Electrically-Elicited Tactile Sensation for Different Modulation Types, Polarities and Waveforms of Stimulation Pulse Trains

This study was designed to investigate how the electrically-elicited tactile sensation is affected by different types of electrical stimulation in terms of the sensory activation threshold and sensation specificity. The experiments were conducted on 49 healthy subjects varying 1) the modulation type (pulse amplitude modulation and pulse width modulation), 2) the polarity (anodic and cathodic), and 3) the waveform (monophasic and biphasic). Our findings include that I) the sensation became adapted to the constant stimulation, 2) the modulation type and the polarity of the pulse train did not make a significant difference in the activation threshold, 3) the cathodic pulse train with the pulse amplitude modulation was more successful in activating Meissner's corpuscle than the anodic and the biphasic pulse train, 4) selective activation of Merkel disk was the most successful with the biphasic pulse train, 5) the activation threshold values showed a poor inter-individual consistency, but a strong intra-individual consistency 6) most of the subjects reported that the tickling sensation was localized, but that the pressure/vibration sensation was diffused. The results suggested that our stimulation protocol, though not perfect, can be applied to elicit three tactile sensations, tickling, pressure and vibration.