Abstract
The channel bridging, signal regenerating, andfunctional rebuilding of injured nerves is one of the mostimportant issues in life science research. In recent years, someprogresses in the research area have been made in repairinginjured nerves with microelectronic neural bridge. Based on theprevious work, this paper presents a neural signal detection andfunctional electrical stimulation (FES) driving system with usinghigh performance operational amplifiers, which has been realized.The experimental results show that the designed system meetsrequirements. In animal experiments, sciatic nerve signaldetection, regeneration and function rebuilding between two toadshave been accomplished successfully by using the designed system
.I. INTRODUCTION
The channel bridging, signal regenerating, andfunctional rebuilding of injured nerve is an issue inresearch of life sciences. Regarding for this, there are twobiological methods: 1) Implanting peripheral nerve fiberbundles. 2) Transplanting neural stem cells. The firstapproach is currently infeasible [1] and the other still remainsin exploration.In our recent research, we have proposed the concept of themicroelectronic neural bridge, which has been realized in theform of a combination of neural electrodes and electronicbridging circuits so as to replace the injured nerve [2]. Someencouraging progresses have been made in our laboratory[2-11].Our goal in the research is realization of implantablemicroelectronic modules and their functioning. In order toachieve this, we have designed integrated circuits [5-8], [10],and we have also built the regeneration modules withcommercial chips [4], [11]. Building modules reduce thedifficulty for us to test new circuits, which is useful referenceand guidance the chip design in the future. This paperdescribes the building modules and other related work. Based on previous research work [2-11], an improvedsystem for neural signal detecting and functional electricalstimulating (NSD-FES) is discussed in this paper. With thissystem, we have succeeded in detecting and processing neuralsignals, and function rebuilding between two toads’ sciaticnerves. In the following sections, the design of the circuits,testing result, and the animal experiment and results will begiven.II. SYSTEM DESIGNThe block diagram of NSD-FES is shown in Fig. 1. Thesystem contains three principal parts: neural electrode, neuralsignal detection circuits (NSD) and functional electricalstimulation (FES). The electrode detects neural spikes fromone side of nerve fiber bundles. After the process ofamplifying and filtering, the signals are transmitted into theFES, where a strong current suitable for nerve stimulation isgenerated. By stimulating the other side of the nerve fiberbundles, similar neural spikes are regenerated just as on thedetecting side. This is the process of signal regeneration. Adescription of each process part will be given as follows.Fig. 1 The block diagram of NSD-FES
A. Neural electrode
The NSD-FES can be implemented in some different kindsof neural regenerating system when matching different typesof neural electrode. In the animal experiment, the neural cuffelectrode produced by MicroProbes Company (USA) wasadopted for the neural signal detection and functionalstimulation. The reason of selecting cuff electrode is that thecuff electrodes can be easily attached to the sciatic nerve. Itprovides a good contact with the nerve even when the leg of atoad is moving. Therefore, unstable current drift andbreak-off of electrodes caused by the relative displacementbetween the nerve and the electrode can be eliminated.


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