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Zaidi M, Aggarwal G, Shah NP, Karniol-Tambour O, Goetz G, Madugula SS, Gogliettino AR, Wu EG, Kling A, Brackbill N, Sher A, Litke AM, Chichilnisky EJ. Inferring light responses of primate retinal ganglion cells using intrinsic electrical signatures. J Neural Eng 2023; 20:10.1088/1741-2552/ace657. [PMID: 37433293 PMCID: PMC11067857 DOI: 10.1088/1741-2552/ace657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 07/11/2023] [Indexed: 07/13/2023]
Abstract
Objective. Retinal implants are designed to stimulate retinal ganglion cells (RGCs) in a way that restores sight to individuals blinded by photoreceptor degeneration. Reproducing high-acuity vision with these devices will likely require inferring the natural light responses of diverse RGC types in the implanted retina, without being able to measure them directly. Here we demonstrate an inference approach that exploits intrinsic electrophysiological features of primate RGCs.Approach.First, ON-parasol and OFF-parasol RGC types were identified using their intrinsic electrical features in large-scale multi-electrode recordings from macaque retina. Then, the electrically inferred somatic location, inferred cell type, and average linear-nonlinear-Poisson model parameters of each cell type were used to infer a light response model for each cell. The accuracy of the cell type classification and of reproducing measured light responses with the model were evaluated.Main results.A cell-type classifier trained on 246 large-scale multi-electrode recordings from 148 retinas achieved 95% mean accuracy on 29 test retinas. In five retinas tested, the inferred models achieved an average correlation with measured firing rates of 0.49 for white noise visual stimuli and 0.50 for natural scenes stimuli, compared to 0.65 and 0.58 respectively for models fitted to recorded light responses (an upper bound). Linear decoding of natural images from predicted RGC activity in one retina showed a mean correlation of 0.55 between decoded and true images, compared to an upper bound of 0.81 using models fitted to light response data.Significance.These results suggest that inference of RGC light response properties from intrinsic features of their electrical activity may be a useful approach for high-fidelity sight restoration. The overall strategy of first inferring cell type from electrical features and then exploiting cell type to help infer natural cell function may also prove broadly useful to neural interfaces.
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Affiliation(s)
- Moosa Zaidi
- Stanford University School of Medicine, Stanford University, Stanford, CA, United States of America
- Neurosurgery, Stanford University, Stanford, CA, United States of America
| | - Gorish Aggarwal
- Neurosurgery, Stanford University, Stanford, CA, United States of America
- Electrical Engineering, Stanford University, Stanford, CA, United States of America
| | - Nishal P Shah
- Neurosurgery, Stanford University, Stanford, CA, United States of America
| | - Orren Karniol-Tambour
- Princeton Neuroscience Institute, Princeton University, Princeton, NJ, United States of America
| | - Georges Goetz
- Neurosurgery, Stanford University, Stanford, CA, United States of America
| | - Sasidhar S Madugula
- Stanford University School of Medicine, Stanford University, Stanford, CA, United States of America
- Neurosciences, Stanford University, Stanford, CA, United States of America
| | - Alex R Gogliettino
- Neurosciences, Stanford University, Stanford, CA, United States of America
| | - Eric G Wu
- Electrical Engineering, Stanford University, Stanford, CA, United States of America
| | - Alexandra Kling
- Neurosurgery, Stanford University, Stanford, CA, United States of America
| | - Nora Brackbill
- Physics, Stanford University, Stanford, CA, United States of America
| | - Alexander Sher
- Santa Cruz Institute for Particle Physics, University of California Santa Cruz, Santa Cruz, CA, United States of America
| | - Alan M Litke
- Santa Cruz Institute for Particle Physics, University of California Santa Cruz, Santa Cruz, CA, United States of America
| | - E J Chichilnisky
- Neurosurgery, Stanford University, Stanford, CA, United States of America
- Ophthalmology, Stanford University, Stanford, CA, United States of America
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2
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Palanker D. Electronic Retinal Prostheses. Cold Spring Harb Perspect Med 2023; 13:a041525. [PMID: 36781222 PMCID: PMC10411866 DOI: 10.1101/cshperspect.a041525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Retinal prostheses are a promising means for restoring sight to patients blinded by photoreceptor atrophy. They introduce visual information by electrical stimulation of the surviving inner retinal neurons. Subretinal implants target the graded-response secondary neurons, primarily the bipolar cells, which then transfer the information to the ganglion cells via the retinal neural network. Therefore, many features of natural retinal signal processing can be preserved in this approach if the inner retinal network is retained. Epiretinal implants stimulate primarily the ganglion cells, and hence should encode the visual information in spiking patterns, which, ideally, should match the target cell types. Currently, subretinal arrays are being developed primarily for restoration of central vision in patients impaired by age-related macular degeneration (AMD), while epiretinal implants-for patients blinded by retinitis pigmentosa, where the inner retina is less preserved. This review describes the concepts and technologies, preclinical characterization of prosthetic vision and clinical outcomes, and provides a glimpse into future developments.
