Perception thresholds and qualitative perceptions for electrocutaneous stimulation

Abstract

Our long-term goal is the development of a wearable warning system that uses electrocutaneous stimulation. To find appropriate stimulation parameters and electrode configurations, we investigate perception amplitude thresholds and qualitative perceptions of electrocutaneous stimulation for varying pulse widths, electrode sizes, and electrode positions. The upper right arm was stimulated in 81 healthy volunteers with biphasic rectangular current pulses varying between 20 and $$2000\,\upmu \hbox {s}$$ 2000 μ s . We determined perception, attention, and intolerance thresholds and the corresponding qualitative perceptions for 8 electrode pairs distributed around the upper arm. For a pulse width of $$150\,\upmu \hbox {s}$$ 150 μ s , we find median values of 3.5, 6.9, and 13.8 mA for perception, attention, and intolerance thresholds, respectively. All thresholds decrease with increasing pulse width. Lateral electrode positions have higher intolerance thresholds than medial electrode positions, but perception and attention threshold are not significantly different across electrode positions. Electrode size between $$15 \times 15\,\hbox {mm}^{2}$$ 15 × 15 mm 2 and $$40\times 40\,\hbox {mm}^{2}$$ 40 × 40 mm 2 has no significant influence on the thresholds. Knocking is the prevailing perception for perception and attention thresholds while mostly muscle twitching, pinching, and stinging are reported at the intolerance threshold. Biphasic stimulation pulse widths between $$150\,\upmu \hbox {s}$$ 150 μ s and $$250\,\upmu \hbox {s}$$ 250 μ s are suitable for electric warning wearables. Within the given practical limits at the upper arm, electrode size, inter-electrode distance, and electrode position are flexible parameters of electric warning wearables. Our investigations provide the basis for electric warning wearables.

Perception of amplitude, pulse intervals, and location of electrocutaneous stimulation

“…The experimental setup was identical to the one in our previous publication 7 . Here, we give a brief overview, for details please see 7 .…”

“…The experimental setup was identical to the one in our previous publication 7 . Here, we give a brief overview, for details please see 7 . We use an in-house implemented program written in LabVIEW 2017 (National Instruments, Austin, TX, USA) to control a constant current stimulator DS5 (Digitimer Ltd, Letchworth Garden City, UK) via a PC and a multiplexer D188 (Digitimer Ltd, Letchworth Garden City, UK), which activates one of its 8 output channels and thereby delivers the stimulus to one of the desired eight electrode pairs.…”

“…Moreover, we observed that the volunteers perceived the location of the stimulus partly at single electrode positions and partly between and beyond electrode positions. These thresholds were consecutively investigated in a larger study group comprising 81 volunteers 7 . Further, the influence of pulse width, electrode size, and position was investigated in that study.…”

“…Knocking is the prevailing perception for perception and attention thresholds while mostly muscle twitching, pinching, and stinging are reported at the intolerance threshold. Biphasic stimulation pulse widths between 150 µs and 250 µs are suitable for electric warning wearables 7 .…”

“…In this study, we report on the suitability of varying amplitude, frequency, and location for encoding warning information for the same 81 participants 7 .…”