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K.-J. Wu, M.-J. Sun, P.-J. Cao, X.-Y. Chai, Q. Ren; Electrical Evoked Potential Elicited by Optic Nerve Stimulation With Penetrating Electrode Array in Rabbits. Invest. Ophthalmol. Vis. Sci. 2007;48(13):669.
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The purpose of this study is to investigate the electrical evoked potentials (EEPs) elicited by direct electrical stimulation of the intra-orbital optic nerve with penetrating single electrode and multi-electrode array.
Albino rabbits were used as animal model. The visual evoked potential (VEP) was evaluated before the electrical stimulation as a control study. Then orbital surgery was performed to expose the optic nerve. First, electrical stimulation was applied with a single stimulating tungsten electrode (Φ=50µm) penetrated into the optic nerve 1mm distant from the eye globe. EEPs elicited in the visual cortex was investigated. Then, an array of four electrodes was implanted into the optic nerve with simultaneous current stimulation applied by all electrodes of the array and EEPs were recorded with variable stimulus’ intensities. Electrical stimulations of different temporal-spatial patterns were applied to the penetrating electrode array at the optical nerve. The EEPs elicited by these different stimulating protocols were studied and compared. Histological examination of the optic nerve was taken after the acute experiments to judge the injury of the surgery and the electrical stimulation.
EEPs could be recorded by biphasic current stimulation of the optic nerve using penetrating single electrode and multi-electrode array. Threshold charge density was 35.9µC/cm2 with our electrode, which was lower than the safe limit value for chronic implantation and the previously reported optic nerve prosthesis by surface electrode array. As changing the temporal-spatial patterns of stimulation, different EEPs were elicited. Amplitude of P1 (the first positive peak of EEP) decreased when optic nerve was stimulated spatially with sequential form proximal to distal position along the optic nerve; with spacing between stimulating and return electrodes increasing, amplitude of P1 became lower and the implicit time was shortened; implicit time of P1 elicited by multi-pulses per chain of single electrode were longer than that by sequential stimulation of 4 electrodes of the array with the same stimulating parameters. Histological evaluation revealed no serious damage of surgery and electrical stimulation.
Electrical evoked potentials were recorded by our penetrating single electrode and multi-electrode array at the optic nerve. Our experiments demonstrate that different stimulation patterns can elicit disciplinarian responses at the visual cortex.
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