Artifact-free sensory nerve signals obtained from cuff electrodes during functional electrical stimulation of nearby muscles

Restoration of the voluntary use of paralyzed limbs using functional neuromuscular stimulation (FNS) is limited by complex muscle properties and unpredictable load behaviors; closed-loop control of FNS would improve performance but requires reliable sensory feedback modalities. Sensory nerve signals recorded by cuff electrodes provide accurate information about forces acting on the skin in anesthetized animals; however, nerve cuff signals are very small (approximately 10 μV), and during FNS they become contaminated with large stimulation artifacts and synchronous EMG potentials from nearby muscles. The authors show in this study that it is possible to record neural signals from the cat tibial nerve without interference from distributed stimulation of four calf muscles surrounding the recording electrode by use of high-pass filtering and synchronized bin-integration. Nerve signals sampled in this way retained all the information about footpad contact force that was normally obtained in the absence of muscle stimulation. The authors propose that this approach has wide applicability for rehabilitation of paralyzed people with neural prostheses