Ankle-Angle Estimation from Blind Source Separated Afferent Activity in the Sciatic Nerve for Closed-Loop Functional Neuromuscular Stimulation System

Abstract

Cuff electrode recording has been proposed as a solution to obtain robust feedback signals for closed-loop controlled functional neuromuscular stimulation (FNS) systems. However, single-channel cuff electrode recording requires several electrodes to obtain the feedback signal related to each muscle. In this study, we propose an ankle-angle estimation method in which recording is conducted from the proximal nerve trunk with a multichannel cuff electrode to minimize cuff electrode usage. In experiments, muscle afferent signals were recorded from a rabbit's proximal sciatic nerve trunk using a multichannel cuff electrode, and blind source separation and ankle-angle estimation were performed using fast independent component analysis (PP/FastICA) combined with dynamically driven recurrent neural network (DDRNN). The experimental results indicate that the proposed method has high ankle-angle estimation accuracy for both situations when the ankle motion is generated by position servo system or neuromuscular stimulation. Furthermore, the results confirm that the proposed method is applicable to closed-loop FNS systems to control limb motion.

Compact Optical Nerve Cuff Electrode for Simultaneous Neural Activity Monitoring and Optogenetic Stimulation of Peripheral Nerves

“…To obtain the pure neural signals, additional procedures for artifact removal were needed to use the neural signals contaminated by stimulation artifacts and to eliminate this interference because the amplitude of the stimulation artifacts was larger than that of the neural signals. One simple method for removing artifacts is the blanking process, which eliminates the stimulation artifacts that ground the neural signals during synchronized stimulation periods 17 , 20 . However, this process results in data loss during the stimulation periods.…”

“…For example, different initial joint positions and passive joint movements were estimated from muscle afferents recorded in the sciatic nerve 15 , 16 . The joint movements induced by electrical stimulation were also estimated from multichannel neural signals from the sciatic nerve 17 . With regard to the implantation feasibility, performing neural monitoring near the stimulation site is desirable to minimize invasiveness.…”

Separability of neural responses to standardised mechanical stimulation of limbs

“…Being able to use the MAV feature recorded on electrodes placed circumferentially around the nerve to differentiate between flexion and extension of the foot is perhaps unsurprising. During flexion the extensor muscles are stretched and during extension the flexor muscles are stretched, these are supplied by the tibial and peroneal nerves respectively 18 , 46 , 47 . At distal locations in the sciatic these branches remain spatially separated, resulting in the relative amplitude of the signal travelling along these branches appearing differently at electrodes placed circumferentially around the nerve.…”

“…Given this, spatial filters such as fast independent component analysis used by Song et al . 18 are likely to enhance separability of sensory information. Along the same vein, it is perhaps not surprising that increasing the longitudinal distance between two electrodes did not significantly increase the CCR, as the maximum distance we examined here was 1.5 mm.…”

Adaptive self-healing electronic epineurium for chronic bidirectional neural interfaces

“…In vivo electrical stimulation. An electrical stimulator (AM 2200, AM-system) with a programmed pulse generator, which was developed in our previous report 49 , was used to induce the biphasic current pulse on the sciatic nerve. The biphasic pulse was set to a 0.25 ms pulse width and different repetition stimulation pulse periods (5,10,20,50, and 100 Hz).…”