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PR Troyk; Implantation of Intracortical Electrodes in Macaque V1 . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3930.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To develop a primate animal model for studying the implementation of an intracortical visual prosthesis. Methods:192, 35-micron iridium wire electrodes were prepared for implantation in a primate V1. The electrodes were physically configured in sixteen 8-electrode arrays and 64 single electrodes. Laser-ablation of the paralyene-coated shanks produced a mixture of exposed surface areas of 200 and 500 sq. microns. Tips were coated with activated iridium oxide to enhance charge capacity. The surgery was planned in a series of meetings spanning 1 year. Presurgical CT imaging allowed for the fabrication of plastic models of the animals skull and brain. Customized connector housing, fitted to the curvature of the animals skull contained 24 Omnetics nano-connectors. The surgical procedure took 8.5 hours in which 152 electrodes were implanted. In the 4 months, following surgery, the electrodes were physically and functionally mapped. Results:114 of the implanted electrodes were electrically accessible. This number was expected based upon known defects in the hardware prior to, and during the, surgery. No electrodes were "lost" following surgery. For 60-70 electrodes spatial mapping was accomplished using an automatic recording system. 1-degree visual fields were measured using an averaging system over 15,000 trials. A retinotopic map was constructed using a combination of published primate maps, and the measured visual field information. Recordings from the electrodes were stable over at least a 4-month period. Recording is ongoing, with the emphasis shifting to orientation mapping. The mapping will be used to establish reward criteria for behavioral studies. These behavioral studies, consisting of memory saccade tasks, will be used to train the animal to used electrically invoked visual percepts as a replacement for visual stimuli. Conclusion:: It appears that an animal model for studying stimulation strategies for an intracortical visual prosthesis is feasible. Our ongoing studies are directed at understanding how an artificial interface to the cortex might be used to exploit the natural V1 tuning so that a cortical visual prosthesis could be implanted into a human.
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