title: High-amplitude electrical stimulation can reduce elicited neuronal activity in visual prosthesis.
abstract: Retinal electrostimulation is promising a successful therapy to restore functional vision. However, a narrow stimulating current range exists between retinal neuron excitation and inhibition which may lead to misperformance of visual prostheses. As the conveyance of representation of complex visual scenes may require neighbouring electrodes to be activated simultaneously, electric field summation may contribute to reach this inhibitory threshold. This study used three approaches to assess the implications of relatively high stimulating conditions in visual prostheses: (1) in vivo, using a suprachoroidal prosthesis implanted in a feline model, (2) in vitro through electrostimulation of murine retinal preparations, and (3) in silico by computing the response of a population of retinal ganglion cells. Inhibitory stimulating conditions led to diminished cortical activity in the cat. Stimulus-response relationships showed non-monotonic profiles to increasing stimulating current. This was observed in vitro and in silico as the combined response of groups of neurons (close to the stimulating electrode) being inhibited at certain stimulating amplitudes, whilst other groups (far from the stimulating electrode) being recruited. These findings may explain the halo-like phosphene shapes reported in clinical trials and suggest that simultaneous stimulation in retinal prostheses is limited by the inhibitory threshold of the retinal ganglion cells.
authors.affiliation: Graduate School of Biomedical Engineering, UNSW, Sydney, 2052, Australia.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Barriga-Rivera
authors.affiliation: Graduate School of Biomedical Engineering, UNSW, Sydney, 2052, Australia.
authors.forename: Tianruo
authors.initials: T
authors.lastname: Guo
authors.affiliation: Graduate School of Biomedical Engineering, UNSW, Sydney, 2052, Australia.
authors.forename: Chih-Yu
authors.initials: CY
authors.lastname: Yang
authors.affiliation: Graduate School of Biomedical Engineering, UNSW, Sydney, 2052, Australia.
authors.forename: Amr Al
authors.initials: AA
authors.lastname: Abed
authors.affiliation: Graduate School of Biomedical Engineering, UNSW, Sydney, 2052, Australia.
authors.forename: Socrates
authors.initials: S
authors.lastname: Dokos
authors.affiliation: Graduate School of Biomedical Engineering, UNSW, Sydney, 2052, Australia.
authors.forename: Nigel H
authors.initials: NH
authors.lastname: Lovell
authors.affiliation: School of Medicine, Western Sydney University, Sydney, 2753, Australia.|School of Medical Science, UNSW, Sydney, 2052, Australia.
authors.forename: John W
authors.initials: JW
authors.lastname: Morley
authors.affiliation: Graduate School of Biomedical Engineering, UNSW, Sydney, 2052, Australia.|Sydney Medical School, University of Sydney, 2000, Australia.
authors.forename: Gregg J
authors.initials: GJ
authors.lastname: Suaning
mesh_terms: D000818:Animals; D002415:Cats; D004558:Electric Stimulation / Q000379:methods*; D004599:Electric Stimulation Therapy; D004567:Electrodes, Implanted; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D019919:Prosthesis Implantation / Q000379:methods; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000502:physiology*; D013238:Stereotaxic Techniques; D014785:Vision, Ocular / Q000502:physiology; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*; D057488:Visual Prosthesis