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Affiliation(s)
- Daniel Palanker
- Department of Ophthalmology and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305, USA
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3
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Gogliettino AR, Madugula SS, Grosberg LE, Vilkhu RS, Brown J, Nguyen H, Kling A, Hottowy P, Dąbrowski W, Sher A, Litke AM, Chichilnisky EJ. High-Fidelity Reproduction of Visual Signals by Electrical Stimulation in the Central Primate Retina. J Neurosci 2023; 43:4625-4641. [PMID: 37188516 PMCID: PMC10286946 DOI: 10.1523/jneurosci.1091-22.2023] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 05/08/2023] [Accepted: 05/10/2023] [Indexed: 05/17/2023] Open
Abstract
Electrical stimulation of retinal ganglion cells (RGCs) with electronic implants provides rudimentary artificial vision to people blinded by retinal degeneration. However, current devices stimulate indiscriminately and therefore cannot reproduce the intricate neural code of the retina. Recent work has demonstrated more precise activation of RGCs using focal electrical stimulation with multielectrode arrays in the peripheral macaque retina, but it is unclear how effective this can be in the central retina, which is required for high-resolution vision. This work probes the neural code and effectiveness of focal epiretinal stimulation in the central macaque retina, using large-scale electrical recording and stimulation ex vivo The functional organization, light response properties, and electrical properties of the major RGC types in the central retina were mostly similar to the peripheral retina, with some notable differences in density, kinetics, linearity, spiking statistics, and correlations. The major RGC types could be distinguished by their intrinsic electrical properties. Electrical stimulation targeting parasol cells revealed similar activation thresholds and reduced axon bundle activation in the central retina, but lower stimulation selectivity. Quantitative evaluation of the potential for image reconstruction from electrically evoked parasol cell signals revealed higher overall expected image quality in the central retina. An exploration of inadvertent midget cell activation suggested that it could contribute high spatial frequency noise to the visual signal carried by parasol cells. These results support the possibility of reproducing high-acuity visual signals in the central retina with an epiretinal implant.SIGNIFICANCE STATEMENT Artificial restoration of vision with retinal implants is a major treatment for blindness. However, present-day implants do not provide high-resolution visual perception, in part because they do not reproduce the natural neural code of the retina. Here, we demonstrate the level of visual signal reproduction that is possible with a future implant by examining how accurately responses to electrical stimulation of parasol retinal ganglion cells can convey visual signals. Although the precision of electrical stimulation in the central retina was diminished relative to the peripheral retina, the quality of expected visual signal reconstruction in parasol cells was greater. These findings suggest that visual signals could be restored with high fidelity in the central retina using a future retinal implant.
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Affiliation(s)
- Alex R Gogliettino
- Neurosciences PhD Program, Stanford University, Stanford, California 94305
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305
| | - Sasidhar S Madugula
- Neurosciences PhD Program, Stanford University, Stanford, California 94305
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305
- Stanford School of Medicine, Stanford University, Stanford, California 94305
| | - Lauren E Grosberg
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305
- Department of Neurosurgery, Stanford University, Stanford, California 94305
| | - Ramandeep S Vilkhu
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305
- Department of Electrical Engineering, Stanford University, Stanford, California 94305
| | - Jeff Brown
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305
- Department of Neurosurgery, Stanford University, Stanford, California 94305
- Department of Electrical Engineering, Stanford University, Stanford, California 94305
| | - Huy Nguyen
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305
| | - Alexandra Kling
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305
- Department of Neurosurgery, Stanford University, Stanford, California 94305
| | - Paweł Hottowy
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, 30-059, Kraków, Poland
| | - Władysław Dąbrowski
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, 30-059, Kraków, Poland
| | - Alexander Sher
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, Santa Cruz, California 95064
| | - Alan M Litke
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, Santa Cruz, California 95064
| | - E J Chichilnisky
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305
- Department of Neurosurgery, Stanford University, Stanford, California 94305
- Department of Electrical Engineering, Stanford University, Stanford, California 94305
- Department of Ophthalmology, Stanford University, Stanford, California 94305
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4
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Jain V, Forssell M, Tansel DZ, Goswami C, Fedder GK, Grover P, Chamanzar M. Focused Epicranial Brain Stimulation by Spatial Sculpting of Pulsed Electric Fields Using High Density Electrode Arrays. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023:e2207251. [PMID: 37114777 PMCID: PMC10369286 DOI: 10.1002/advs.202207251] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 03/10/2023] [Indexed: 06/19/2023]
Abstract
Transcranial electrical neuromodulation of the central nervous system is used as a non-invasive method to induce neural and behavioral responses, yet targeted non-invasive electrical stimulation of the brain with high spatial resolution remains elusive. This work demonstrates a focused, steerable, high-density epicranial current stimulation (HD-ECS) approach to evoke neural activity. Custom-designed high-density (HD) flexible surface electrode arrays are employed to apply high-resolution pulsed electric currents through skull to achieve localized stimulation of the intact mouse brain. The stimulation pattern is steered in real time without physical movement of the electrodes. Steerability and focality are validated at the behavioral, physiological, and cellular levels using motor evoked potentials (MEPs), intracortical recording, and c-fos immunostaining. Whisker movement is also demonstrated to further corroborate the selectivity and steerability. Safety characterization confirmed no significant tissue damage following repetitive stimulation. This method can be used to design novel therapeutics and implement next-generation brain interfaces.
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Affiliation(s)
- Vishal Jain
- Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA-15213, USA
| | - Mats Forssell
- Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA-15213, USA
| | - Derya Z Tansel
- Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA-15213, USA
| | - Chaitanya Goswami
- Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA-15213, USA
| | - Gary K Fedder
- Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA-15213, USA
| | - Pulkit Grover
- Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA-15213, USA
- Neuroscience Insttitute, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Maysamreza Chamanzar
- Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA-15213, USA
- Neuroscience Insttitute, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
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5
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Madugula SS, Gogliettino AR, Zaidi M, Aggarwal G, Kling A, Shah NP, Brown JB, Vilkhu R, Hays MR, Nguyen H, Fan V, Wu EG, Hottowy P, Sher A, Litke AM, Silva RA, Chichilnisky EJ. Focal electrical stimulation of human retinal ganglion cells for vision restoration. J Neural Eng 2022; 19:066040. [PMID: 36533865 PMCID: PMC10010036 DOI: 10.1088/1741-2552/aca5b5] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 11/24/2022] [Indexed: 11/25/2022]
Abstract
Objective. Vision restoration with retinal implants is limited by indiscriminate simultaneous activation of many cells and cell types, which is incompatible with reproducing the neural code of the retina. Recent work has shown that primate retinal ganglion cells (RGCs), which transmit visual information to the brain, can be directly electrically activated with single-cell, single-spike, cell-type precision - however, this possibility has never been tested in the human retina. In this study we aim to characterize, for the first time, direct in situ extracellular electrical stimulation of individual human RGCs.Approach. Extracellular electrical stimulation of individual human RGCs was conducted in three human retinas ex vivo using a custom large-scale, multi-electrode array capable of simultaneous recording and stimulation. Measured activation properties were compared directly to extensive results from macaque.Main results. Precise activation was in many cases possible without activating overlying axon bundles, at low stimulation current levels similar to those used in macaque. The major RGC types could be identified and targeted based on their distinctive electrical signatures. The measured electrical activation properties of RGCs, combined with a dynamic stimulation algorithm, was sufficient to produce an evoked visual signal that was nearly optimal given the constraints of the interface.Significance. These results suggest the possibility of high-fidelity vision restoration in humans using bi-directional epiretinal implants.
