Vibrotactile sensory substitution in multi-fingered hand prostheses: evaluation studies.

This paper presents a vibrotactile sensory substitution system that could be used to deliver sensory feedback to transradial amputees wearing a myoelectric hand prosthesis. The novelty is an architecture that allows simultaneous variation of both amplitude and frequency using low-cost components and traditional techniques. The small dimension of the system allows to place it on different target points of the residual limb of an amputee (e.g. corresponding to phantom fingers). Experiments to evaluate the human capability to discriminate differently modulated stimulations and stimulation sites were carried out on healthy volunteers. Subjects were able to properly discriminate the different force amplitudes exerted by the device at different fixed frequencies. The effect of amplitude on the frequency discrimination was also studied and for most subjects it was easier to discriminate a lower frequency when its amplitude was lower than the amplitude of the reference signal. The distance of the stimulation sites for an optimal discrimination was also identified.