Neuromorphic transcutaneous electrical nerve stimulation (nTENS) induces efficient tactile-related cortical networks in forearm amputees

Conventional transcutaneous electrical nerve stimulation (cTENS), which uses a modulated square waveform as stimuli, has been generally used in testing and eliciting artificial tactile perception in forearm amputees. However, a novel neuromorphic TENS (nTENS) model based on neural signals has been largely ignored. In this study, we further explore the effect of nTENS patterns to elicit tactile perception in forearm amputees. Four forearm amputees were recruited to test discriminate tactile perception elicited by different TENS patterns with electroencephalography (EEG) recording at the following four stimulated sites: the index finger and the little finger on both phantom and real sides. Finally, we compared the results of cortical networks in six frequency bands at different stimulated sites between forearm amputees and able-bodied subjects. Behavioral results suggested that nTENS patterns required a lower electric charge at each stimulated site than cTENS patterns. And forearm amputees required a higher intensity in each TENS pattern than able-bodied subjects. Moreover, amputees showed a lower clustering coefficient (aCP), global efficiency (aEG), local efficiency (aEL), and a longer path length (aLP) than able-bodied subjects in all six frequency bands when stimulation was accessed. Specifically, the SMU pattern showed a higher functional network efficiency in real fingers than at phantom sites in theta, alpha, and high gamma bands. This study highlighted the characteristics of nTENS patterns in eliciting tactile perception among forearm amputees, which provided insights into evaluating the neural mechanism of tactile information processing in forearm amputees and building tactile perceptual systems for sensory rehabilitation.