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Affiliation(s)
- Sasidhar S Madugula
- Neurosciences PhD Program, Stanford University, Stanford, CA, United States of America
- School of Medicine, Stanford University, Stanford, CA, United States of America
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
| | - Alex R Gogliettino
- Neurosciences PhD Program, Stanford University, Stanford, CA, United States of America
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
| | - Moosa Zaidi
- Department of Neurosurgery, Stanford University, Stanford, CA, United States of America
- School of Medicine, Stanford University, Stanford, CA, United States of America
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
| | - Gorish Aggarwal
- Department of Neurosurgery, Stanford University, Stanford, CA, United States of America
- Department of Electrical Engineering, Stanford University, Stanford, CA, United States of America
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
| | - Alexandra Kling
- Department of Neurosurgery, Stanford University, Stanford, CA, United States of America
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
| | - Nishal P Shah
- Department of Neurosurgery, Stanford University, Stanford, CA, United States of America
- Department of Electrical Engineering, Stanford University, Stanford, CA, United States of America
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
| | - Jeff B Brown
- Department of Electrical Engineering, Stanford University, Stanford, CA, United States of America
| | - Ramandeep Vilkhu
- Department of Electrical Engineering, Stanford University, Stanford, CA, United States of America
| | - Madeline R Hays
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
- Department of Bioengineering, Stanford University, Stanford, CA, United States of America
| | - Huy Nguyen
- Department of Neurosurgery, Stanford University, Stanford, CA, United States of America
| | - Victoria Fan
- Department of Neurosurgery, Stanford University, Stanford, CA, United States of America
| | - Eric G Wu
- Department of Electrical Engineering, Stanford University, Stanford, CA, United States of America
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
| | - Pawel Hottowy
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Krakow, Poland
| | - Alexander Sher
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, CA, United States of America
| | - Alan M Litke
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, CA, United States of America
| | - Ruwan A Silva
- Department of Ophthalmology, Stanford University, Stanford, CA, United States of America
| | - E J Chichilnisky
- Department of Neurosurgery, Stanford University, Stanford, CA, United States of America
- Department of Ophthalmology, Stanford University, Stanford, CA, United States of America
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
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6
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Wang BY, Chen ZC, Bhuckory M, Huang T, Shin A, Zuckerman V, Ho E, Rosenfeld E, Galambos L, Kamins T, Mathieson K, Palanker D. Electronic photoreceptors enable prosthetic visual acuity matching the natural resolution in rats. Nat Commun 2022; 13:6627. [PMID: 36333326 PMCID: PMC9636145 DOI: 10.1038/s41467-022-34353-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 10/24/2022] [Indexed: 11/06/2022] Open
Abstract
Localized stimulation of the inner retinal neurons for high-acuity prosthetic vision requires small pixels and minimal crosstalk from the neighboring electrodes. Local return electrodes within each pixel limit the crosstalk, but they over-constrain the electric field, thus precluding the efficient stimulation with subretinal pixels smaller than 55 μm. Here we demonstrate a high-resolution prosthetic vision based on a novel design of a photovoltaic array, where field confinement is achieved dynamically, leveraging the adjustable conductivity of the diodes under forward bias to turn the designated pixels into transient returns. We validated the computational modeling of the field confinement in such an optically-controlled circuit by in-vitro and in-vivo measurements. Most importantly, using this strategy, we demonstrated that the grating acuity with 40 μm pixels matches the pixel pitch, while with 20 μm pixels, it reaches the 28 μm limit of the natural visual resolution in rats. This method enables customized field shaping based on individual retinal thickness and distance from the implant, paving the way to higher acuity of prosthetic vision in atrophic macular degeneration.
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Affiliation(s)
- Bing-Yi Wang
- Department of Physics, Stanford University, Stanford, CA, USA.
| | - Zhijie Charles Chen
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA.
