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Show 7 college of engineering We are continuing work on a visual neuroprosthetic to be implanted into the visual cortex to restore sight. Currently, we have implanted Utah Electrode Arrays, which are 10x10 arrays of microelectrodes, into the visual cortex of a Macaque. The arrays are used for stimulating and recording from cortical neurons. Neurons in the visual cortex are sensitive to electrical stimuli, and stimulating these neurons causes the subject to see points of light on their visual field, called phosphenes. With patterned stimulation, phos-phenes might convey information about images the same way as pixels. The goal of our project is not to create a fully functioning device, but to provide psychophysics data about stimulating cortical neurons. Our implanted Macaque is trained for electric threshold tasks. The task consists of showing a dot on a computer monitor and having the monkey report if he saw it. By interleaving the photic trials with variable current electrical stimulation, we can compute the threshold current required to produce a phosphene. When the monkey was first implanted, he was able to detect phosphenes when a single electrode was stimulated. Over time, he lost this ability, and we have had to stimulate groups of nine electrodes instead. We are currently training a new monkey to track the dependence of electrode number with time. Our results show that there is a spatial dependence of electrical threshold across the array, meaning that the amount of current needed for the monkey to detect a phosphene changes depending on which nine electrodes are stimulated. These results will be verified with the new monkey. A CORTICAL APPROACH TO VISUAL NEUROPROSTHETICS Elias Bagley (Bradley Greger) Department of Bioengineering University of Utah UNDERGRADUATE RESEARCH ABSTRACTS Bradley Greger Elias Bagley |
