling, and that the FA1 nerve afferents for not only the low-frequency vibration but also the high-frequency vibration.