| | - Mohajeet Bhuckory
- grid.168010.e0000000419368956Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA USA ,grid.168010.e0000000419368956Department of Ophthalmology, Stanford University, Stanford, CA USA
| | - Tiffany Huang
- grid.168010.e0000000419368956Department of Electrical Engineering, Stanford University, Stanford, CA USA
| | - Andrew Shin
- grid.168010.e0000000419368956Department of Material Science, Stanford University, Stanford, CA USA
| | - Valentina Zuckerman
- grid.168010.e0000000419368956Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA USA
| | - Elton Ho
- grid.168010.e0000000419368956Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA USA ,grid.168010.e0000000419368956Department of Ophthalmology, Stanford University, Stanford, CA USA
| | - Ethan Rosenfeld
- grid.168010.e0000000419368956Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA USA
| | - Ludwig Galambos
- grid.168010.e0000000419368956Department of Electrical Engineering, Stanford University, Stanford, CA USA
| | - Theodore Kamins
- grid.168010.e0000000419368956Department of Electrical Engineering, Stanford University, Stanford, CA USA ,grid.168010.e0000000419368956Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA USA
| | - Keith Mathieson
- grid.11984.350000000121138138Department of Physics, Institute of Photonics, University of Strathclyde, Glasgow, Scotland UK
| | - Daniel Palanker
- grid.168010.e0000000419368956Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA USA ,grid.168010.e0000000419368956Department of Ophthalmology, Stanford University, Stanford, CA USA
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7
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Caravaca-Rodriguez D, Gaytan SP, Suaning GJ, Barriga-Rivera A. Implications of Neural Plasticity in Retinal Prosthesis. Invest Ophthalmol Vis Sci 2022; 63:11. [PMID: 36251317 DOI: 10.1167/iovs.63.11.11] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Retinal degenerative diseases such as retinitis pigmentosa cause a progressive loss of photoreceptors that eventually prevents the affected person from perceiving visual sensations. The absence of a visual input produces a neural rewiring cascade that propagates along the visual system. This remodeling occurs first within the retina. Then, subsequent neuroplastic changes take place at higher visual centers in the brain, produced by either the abnormal neural encoding of the visual inputs delivered by the diseased retina or as the result of an adaptation to visual deprivation. While retinal implants can activate the surviving retinal neurons by delivering electric current, the unselective activation patterns of the different neural populations that exist in the retinal layers differ substantially from those in physiologic vision. Therefore, artificially induced neural patterns are being delivered to a brain that has already undergone important neural reconnections. Whether or not the modulation of this neural rewiring can improve the performance for retinal prostheses remains a critical question whose answer may be the enabler of improved functional artificial vision and more personalized neurorehabilitation strategies.
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Affiliation(s)
- Daniel Caravaca-Rodriguez
- Department of Applied Physics III, Technical School of Engineering, Universidad de Sevilla, Sevilla, Spain
| | - Susana P Gaytan
- Department of Physiology, Universidad de Sevilla, Sevilla, Spain
| | - Gregg J Suaning
- School of Biomedical Engineering, University of Sydney, Sydney, Australia
| | - Alejandro Barriga-Rivera
- Department of Applied Physics III, Technical School of Engineering, Universidad de Sevilla, Sevilla, Spain.,School of Biomedical Engineering, University of Sydney, Sydney, Australia
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8
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Haq W, Basavaraju S, Speck A, Zrenner E. Nature-inspired saccadic-like electrical stimulation paradigm promotes sustained retinal ganglion cell responses by spatiotemporally alternating activation of contiguous multi-electrode patterns. J Neural Eng 2022; 19. [PMID: 36066085 DOI: 10.1088/1741-2552/ac8ad0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 08/18/2022] [Indexed: 11/12/2022]
Abstract
Objective. Retinal electrical stimulation using multi-electrode arrays (MEAs) aims to restore visual object perception in blind patients. However, the rate and duration of the artificial visual sensations are limited due to the rapid response decay of the stimulated neurons. Hence, we investigated a novel nature-inspired saccadic-like stimulation paradigm (biomimetic) to evoke sustained retinal responses. For implementation, the macroelectrode was replaced by several contiguous microelectrodes and activated non-simultaneously but alternating topologically.Approach.MEAs with hexagonally arranged electrodes were utilized to simulate and record mouse retinal ganglion cells (RGCs). Two shapes were presented electrically using MEAs: a 6e-hexagon (six hexagonally arranged 10µm electrodes; 6e-hexagon diameter: 80µm) and a double-bar (180µm spaced, 320µm in length). Electrodes of each shape were activated in three different modes (simultaneous, circular, and biomimetic ('zig-zag')), stimulating at different frequencies (1-20 Hz).Main results.The biomimetic stimulation generated enhanced RGC responses increasing the activity rate by 87.78%. In the spatiotemporal context, the electrical representation of the 6e-hexagon produced sustained and local RGC responses (∼130µm corresponding to ∼2.5° of the human visual angle) for up to 90 s at 10 Hz stimulation and resolved the electrically presented double-bar. In contrast, during conventional simultaneous stimulation, the responses were poor and declined within seconds. Similarly, the applicability of the biomimetic mode for retinal implants (7 × 8 pixels) was successfully demonstrated. An object shape impersonating a smile was presented electrically, and the recorded data were used to emulate the implant's performance. The spatiotemporal pixel mapping of the activity produced a complete retinal image of the smile.Significance.The application of electrical stimulation in the biomimetic mode produced locally enhanced RGC responses with significantly reduced fading effects and yielded advanced spatiotemporal performance reflecting the presented electrode shapes in the mapped activity imprint. Therefore, it is likely that the RGC responses persist long enough to evoke visual perception and generate a seamless image, taking advantage of the flicker fusion. Hence, replacing the implant's macroelectrodes with microelectrodes and their activation in a topologically alternating biomimetic fashion may overcome the patient's perceptual image fading, thereby enhancing the spatiotemporal characteristics of artificial vision.
