title: Cortical responses following simultaneous and sequential retinal neurostimulation with different return configurations.
abstract: Researchers continue to develop visual prostheses towards safer and more efficacious systems. However limitations still exist in the number of stimulating channels that can be integrated. Therefore there is a need for spatial and time multiplexing techniques to provide improved performance of the current technology. In particular, bright and high-contrast visual scenes may require simultaneous activation of several electrodes. In this research, a 24-electrode array was suprachoroidally implanted in three normally-sighted cats. Multi-unit activity was recorded from the primary visual cortex. Four stimulation strategies were contrasted to provide activation of seven electrodes arranged hexagonally: simultaneous monopolar, sequential monopolar, sequential bipolar and hexapolar. Both monopolar configurations showed similar cortical activation maps. Hexapolar and sequential bipolar configurations activated a lower number of cortical channels. Overall, the return configuration played a more relevant role in cortical activation than time multiplexing and thus, rapid sequential stimulation may assist in reducing the number of channels required to activate large retinal areas.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Barriga-Rivera
authors.forename: John W
authors.initials: JW
authors.lastname: Morley
authors.forename: Nigel H
authors.initials: NH
authors.lastname: Lovell
authors.forename: Gregg J
authors.initials: GJ
authors.lastname: Suaning
mesh_terms: D000818:Animals; D002415:Cats; D004558:Electric Stimulation; D012160:Retina / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*; D057488:Visual Prosthesis