| Eye was called psychical window, it is one of the most important sense organs for people. According to sanitation office's statistic, there were 5,000,000 blind people live in China and it accounted for 18% in the world. And according to basic forecast, there will be 75,000,000 blind people in the world until 2020. It is obvious that blindness menaced human badly and caused big trouble to people's life. There were many reasons that can make people blind, any section's damage on visual system can make people lose vision. Through electrical stimulation on nerve cell of any section in visual system can make blind people feel light, which was called phosphene, it can transfer limited but important visual information to help blind people resume basic vision. According to the different position of electrical stimulation, artificial visual prosthesis includes three methods: visual cortical prosthesis, retinal prosthesis and optic nerve prosthesis, the visual cortical prosthesis was fit for many kinds of blind people and had the biggest ability to resume the most patient. Under the support of national'863'program (No. 2007AA04Z324), this project took the leader in doing research on key technology about epidural visual cortical prosthesis based on artificial visual prosthesis theory, it designed new electrical stimulation equipment and did basic research about epidural electrical stimulation mode and effect. This project had important scientific meaning and practical value.Under the research background of this project, this paper designed an electrical stimulation signal generator based on virtual instrument. This generator was designed by LabVIEW software, and used PCI-6014, CompactDAQ-9172 and 9265 module to output voltage and current signal. These signals'parameters can be adjusted easily, which included wave shape, amplitude, frequency, pulse width, stimulation time and stimulation mode. Wave shapes included: monophasic pulse, biphasic pulse, sine wave, triangle wave, sawtooth wave and index wave; Output range of voltage was±10V, output range of current was 0~20mA, and the precision was 10-9; Frequency range was 0.01～5000HZ; Pulse width (duty cycle) range was 0%～100%; Stimulation time length included pulse train length and inter-train interval length; Stimulation mode included one signal stimulation and two signals alternate stimulation.This paper did basic research about epidural experiment method based on this generator, and built animal experiment platform about electrical stimulation research. The basic experiment method was: putting two chips out of the left and right dura of 17 visual area in cat, the electrical stimulation signal generator was connected to one chip and gave electrical stimulation, the multi-path physical signal record system was connected to another chip and recorded electrically evoked potential (EEP) on the another side of cortex at the same time. This paper did basic research about epidural electrical stimulation's effect on EEP, contrasted EEP wave shape and stability under single pulse or pulse train stimulation, studied different stimulation parameters'effect (amplitude, pulse width and frequency). Besides, this paper did pilot study about epidural electrical stimulation security, the experiment method was: during the same period and under the same stimulation parameters, giving three mouse different electrical stimulation that the inter stimulation time was different, then sliced up and colorated nerve cells to observe the denaturalization condition, and evaluated inter stimulation time's effect and the security of high frequency stimulation.Through analyses of these experiment results, some conclusions can be get, which were: (1)The system can get positive direction evoked potential under single pulse stimulation, the potential's amplitude and delitescence was different with stimulation condition, but the characteristic of repetition wasn't good; (2)The system can get complex wave under pulse train stimulation, the wave's amplitude will increase with stimulation signal's amplitude, frequency or pulse width, and the delitescence was steady. The experiment results were repetitious; (3)During the same experiment period and under the same stimulation parameters, the nerve cell which got the shorter inter stimulation time will got worse damage.The research results proved the feasibility and dependability about building electrical stimulation equipment and experiment platform based on virtual instrument. The basic experiment results about stimulation mode and effect were got, and these results established experiment basis for further research of this project. |
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