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Affiliation(s)
- Wadood Haq
- Neuroretinal Electrophysiology and Imaging, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Elfriede-Aulhorn-Str. 5-7, D-72076 Tübingen, Germany
| | - Sunetra Basavaraju
- Neuroretinal Electrophysiology and Imaging, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Elfriede-Aulhorn-Str. 5-7, D-72076 Tübingen, Germany
| | - Achim Speck
- Neuroretinal Electrophysiology and Imaging, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Elfriede-Aulhorn-Str. 5-7, D-72076 Tübingen, Germany
| | - Eberhart Zrenner
- Neuroretinal Electrophysiology and Imaging, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Elfriede-Aulhorn-Str. 5-7, D-72076 Tübingen, Germany
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9
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Roh H, Otgondemberel Y, Im M. Short pulses of epiretinal prostheses evoke network-mediated responses in retinal ganglion cells by stimulating presynaptic neurons. J Neural Eng 2022; 19. [PMID: 36055185 DOI: 10.1088/1741-2552/ac8ed7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 09/02/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Microelectronic retinal implant aims to restore functional vision with electric stimulation. Short pulses are generally known to directly activate retinal ganglion cells (RGCs) with a notion of one or two spike(s) per pulse. In the present work, we systematically explore network-mediated responses that arise from various short pulses in both normal and degenerate retinas. APPROACH Cell-attached patch clamping was used to record spiking responses of RGCs in wild-type (C57BL/6J) and retinal degeneration (rd10) mice. Alpha RGCs of the mouse retinas were targeted by their large soma sizes and classified by their responses to spot flashes. Then, RGCs were electrically stimulated by various conditions such as duration (100-460 μs), count (1-10), amplitude (100-400 μA), and repeating frequency (10-40 Hz) of short pulses. Also, their responses were compared with each own response to a single 4-ms-long pulse which is known to evoke strong indirect responses. MAIN RESULTS Short pulses evoked strong network-mediated responses not only in both ON and OFF types of RGCs in the healthy retinas but also in RGCs of the severely degenerate retina. However, the spike timing consistency across repeats not decreased significantly in the rd10 RGCs compared to the healthy ON and OFF RGCs. Network-mediated responses of ON RGCs were highly dependent on the current amplitude of stimuli but much less on the pulse count and the repetition frequency. In contrast, responses of OFF RGCs were more influenced by the number of stimuli than the current amplitude. SIGNIFICANCE Our results demonstrate that short pulses also elicit indirect responses by activating presynaptic neurons. In the case of the commercial retinal prostheses using repeating short pulses, there is a possibility that the performance of clinical devices is highly related to the preserved retinal circuits. Therefore, examination of surviving retinal neurons in patients would be necessary to improve the efficacy of retinal prostheses.
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Affiliation(s)
- Hyeonhee Roh
- Korea Institute of Science and Technology (KIST), 5 Hwarang-ro 14-gil, Seongbuk-gu, Seoul, 02792, Korea (the Republic of)
| | - Yanjinsuren Otgondemberel
- Brain Science Institute, Korea Institute of Science and Technology (KIST), 5 Hwarang-ro 14-gil, Seongbuk-gu, Seoul, 02792, Korea (the Republic of)
| | - Maesoon Im
- Brain Science Institute, Center for BioMicrosystems, Korea Institute of Science and Technology, 5 Hwarang-ro 14-gil, Seongbuk-gu, L7325B, Seoul, Seoul, Seoul, 02792, Korea (the Republic of)
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10
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Italiano ML, Guo T, Lovell NH, Tsai D. Improving the spatial resolution of artificial vision using midget retinal ganglion cell populations modelled at the human fovea. J Neural Eng 2022; 19. [PMID: 35609556 DOI: 10.1088/1741-2552/ac72c2] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 05/24/2022] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Retinal prostheses seek to create artificial vision by stimulating surviving retinal neurons of patients with profound vision impairment. Notwithstanding tremendous research efforts, the performance of all implants tested to date has remained rudimentary, incapable of overcoming the threshold for legal blindness. To maximize the perceptual efficacy of retinal prostheses, a device must be capable of controlling retinal neurons with greater spatiotemporal precision. Most studies of retinal stimulation were derived from either non-primate species or the peripheral primate retina. We investigated if artificial stimulation could leverage the high spatial resolution afforded by the neural substrates at the primate fovea and surrounding regions to achieve improved percept qualities. APPROACH We began by developing a new computational model capable of generating anatomically accurate retinal ganglion cell (RGC) populations within the human central retina. Next, multiple RGC populations across the central retina were stimulated in-silico to compare clinical and recently proposed neurostimulation configurations based on their ability to improve perceptual efficacy and reduce activation thresholds. MAIN RESULTS Our model uniquely upholds eccentricity-dependent characteristics such as RGC density and dendritic field diameter, whilst incorporating anatomically accurate features such as axon projection and three-dimensional RGC layering, features often forgone in favor of reduced computational complexity. Following epiretinal stimulation, the RGCs in our model produced response patterns in shapes akin to the complex percepts reported in clinical trials. Our results also demonstrated that even within the neuron-dense central retina, epiretinal stimulation using a multi-return hexapolar electrode arrangement could reliably achieve spatially focused RGC activation and could achieve single-cell excitation in 74% of all tested locations. SIGNIFICANCE This study establishes an anatomically accurate three-dimensional model of the human central retina and demonstrates the potential for an epiretinal hexapolar configuration to achieve consistent, spatially confined retinal responses, even within the neuron-dense foveal region. Our results promote the prospect and optimization of higher spatial resolution in future epiretinal implants.
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Affiliation(s)
- Michael Lewis Italiano
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Sydney, New South Wales, 2052, AUSTRALIA
| | - Tianruo Guo
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Sydney, New South Wales, 2052, AUSTRALIA
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Sydney, New South Wales, 2052, AUSTRALIA
| | - David Tsai
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Sydney, New South Wales, 2052, AUSTRALIA
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11
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Raghuram V, Werginz P, Fried SI, Timko BP. Morphological Factors that Underlie Neural Sensitivity to Stimulation in the Retina. ADVANCED NANOBIOMED RESEARCH 2022; 1. [PMID: 35399546 DOI: 10.1002/anbr.202100069] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Retinal prostheses are a promising therapeutic intervention for patients afflicted by outer retinal degenerative diseases like retinitis pigmentosa and age-related macular degeneration. While significant advances in the development of retinal implants have been made, the quality of vision elicited by these devices remains largely sub-optimal. The variability in the responses produced by retinal devices is most likely due to the differences between the natural cell type-specific signaling that occur in the healthy retina vs. the non-specific activation of multiple cell types arising from artificial stimulation. In order to replicate these natural signaling patterns, stimulation strategies must be capable of preferentially activating specific RGC types. To design more selective stimulation strategies, a better understanding of the morphological factors that underlie the sensitivity to prosthetic stimulation must be developed. This review will focus on the role that different anatomical components play in driving the direct activation of RGCs by extracellular stimulation. Briefly, it will (1) characterize the variability in morphological properties of α-RGCs, (2) detail the influence of morphology on the direct activation of RGCs by electric stimulation, and (3) describe some of the potential biophysical mechanisms that could explain differences in activation thresholds and electrically evoked responses between RGC types.
