Multi-Channel Electrotactile Stimulation System for Touch Substitution: A Case Study

Reconstructing the sense of touch in prosthetics is a long-standing research challenge. To this aim, the prosthesis can be supplied with sensory arrays to measure the tactile interaction with the environment. In addition, a reliable feedback system is required to code and transmit the measured somatosensory information to the residual limb. This paper presents a multichannel electrotactile stimulation interface. Two coding schemes (mixed and uniform coding) were tested to assess the ability of the subject to localize the stimulation (identify the active pad). The outcome measures were position recognition and frequency discrimination. Our preliminary results show high accuracies in discriminating different frequency levels, i.e., 80% for low-level frequencies and 87% for high-level frequencies. In addition, the mixed coding has substantially improved the spatial localization. These are important insights regarding the development of multichannel sensing and stimulation systems for feedback in prosthetics.