Vibrotactile Stimulation in the Upper-Arm for Restoring Individual Finger Sensations in Hand Prosthesis

Abstract

The implementation of a sensory feedback system is particularly important in upper limb prosthesis to improve closed-loop control and prosthesis acceptance. Restoring the touch sensations of individual fingers becomes critical in increasing the sense of embodiment of the artificial limb. Vibrotactile feedback appears as a feasible route to provide useful sensory feedback to prosthesis users. Most studies evaluate the stimulation of the forearm as a potential location of the sensory feedback system. However, it is also necessary to evaluate the stimulation of the upper arm to provide feedback to above-elbow amputees. In this work, the ability of 30 able-bodied subjects to discriminate vibrotactile stimulations in the biceps was evaluated. Particularly, experiments were conducted to evaluate their ability to discriminate different stimulation sites and different stimulation patterns. Stimulation sites were associated to tactile feedback from individual fingers of a virtual hand whereas simulation patterns were associated to potential grasping configurations of the hand. To compare the results, the same experiments were performed on the forearm. The results showed that subjects discriminated finger’s tactile feedback with about 94% average accuracy and grasping pattern feedback with about 85% average accuracy. The special acuity observed in the upper arm suggests that vibrotactile stimulation may also provide suitable feedback for restoring tactile sensation in above elbow amputees.