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Affiliation(s)
- Vineeth Raghuram
- Boston VA Healthcare System, 150 S Huntington Ave, Boston, MA 02130, USA.,Dept. of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, USA.,Dept. of Neurosurgery, Massachusetts General Hospital - Harvard Medical School, 50 Blossom Street, Boston, MA, 02114
| | - Paul Werginz
- Institute for Analysis and Scientific Computing, Vienna University of Technology, Wiedner Hauptstrasse 8-10, Vienna, Austria.,Dept. of Neurosurgery, Massachusetts General Hospital - Harvard Medical School, 50 Blossom Street, Boston, MA, 02114
| | - Shelley I Fried
- Boston VA Healthcare System, 150 S Huntington Ave, Boston, MA 02130, USA.,Dept. of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, USA.,Dept. of Neurosurgery, Massachusetts General Hospital - Harvard Medical School, 50 Blossom Street, Boston, MA, 02114
| | - Brian P Timko
- Dept. of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, USA
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12
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Vilkhu RS, Madugula SS, Grosberg LE, Gogliettino AR, Hottowy P, Dabrowski W, Sher A, Litke AM, Mitra S, Chichilnisky EJ. Spatially patterned bi-electrode epiretinal stimulation for axon avoidance at cellular resolution. J Neural Eng 2021; 18. [PMID: 34710857 DOI: 10.1088/1741-2552/ac3450] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 10/28/2021] [Indexed: 11/12/2022]
Abstract
Objective.Epiretinal prostheses are designed to restore vision to people blinded by photoreceptor degenerative diseases by stimulating surviving retinal ganglion cells (RGCs), which carry visual signals to the brain. However, inadvertent stimulation of RGCs at their axons can result in non-focal visual percepts, limiting the quality of artificial vision. Theoretical work has suggested that axon activation can be avoided with current stimulation designed to minimize the second spatial derivative of the induced extracellular voltage along the axon. However, this approach has not been verified experimentally at the resolution of single cells.Approach.In this work, a custom multi-electrode array (512 electrodes, 10μm diameter, 60μm pitch) was used to stimulate and record RGCs in macaque retinaex vivoat single-cell, single-spike resolution. RGC activation thresholds resulting from bi-electrode stimulation, which consisted of bipolar currents simultaneously delivered through two electrodes straddling an axon, were compared to activation thresholds from traditional single-electrode stimulation.Main results.On average, across three retinal preparations, the bi-electrode stimulation strategy reduced somatic activation thresholds (∼21%) while increasing axonal activation thresholds (∼14%), thus favoring selective somatic activation. Furthermore, individual examples revealed rescued selective activation of somas that was not possible with any individual electrode.Significance.This work suggests that a bi-electrode epiretinal stimulation strategy can reduce inadvertent axonal activation at cellular resolution, for high-fidelity artificial vision.
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Affiliation(s)
- Ramandeep S Vilkhu
- Department of Electrical Engineering, Stanford University, Stanford, CA, United States of America
| | - Sasidhar S Madugula
- Departments of Neurosurgery, Ophthalmology, and Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
| | - Lauren E Grosberg
- Departments of Neurosurgery, Ophthalmology, and Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
| | - Alex R Gogliettino
- Departments of Neurosurgery, Ophthalmology, and Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
| | - Pawel Hottowy
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Krakow 30-059, Poland
| | - Wladyslaw Dabrowski
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Krakow 30-059, Poland
| | - Alexander Sher
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, CA, United States of America
| | - Alan M Litke
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, CA, United States of America
| | - Subhasish Mitra
- Department of Electrical Engineering, Stanford University, Stanford, CA, United States of America
| | - E J Chichilnisky
- Departments of Neurosurgery, Ophthalmology, and Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
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13
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Abstract
Visual images can be described in terms of the illuminants and objects that are causal to the light reaching the eye, the retinal image, its neural representation, or how the image is perceived. Respecting the differences among these distinct levels of description can be challenging but is crucial for a clear understanding of color vision. This article approaches color by reviewing what is known about its neural representation in the early visual cortex, with a brief description of signals in the eye and the thalamus for context. The review focuses on the properties of single neurons and advances the general theme that experimental approaches based on knowledge of feedforward signals have promoted greater understanding of the neural code for color than approaches based on correlating single-unit responses with color perception. New data from area V1 illustrate the strength of the feedforward approach. Future directions for progress in color neurophysiology are discussed: techniques for improved single-neuron characterization, for investigations of neural populations and small circuits, and for the analysis of natural image statistics.
