Evaluation of Human Proprioceptive Matching Ability in Discrete Grasping Motions: Implications for the Sensory Reconstruction of Prosthetic Hand

The lost motor functions of an upper-limb amputee can be restored by means of multi-DOF myoelectric prostheses. However, the somatosensory (tactile and proprioceptive) feedback from a commercial prosthetic hand to the user is still missing, especially the proprioceptive feedback (PF). An object grasping or manipulation actually are organized in phases characterized by muscle synergy and delimited by means of discrete sensory "events". Inspired by the Discrete Event-driven Sensory feedback Control (DESC) policy, we delimited the continuous grasping motion into discrete wrist and finger motions to evaluate human proprioceptive matching ability. In current study, four kinds of typical hand motions (radial flexion, ulnar flexion, wrist flexion and lateral prehension) were passively generated by stimulating respective forearm dominated muscles via non-invasive electrical stimulation (ES) and then actively reappeared with the ipsilateral hands on eight able-bodied subjects. Under two types of matching conditions (PF and PF+ visual feedback (VF)), the human proprioceptive matching ability were evaluated and analyzed. Based on this, a feasible method (interface) used for encoding the grasping movement from fingers of the prosthetic hand to an upper-limb amputee was proposed.