High frequency block of selected axons using an implantable microstimulator.

Currently, the majority of neural stimulation studies are limited to acute animal experiments due to lack of suitable implantable microstimulation devices. As an initial step to observe the long-term effects of neural stimulation, a system consisting of an external wireless controller and an implantable dual-channel microcontroller-based microstimulator for tripolar high frequency blocking was developed. The system is not only small in size, and thus suitable for short-term implantation, but also has sufficient current output parameter ranges to meet the demand for high frequency blocking experiments. Using this implantable microstimulator, a series of experiments were conducted on New Zealand rabbit's tibial nerve, including frequency and amplitude selection in driving stimulus and blocking effect tests, which were designed to assess the feasibility and efficiency of the device via torque measurements. Our results showed that the implantable microstimulator system gave a satisfactory performance and could be utilized to achieve selective stimulation and blocking on various sizes of nerve fibers. Our implantable microstimulation system is not only a novel tool for neuromuscular control studies but could also provide a basis for developing various types of sophisticated neural prostheses.