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Affiliation(s)
- Gregory D Horwitz
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195, USA; .,Washington National Primate Research Center, University of Washington, Seattle, Washington 98121, USA
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14
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Corna A, Ramesh P, Jetter F, Lee MJ, Macke JH, Zeck G. Discrimination of simple objects decoded from the output of retinal ganglion cells upon sinusoidal electrical stimulation. J Neural Eng 2021; 18. [PMID: 34049288 DOI: 10.1088/1741-2552/ac0679] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 05/28/2021] [Indexed: 11/12/2022]
Abstract
Objective. Most neuroprosthetic implants employ pulsatile square-wave electrical stimuli, which are significantly different from physiological inter-neuronal communication. In case of retinal neuroprosthetics, which use a certain type of pulsatile stimuli, reliable object and contrast discrimination by implanted blind patients remained challenging. Here we investigated to what extent simple objects can be discriminated from the output of retinal ganglion cells (RGCs) upon sinusoidal stimulation.Approach. Spatially confined objects were formed by different combinations of 1024 stimulating microelectrodes. The RGC activity in theex vivoretina of photoreceptor-degenerated mouse, of healthy mouse or of primate was recorded simultaneously using an interleaved recording microelectrode array implemented in a CMOS-based chip.Main results. We report that application of sinusoidal electrical stimuli (40 Hz) in epiretinal configuration instantaneously and reliably modulates the RGC activity in spatially confined areas at low stimulation threshold charge densities (40 nC mm-2). Classification of overlapping but spatially displaced objects (1° separation) was achieved by distinct spiking activity of selected RGCs. A classifier (regularized logistic regression) discriminated spatially displaced objects (size: 5.5° or 3.5°) with high accuracy (90% or 62%). Stimulation with low artificial contrast (10%) encoded by different stimulus amplitudes generated RGC activity, which was classified with an accuracy of 80% for large objects (5.5°).Significance. We conclude that time-continuous smooth-wave stimulation provides robust, localized neuronal activation in photoreceptor-degenerated retina, which may enable future artificial vision at high temporal, spatial and contrast resolution.
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Affiliation(s)
- Andrea Corna
- Neurophysics, NMI Natural and Medical Sciences Institute at the University Tübingen, Reutlingen, Germany.,Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany.,Graduate School of Neural Information Processing/International Max Planck Research School, Tübingen, Germany.,Biomedical Electronics and Systems, EMCE Institute, TU Wien, Wien, Austria
| | - Poornima Ramesh
- Computational Neuroengineering, Technical University München, München, Germany.,Machine Learning in Science, University of Tübingen, Tübingen, Germany
| | - Florian Jetter
- Neurophysics, NMI Natural and Medical Sciences Institute at the University Tübingen, Reutlingen, Germany.,Graduate School of Neural Information Processing/International Max Planck Research School, Tübingen, Germany
| | - Meng-Jung Lee
- Neurophysics, NMI Natural and Medical Sciences Institute at the University Tübingen, Reutlingen, Germany.,Graduate School of Neural Information Processing/International Max Planck Research School, Tübingen, Germany
| | - Jakob H Macke
- Computational Neuroengineering, Technical University München, München, Germany.,Machine Learning in Science, University of Tübingen, Tübingen, Germany.,MPI for Intelligent Systems, Tübingen, Germany
| | - Günther Zeck
- Neurophysics, NMI Natural and Medical Sciences Institute at the University Tübingen, Reutlingen, Germany.,Biomedical Electronics and Systems, EMCE Institute, TU Wien, Wien, Austria
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15
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Moleirinho S, Whalen AJ, Fried SI, Pezaris JS. The impact of synchronous versus asynchronous electrical stimulation in artificial vision. J Neural Eng 2021; 18. [PMID: 33900206 DOI: 10.1088/1741-2552/abecf1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Accepted: 03/09/2021] [Indexed: 11/12/2022]
Abstract
Visual prosthesis devices designed to restore sight to the blind have been under development in the laboratory for several decades. Clinical translation continues to be challenging, due in part to gaps in our understanding of critical parameters such as how phosphenes, the electrically-generated pixels of artificial vision, can be combined to form images. In this review we explore the effects that synchronous and asynchronous electrical stimulation across multiple electrodes have in evoking phosphenes. Understanding how electrical patterns influence phosphene generation to control object binding and perception of visual form is fundamental to creation of a clinically successful prosthesis.
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Affiliation(s)
- Susana Moleirinho
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, United States of America.,Department of Neurosurgery, Harvard Medical School, Boston, MA, United States of America
| | - Andrew J Whalen
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, United States of America.,Department of Neurosurgery, Harvard Medical School, Boston, MA, United States of America
| | - Shelley I Fried
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, United States of America.,Department of Neurosurgery, Harvard Medical School, Boston, MA, United States of America.,Boston VA Healthcare System, Boston, MA, United States of America
| | - John S Pezaris
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, United States of America.,Department of Neurosurgery, Harvard Medical School, Boston, MA, United States of America
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16
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Shah NP, Chichilnisky EJ. Computational challenges and opportunities for a bi-directional artificial retina. J Neural Eng 2020; 17:055002. [PMID: 33089827 DOI: 10.1088/1741-2552/aba8b1] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
A future artificial retina that can restore high acuity vision in blind people will rely on the capability to both read (observe) and write (control) the spiking activity of neurons using an adaptive, bi-directional and high-resolution device. Although current research is focused on overcoming the technical challenges of building and implanting such a device, exploiting its capabilities to achieve more acute visual perception will also require substantial computational advances. Using high-density large-scale recording and stimulation in the primate retina with an ex vivo multi-electrode array lab prototype, we frame several of the major computational problems, and describe current progress and future opportunities in solving them. First, we identify cell types and locations from spontaneous activity in the blind retina, and then efficiently estimate their visual response properties by using a low-dimensional manifold of inter-retina variability learned from a large experimental dataset. Second, we estimate retinal responses to a large collection of relevant electrical stimuli by passing current patterns through an electrode array, spike sorting the resulting recordings and using the results to develop a model of evoked responses. Third, we reproduce the desired responses for a given visual target by temporally dithering a diverse collection of electrical stimuli within the integration time of the visual system. Together, these novel approaches may substantially enhance artificial vision in a next-generation device.
