Avi Caspi1, Michael P Barry2, Uday K Patel2, Michelle Armenta Salas3, Jessy D Dorn2, Arup Roy2, Soroush Niketeghad4, Robert J Greenberg5, Nader Pouratian6. 1. Jerusalem College of Technology, Jerusalem, 9372115, Israel; Second Sight Medical Products, Inc., Sylmar, CA, 91342, USA; Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, 21287, USA. Electronic address: avi.caspi@jct.ac.il. 2. Second Sight Medical Products, Inc., Sylmar, CA, 91342, USA. 3. Second Sight Medical Products, Inc., Sylmar, CA, 91342, USA; Department of Neurosurgery, University of California, Los Angeles, CA, 90095, USA. 4. Department of Bioengineering, University of California, Los Angeles, CA, 90095, USA. 5. Alfred Mann Foundation, Valencia, CA, 91355, USA. 6. Department of Neurological Surgery, UT Southwestern Medical Center, Dallas, TX, 75390, USA.
Abstract
BACKGROUND: Restoring sight for the blind using electrical stimulation of the visual pathways is feasible but demands an understanding of the spatial mapping of the visual world at the site of targeted stimulation, whether in the retina, thalamus, or cortex. While a visual cortex stimulator can bypass the eye and create visual percepts, there is an inherent dissociation between this stimulation and eye movements. It is unknown whether and how robustly the brain maintains the oculomotor circuitry in patients with bare- or no-light perception. OBJECTIVE: To critically and quantitatively evaluate the effect of eye movements have on phosphene locations elicited by cortical stimulation that bypasses the eyes in order to restore sight in blind subjects. METHODS: The NeuroPace Responsive Neurostimulator (RNS) and the Orion visual cortical prosthesis devices were used to electrically stimulate the visual cortex of blind subjects with bare or no light perception. Eye positions were recorded synchronized with stimulation and the location of the percepts were measured using a handheld marker. RESULTS: The locations of cortical stimulation-evoked percepts are shifted based on the eye position at the time of stimulation. Measured responses can be remapped based on measured eye positions to determine the retinotopic locations associated with the implanted electrodes, with remapped responses having variance limited by pointing error. CONCLUSIONS: Eye movements dominate the perceived location of cortical stimulation-evoked phosphenes, even after years of blindness. By accounting for eye positions, we can mimic retinal mapping as in natural sight.
BACKGROUND: Restoring sight for the blind using electrical stimulation of the visual pathways is feasible but demands an understanding of the spatial mapping of the visual world at the site of targeted stimulation, whether in the retina, thalamus, or cortex. While a visual cortex stimulator can bypass the eye and create visual percepts, there is an inherent dissociation between this stimulation and eye movements. It is unknown whether and how robustly the brain maintains the oculomotor circuitry in patients with bare- or no-light perception. OBJECTIVE: To critically and quantitatively evaluate the effect of eye movements have on phosphene locations elicited by cortical stimulation that bypasses the eyes in order to restore sight in blind subjects. METHODS: The NeuroPace Responsive Neurostimulator (RNS) and the Orion visual cortical prosthesis devices were used to electrically stimulate the visual cortex of blind subjects with bare or no light perception. Eye positions were recorded synchronized with stimulation and the location of the percepts were measured using a handheld marker. RESULTS: The locations of cortical stimulation-evoked percepts are shifted based on the eye position at the time of stimulation. Measured responses can be remapped based on measured eye positions to determine the retinotopic locations associated with the implanted electrodes, with remapped responses having variance limited by pointing error. CONCLUSIONS: Eye movements dominate the perceived location of cortical stimulation-evoked phosphenes, even after years of blindness. By accounting for eye positions, we can mimic retinal mapping as in natural sight.
Authors: Breanne Christie; Roksana Sadeghi; Arathy Kartha; Avi Caspi; Francesco V Tenore; Roberta L Klatzky; Gislin Dagnelie; Seth Billings Journal: J Neural Eng Date: 2022-06-09 Impact factor: 5.043