Modulating the fidelity and spatial extent of electrotactile stimulation to elicit the embodiment of a virtual hand

Restoring tactile feedback in virtual reality can improve user experience and facilitate embodiment. Electrotactile stimulation is an attractive technology in this context because it is compact and allows for high-resolution spatially distributed stimulation. In this study, a 32-channel tactile glove worn on the fingertips was used to provide tactile sensations during a virtual version of a rubber hand illusion experiment. To assess the benefits of multichannel stimulation, we modulated the spatial extent and fidelity of feedback. Thirty-six participants performed the experiment in two conditions, where stimulation was delivered to a single finger or all fingers, and three tactile stimulation types within each condition: no tactile feedback, simple single-point stimulation, and complex sliding stimulation mimicking the brush movements. Following each trial, the participants answered a multi-item embodiment questionnaire and reported the proprioceptive drift. The results confirmed that modulating the spatial extent of stimulation, from a single finger to all fingers, was indeed a successful strategy. When stimulating all fingers, tactile feedback significantly improved all subjective measures compared to receiving no tactile stimulation. However, unexpectedly, the second strategy, that of modulating the fidelity of feedback, was not successful since there was no difference between the simple and complex tactile feedback in any of the measures. The results, therefore, imply that the effects of tactile feedback are better expressed in a more dynamic scenario (i.e., making/breaking contact and stimulating different body locations), while it should be investigated if further improvements of the complex feedback can make it more effective than the simple approach.