Restoration of Tactile Sensation for Prosthetic Users by Non-Invasive Electrical Stimulation and Assessment with EEG*

Restoration of tactile sensation for prosthetic users represents a key challenge in the field of bionic robots. Previous studies have demonstrated that transcutaneous electrical nerve stimulation (TENS) is a useful non-invasive approach to induce intuitive sensory feedback for limb amputees. This work aims to investigate the influence of stimulation parameters on tactile sensation evoking, and evaluate the sensory feedback performance from the aspect of cerebral cortex activities. We recruited one transradial amputee and three able-bodied participants, studied the threshold and type of sensation evoking by adjusting the stimulation amplitude, pulse width and frequency, and compared the brain’s response behaviors between the amputee and the able-bodied by analyzing the event-related potential (ERP) and brain electrical activity mapping (BEAM). Experimental results show that the evoking threshold is determined by both pulse width and amplitude, and in general the able-bodied have higher thresholds than the amputee. For both types of participants, tactile sensations of vibration and pressure can be evoked at stimulation frequencies of 10 and 100 Hz, respectively. There is an obvious difference in cerebral cortex activation between the amputee and the able-bodied, where the former has a lower tactile acuity than the latter. ERP shows the able-bodied have stronger N1 activation, whereas the amputee has stronger N2 activation, and BEAM indicates distinct spatial distribution patterns of cortical areas associated with N1 and N2. This work may contribute to understanding the neural mechanism underlying the TENS-evoked sensory feedback and provide a technique support for advanced prostheses and bionic robots.