By quantitatively analyzing the effects of different configurations, it is possible to find the best configuration and further optimize neural prosthesis performances without changing system hardware and software. In this study, we investigated the effects of five types of electrode configurations on electromyography (EMG)-based recruitment characteristics by utilizing multi-contact electrode to stimulate toad sciatic nerves. Five characteristic parameters (maximum amplitude, threshold current, slope, 50% level, and dynamic range) are derived from fitting recruitment curves using Boltzmann equation and the latency is measured by a simple user-defined algorithm. Based on these parameters evaluation, it is found that (1) the longitudinal tripolar with lowest threshold current appears to be well suitable for application to extent battery life and potentially reduce the damage to tissues and electrodes, and (2) the transverse configurations with gentle slope and large dynamic range are fit for the muscle force fine control, but their practical application may be limited by needing a large stimulus current. Therefore, these findings can provide a useful reference for designing a novel electrode configuration to further optimizing control of neural prosthetic devices.
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