Temporal Response Properties Of Electrically Evoked Potentials Elicited By Penetrative Optic Nerve Stimulation

Vision is necessary for human to get information form the world. It is reported that visual information accounts for more than 70% of the total information human gets from the outside world. However, over 180 million people are visually impaired, including 45 million blind. China has the largest population of blind in the world; about 5 million Chinese people are blind. Therefore, study on visual prosthesis is in an urge by the whole society. A lot of research groups have been making efforts to develop visual prosthesis and some progress has been made.Visual prosthesis can be sorted to 3 types - visual cortex prosthesis, retinal prosthesis and optic nerve prosthesis, based on the different implanting position of stimulating electrodes along the visual pathway. All of these visual prosthesis employ electrodes to stimulate neural tissue of the vision system, and artificially generate phosphenes in the visual cortex. Therefore, to study the cortical response properties evoked by electrical stimulation is useful to learn the response properties and can provide experimental foundation for designing appropriate stimulus parameters.This paper focuses on the study of temporal response properties of electrically evoked potentials elicited by penetrative optic nerve stimulation, providing useful experimental data for designing stimulus parameters of the optic nerve prosthesis.Main contents of this paper include: 1. to determine animal models, investigate the optic nerve structure and implanting position for optic nerve stimulating electrodes; 2. to design stimulus parameters, fabricate electrodes for stimulation and recording and program software for electrophysiological experimental platform; 3. to carry on plenty of intraorbital penetrative optic nerve stimulation experiments, examine different temporal response properties of electrically evoked potentials elicited by different penetrative optic nerve stimulation, including variable stimulus amplitudes, pulse durations, frequencies and waveforms; 4. to analyze the stimulated optic nerves histologically and assess effects by exposure surgery and electrical stimulation of the optic nerve; 5. to obtain results of threshold and temporal response properties by experimental data analysis.The novelties of this paper are investigating temporal response properties of electrically evoked potentials elicited by penetrative optic nerve stimulation systematically, presenting fitting stimulus parameters for optic nerve stimulation, providing reliable experimental data for designing optic nerve micro-stimulator and stimulating electrodes.The results suggest that for the optic nerve stimulation, the short-duration (<0.5ms) symmetrical cathode-first biphasic pulses of current with low frequencies (1-2Hz) are more efficacious in eliciting electrophysiological responses in the visual cortex than other stimulation waveforms. The stimulus parameters maybe adopted by micro-stimulator for the optic nerve prosthesis.