LAUSR

BACKGROUND Current Perception Threshold (CPT) is a technique used for diagnostic purposes that applies sinusoidal currents transcutaneously at 5Hz, 250Hz and 2KHz to preferentially excite C, Aδ and Aβ afferent nerve fibres correspondingly. This fact may be interesting for evoking different electrotactile sensations for a wide variety of applications. METHODS Sensations evoked by 5Hz, 250Hz and 2KHz frequencies; sinusoidal, square, and 250μs-pulsed waveforms; and conventional and concentric electrode configurations were analysed in 19 healthy volunteers. Stimuli were applied in the dorsum of the hand in a double-blind manner and CPTs were defined based on participants' verbal feedback. After each stimulus participants filled in a form with sensation modality, irradiation, intensity, and emotion descriptors. RESULTS The frequency showed a significant effect on the four domains of evoked sensations and the waveform showed a significant effect on the modality domain. For most waveform and electrode configuration combinations, 5Hz evoked mostly a low-intensity prickling sensation; 250Hz mostly evoked an uncomfortable medium-intensity tingling sensation; and 2KHz mostly evoked a low-intensity tingling sensation. No thermal or noxious sensations were evoked. A significant interaction effect was only found between the frequency and the waveform factors. The electrode configuration did not show either a significant effect on the evoked sensations or an interaction effect with the frequency or waveform type. CONCLUSIONS Transcutaneous electrical stimulation may evoke different sensations at different frequencies due to the preferential activation of different fibre types. The results of these analysis could be used to enhance human-machine/computer-interaction systems based on electrotactile feedback.