Visual Feedback Control of a Rat Ankle Angle Using a Wirelessly Powered Two-Channel Neurostimulator

Abstract

Peripheral nerve disconnections cause severe muscle atrophy and consequently, paralysis of limbs. Reinnervation of denervated muscle by transplanting motor neurons and applying Functional Electrical Stimulation (FES) onto peripheral nerves is an important procedure for preventing irreversible degeneration of muscle tissues. After the reinnervation of denervated muscles, multiple peripheral nerves should be stimulated independently to control joint motion and reconstruct functional movements of limbs by the FES. In this study, a wirelessly powered two-channel neurostimulator was developed with the purpose of applying selective FES to two peripheral nerves—the peroneal nerve and the tibial nerve in a rat. The neurostimulator was designed in such a way that power could be supplied wirelessly, from a transmitter coil to a receiver coil. The receiver coil was connected, in turn, to the peroneal and tibial nerves in the rat. The receiver circuit had a low pass filter to allow detection of the frequency of the transmitter signal. The stimulation of the nerves was switched according to the frequency of the transmitter signal. Dorsal/plantar flexion of the rat ankle joint was selectively induced by the developed neurostimulator. The rat ankle joint angle was controlled by changing the stimulation electrode and the stimulation current, based on the Proportional Integral (PI) control method using a visual feedback control system. This study was aimed at controlling the leg motion by stimulating the peripheral nerves using the neurostimulator.

A Therapeutic Strategy for Lower Motor Neuron Disease and Injury Integrating Neural Stem Cell Transplantation and Functional Electrical Stimulation in a Rat Model

“…In previous studies, neurostimulators used in healthy rat limbs showed step responses of 200–250 ms [ 14 , 15 ]. The denervated muscle reinnervated by stem cell transplantation in the present study had a similar response, and there was little oscillation generation and good precision of control in the visual feedback control tracking of the randomly moving target, as shown in the Supplementary Video S1 .…”

“…However, the FES strategy for drop foot reported in the paper had limitations, namely: the risk of infection by wires, the difficulty of selective stimulation of nerves, the need for manual manipulation, the impossibility of complex movements, and the inability to modulate stimulation incrementally. To overcome these challenges, our researchers developed a wirelessly powered two-channel neurostimulator that modulates switching according to the frequency of the transmitted signal and the controlled angle of the naive ankle joint by changing the stimulation electrode and current using a visual feedback control system based on the proportional–integral (PI) control method [ 14 ].…”

A Wirelessly Powered 4-Channel Neurostimulator for Reconstructing Walking Trajectory

“…In this study, a wirelessly powered four-channel neurostimulator was developed to conduct FES for four nerves in a rat selectively to generate ankle and knee motions, as shown in Figure 1 : the tibial and peroneal nerves were related to ankle joint motion and the femoral nerve and branch of sciatic nerve connected to femoral biceps were related to knee joint motion. A magnetic resonance method [ 24 , 25 ] was employed to conduct wireless powering to the neurostimulator, which was developed based on our previous study [ 20 , 21 ].…”

“…In this study, we developed a four-channel wirelessly powered neurostimulator to control two joints in a rat: ankle and knee joints. The device we developed in this study has about 40 times higher resolution of stimulation current (from 0 to 0.4 mA with 0.1 A resolution) compared with our previous study [ 21 ], the stimulation frequency is controllable from 0 to 1 kHz, and duration is also controllable from 0 to 1 ms. The proposed method is a new strategy to reconstruct functional motion using their own hands or legs like robotic prostheses [ 22 , 23 ].…”

“…We proposed a multiple-channel neurostimulator to stimulate peripheral nerves with visual feedback control to achieve control of limb motion [ 20 ] as a new treatment strategy for patients of ALS and peripheral nerve injuries. In our previous study, a two-channel wirelessly powered neurostimulator was developed, and a rat ankle joint was controlled by FES to multiple peripheral nerves through the visual feedback control method [ 20 , 21 ]. In this study, we developed a four-channel wirelessly powered neurostimulator to control two joints in a rat: ankle and knee joints.…”