Comparison of codes for sensory feedback using electrocutaneous tracking

Ten electrocutaneous codes suitable for sensory feedback were systematically compared using a random tracking task. The representative sample of codes used single and multiple electrode displays, bipolar and monopolar electrocutaneous stimuli, and frequency, intensity, and spatial modulation. The experimental results from 2 preliminary studies using 4 subjects each, and a full scale study, using 21 subjects, suggested that electrocutaneous tracking was a reliable and sensitive indicator of a code's intrinsic effectiveness for transmitting information cutaneously. In addition, multiple electrode codes using spatial modulation were clearly and significantly superior to any single electrode codes examined. Single electrode codes using frequency modulation were superior to intensity modulation codes whether the pulse stimulus used was monopolar or bipolar. Although subjects rated bipolar stimulation as being slightly more comfortable than monopolar stimulation, they performed better when using monopolar stimulation. Furthermore, sensory adaptation to the monopolar stimulus was considerably less than to the bipolar stimulus. The most effective multiple electrode code was Seven Electrodes in a Linear Array on the Abdomen. The most effective single electrode code was the Low Pulse Rate Modulation Code, wherein the sensory information was embedded in pulse rates between 1 and 15 per second.