Eye movements and the perceived location of phosphenes generated by intracranial primary visual cortex stimulation in the blind

• Published in: Brain stimulation Vol. 14; no. 4; pp. 851 - 860
• Main Authors: Caspi, Avi, Barry, Michael P., Patel, Uday K., Salas, Michelle Armenta, Dorn, Jessy D., Roy, Arup, Niketeghad, Soroush, Greenberg, Robert J., Pouratian, Nader
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.2021; Elsevier
• Subjects: Blind; Blindness - therapy; Electric Stimulation; Eye Movements; Humans; Neurostimulation; Phosphenes; Visual Cortex; Visual Perception; Visual Prosthesis; Neurostimulation; Blind; Visual cortex; Eye movements; Visual prosthesis
• ISSN: 1935-861X; 1876-4754
• DOI: 10.1016/j.brs.2021.04.019

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. 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. 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. 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. 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. [Display omitted] •Perceived locations of phosphenes generated by visual cortical prostheses were examined.•Phosphenes maps were transformed between spatiotopic and retinotopic coordinates.•Eye movements dominate the perceived location of cortical evoked phosphenes in blind subjects.•By accounting for eye positions we can mimic retinal mapping of the visual percept from cortical electrodes.