Spatio-Temporal Properties Of Electrically Evoked Potentials Elicited By Multi-Channel Penetrative Stimulation In Opitc Nerve

As a potential way to restore vision for blind patients, the research of visual prosthesis based on electrical stimulation has received continued world-wide interest in the last two decades. Optic nerve stimulation with penetrating microelectrode array has been suggested as a possible and novel method for visual prosthesis. The purpose of this study was to investigate the feasibility and basic temporal and spatial responses of optic nerve stimulation with penetrating electrodes, using multi-channel recording electrode array implanted into the visual cortex area.Main contents of this research include: the construction of electrophysiological platform; the method to fabricate recording electrode arrays and their basic quality measurements; the threshold of current and charge density for optic nerve stimulation; the investigation of temporal properties of cortical response under different stimulating parameters; the investigation of spatial properties of cortical response under different stimulating electrode pairs; the evaluation of the optic nerve injury in different stages of orbital surgery by monitoring electroretinograms (ERGs) and visual evoked potentials (VEPs). The achievement and novelty of this research is as follows: constructed the animal electrophysiological experiment system and explored proper and effective methods; fabricated several types of recording electrode arrays on cortex, which can recorded multi-site cortical responses elicited by electrical stimulations on optic nerve; the threshold of current and charge density for optic nerve stimulation was 20.3±7.5μA and 37.8±13.9μC/cm2, correspondingly, which was much lower than that of the cuff electrodes around the optic nerve; the amplitude and latency of cortical responses can be changed by altering the intensity and phase of electrical stimulation; the spatial distributions of multi-channel electrically evoked potential (EEPs) in visual cortex demonstrated distinctively different properties under stimulation with two different orientations of the stimulating electrodes, moreover, the threshold of the electrode pair perpendicular to the optic nerve was much higher than that nearly parallel to the optic nerve.