Microelectronic neural bridging of toad nerves to restore leg function

Abstract

The present study used a microelectronic neural bridge comprised of electrode arrays for neural signal detection, functional electrical stimulation, and a microelectronic circuit including signal amplifying, processing, and functional electrical stimulation to bridge two separate nerves, and to restore the lost function of one nerve. The left leg of one spinal toad was subjected to external mechanical stimulation and functional electrical stimulation driving. The function of the left leg of one spinal toad was regenerated to the corresponding leg of another spinal toad using a microelectronic neural bridge. Oscilloscope tracings showed that the electromyographic signals from controlled spinal toads were generated by neural signals that controlled the spinal toad, and there was a delay between signals. This study demonstrates that microelectronic neural bridging can be used to restore neural function between different injured nerves.

Keywords: basic research; coherence function; electromyographic signal; grants-supported paper; microelectronic neural bridge; nerve injury; neural regeneration; neuroregeneration; photographs-containing paper; spinal reflex arc; spinal toad.

Figure 1

Neural signals of leg function restoration between the sciatic nerves of different toads using mechanical stimulation. Y-axis represents signal intensity (μV). (A) When pushing or pulling the leg of the source spinal toad, a series of neural signals was generated. These signals were detected by hooked electrodes, amplified, and processed by the microelectronic neural bridge, and transmitted to the sciatic nerve of the controlled spinal toad where a neural signal was regenerated and caused the leg to move similar to that of the leg of the source toad. (B) Expanded waveforms of three signals in (A), in a short period. (A, B) The waveform of the original neural signal (upper), and the electromyographic (EMG) signals of source and controlled spinal toads (middle, lower). (C) The middle waveform of (C) shows the denoised signal from the upper waveform, which is the middle signal of (B) from the denoised signal. Pattern recognition was completed according to the amplitude and time course of the spikes. Raster graphics were obtained and are shown in the lower graph of (C). In this manner, neural spikes were extracted. The waveform of the original neural signal (upper), the denoised version (middle), and the raster graphics (lower) are shown.

Figure 2

Neural signals of leg function restoration between the sciatic nerves of different toads using chemical stimulation. Y-axis represents signal intensity (μV). (A) Waveforms ①–④ represent the signal detected from the sciatic nerve of the source spinal toad, the electromyographic (EMG) signal detected from the left leg of the source spinal toad, the signal detected from the sciatic nerve of the controlled spinal toad, and the EMG signal detected from the left leg of the controlled spinal toad, respectively. Dashed line frame shows the corresponding signals. (B) Expanded waveforms of signals ③ and ④ in a short period. Arrows show corresponding signals.

Figure 3

Block diagram of the microelectronic neural bridge. FES: Functional electrical stimulation.

Figure 4

Printed circuit board of the 4-channel microelectronic neural bridge comprised of operational amplifier integrated circuits and discrete devices.

Figure 5

Experimental schema of signal regeneration between the sciatic nerves of two toads. Waveforms ①–④ represent the signal detected from the sciatic nerve of the source spinal toad, the electromyographic (EMG) signal detected from the left leg of the source spinal toad, the signal detected from the sciatic nerve of the controlled spinal toad, and the EMG signal detected from the left leg of the controlled spinal toad, respectively.