HyVE: hybrid vibro-electrotactile stimulation for sensory feedback and substitution in rehabilitation.

Electro- or vibro-tactile stimulations were used in the past to provide sensory information in many different applications ranging from human manual control to prosthetics. The two modalities were used separately in the past, and we hypothesized that a hybrid vibro-electrotactile (HyVE) stimulation could provide two afferent streams that are independently perceived by a subject, although delivered in parallel and through the same skin location. We conducted psychophysical experiments where healthy subjects were asked to recognize the intensities of electroand vibro-tactile stimuli during hybrid and single modality stimulations. The results demonstrated that the subjects were able to discriminate the features of the two modalities within the hybrid stimulus, and that the cross-modality interaction was limited enough to allow better transmission of discrete information (messages) using hybrid versus singlemodality coding. The percentages of successful recognitions (mean ± standard deviation) for nine messages were 56 ± 11 % and 72 ± 8 % for two hybrid coding schemes, compared to 29 ±7 % for vibrotactile and 44 ± 4 % for electrotactile coding. The HyVE can be therefore an attractivesolution in numerous application for providing sensory feedbackin prostheses and rehabilitation, and it could be used to increase the resolution of a single variable or to simultaneously feedback two different variables.