Abstract
Multi-pad electrotactile stimulation can be used to provide tactile feedback in different applications. The electrotactile interface needs to be calibrated before each use, which entails adjusting the intensity to obtain clear sensations while allowing the subjects to differentiate between active pads. The present study investigated how the stimulation intensity affects the localization of sensations using a multi-pad electrode placed on a fingertip and proximal phalange. First, the sensation, localization, smearing and discomfort thresholds were determined in 11 subjects. Then, the same subjects performed a spatial discrimination test across a range of stimulation intensities. The results have shown that all thresholds were significantly different, while there was no difference in the threshold values between the pads and phalanges. Despite the subjective feeling of spreading of sensations, the success rates in spatial discrimination were not significantly different across the tested stimulation intensities. However, the performance was better for distal compared to proximal phalange. Presented results indicate that spatial discrimination is robust to changes in the stimulation intensity. Considering the lack of significant difference in the thresholds between the pads, these results imply that more coarse adjustment of stimulation amplitude (faster calibration) might be enough for practical applications of a multi-pad electrotactile interface.
Highlights
Electrotactile systems deliver low-intensity electrical currents to the surface of the skin, which depolarizes skin afferents and produces tactile sensations [1]
The present study systematically investigated the interaction between the stimulation intensity and the subject’s ability to localize the stimuli delivered using a multi-pad electrotactile interface
The interquartile range (IQR) was higher for all thresholds obtained on the proximal phalanx suggesting that inter-subject variability was higher for this segment
Summary
Electrotactile systems deliver low-intensity electrical currents to the surface of the skin, which depolarizes skin afferents and produces tactile sensations [1]. Favorable physical characteristics (low power consumption, simple fabrication, fast response) combined with the possibility of modulating multiple stimulation parameters (e.g., pulse width, amplitude, frequency, and location) independently and simultaneously, allow the designing of compact and high-resolution electrotactile displays. Such displays, based on multi-pad electrode technology, can be leveraged to successfully deliver high-fidelity information on multiple variables of interest in an intuitive manner, as recently exemplified in the context of the restoration of proprioceptive and grasping force feedback in myoelectric prostheses [19,20,21,22,23]. This takes time, especially when using a multi-channel interface, as the calibration needs to be performed for each channel individually
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