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Affiliation(s)
- Nishal P Shah
- Department of Electrical Engineering, Stanford University, Stanford, CA, United States of America. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America. Department of Neurosurgery, Stanford University, Stanford, CA, United States of America. Author to whom any correspondence should be addressed
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17
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Hou Z, Al-Atabany W, Farag R, Vuong QC, Mokhov A, Degenaar P. A scalable data transmission scheme for implantable optogenetic visual prostheses. J Neural Eng 2020; 17:055001. [DOI: 10.1088/1741-2552/abaf2e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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18
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Yoon YJ, Lee JI, Jang YJ, An S, Kim JH, Fried SI, Im M. Retinal Degeneration Reduces Consistency of Network-Mediated Responses Arising in Ganglion Cells to Electric Stimulation. IEEE Trans Neural Syst Rehabil Eng 2020; 28:1921-1930. [PMID: 32746297 PMCID: PMC7518787 DOI: 10.1109/tnsre.2020.3003345] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Retinal prostheses use periodic repetition of electrical stimuli to form artificial vision. To enhance the reliability of evoked visual percepts, repeating stimuli need to evoke consistent spiking activity in individual retinal ganglion cells (RGCs). However, it is not well known whether outer retinal degeneration alters the consistency of RGC responses. Hence, here we systematically investigated the trial-to-trial variability in network-mediated responses as a function of the degeneration level. We patch-clamp recorded spikes in ON and OFF types of alpha RGCs from r d10 mice at four different postnatal days (P15, P19, P31, and P60), representing distinct stages of degeneration. To assess the consistency of responses, we analyzed variances in spike count and timing across repeats of the same stimulus delivered multiple times. We found the trial-to-trial variability of network-mediated responses increased considerably as the disease progressed. Compared to responses taken before degeneration onset, those of degenerate retinas showed up to ~70% higher variability (Fano Factor) in spike counts (p < 0.001) and ~95% lower correlation level in spike timing (p < 0.001). These results indicate consistency weakens significantly in electrically-evoked network-mediated responses and therefore raise concerns about the ability of microelectronic retinal implants to elicit consistent visual percepts at advanced stages of retinal degeneration.
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19
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Werginz P, Raghuram V, Fried SI. The relationship between morphological properties and thresholds to extracellular electric stimulation in α RGCs. J Neural Eng 2020; 17:045015. [PMID: 32736374 DOI: 10.1088/1741-2552/abab47] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVE Retinal prostheses strive to restore vison to patients that are blind from retinal degeneration by electrically stimulating surviving retinal ganglion cells (RGCs). The quality of elicited percepts remains limited however and it is desirable to develop improved stimulation strategies. Here, we examine how the anatomical and biophysical properties of RGCs influence activation thresholds, including the effects of variations found naturally. APPROACH Detailed reconstructions were made of a large number of mouse α RGCs and were used to create an array of model cells; the models were used to study the effects of individual anatomical features on activation threshold to electric stimulation. Stimulation was delivered epiretinally from a point-source or disk electrode and consisted of monophasic or biphasic rectangular pulses. MAIN RESULTS Modeling results show that the region of minimum threshold always is within the axon initial segment (AIS). The properties of this region as well as the absolute value of the minimum threshold are dependent on the length of the AIS as well as on the relative composition of sodium channels within the AIS. Other morphological features, including cell size, dendritic field size and the distance between the AIS and the soma had only a minimal influence on thresholds. Introducing even a small number of low-threshold Nav1.6 channels into the AIS was sufficient to lower minimum thresholds substantially although further increases in Nav1.6 had diminishing effects. The distance between the AIS and the electrode affects threshold levels while alignment of the electrode with the axon or dendritic parts of the RGC can result in lower thresholds, even if the distance to the cell remains the same. SIGNIFICANCE Intrinsic morphological features can influence activation thresholds with the AIS having the strongest influence. However, the combined influence remains limited and may not be large enough to allow for selective activation between different RGC types.
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Affiliation(s)
- Paul Werginz
- Institute for Analysis and Scientific Computing, Vienna University of Technology, Vienna, Austria. Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States of America. Author to whom any correspondence should be addressed
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20
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Muralidharan M, Guo T, Shivdasani MN, Tsai D, Fried S, Li L, Dokos S, Morley JW, Lovell NH. Neural activity of functionally different retinal ganglion cells can be robustly modulated by high-rate electrical pulse trains. J Neural Eng 2020; 17:045013. [DOI: 10.1088/1741-2552/ab9a97] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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21
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Lozano A, Suárez JS, Soto-Sánchez C, Garrigós J, Martínez-Alvarez JJ, Ferrández JM, Fernández E. Neurolight: A Deep Learning Neural Interface for Cortical Visual Prostheses. Int J Neural Syst 2020; 30:2050045. [DOI: 10.1142/s0129065720500458] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Visual neuroprosthesis, that provide electrical stimulation along several sites of the human visual system, constitute a potential tool for vision restoration for the blind. Scientific and technological progress in the fields of neural engineering and artificial vision comes with new theories and tools that, along with the dawn of modern artificial intelligence, constitute a promising framework for the further development of neurotechnology. In the framework of the development of a Cortical Visual Neuroprosthesis for the blind (CORTIVIS), we are now facing the challenge of developing not only computationally powerful tools and flexible approaches that will allow us to provide some degree of functional vision to individuals who are profoundly blind. In this work, we propose a general neuroprosthesis framework composed of several task-oriented and visual encoding modules. We address the development and implementation of computational models of the firing rates of retinal ganglion cells and design a tool — Neurolight — that allows these models to be interfaced with intracortical microelectrodes in order to create electrical stimulation patterns that can evoke useful perceptions. In addition, the developed framework allows the deployment of a diverse array of state-of-the-art deep-learning techniques for task-oriented and general image pre-processing, such as semantic segmentation and object detection in our system’s pipeline. To the best of our knowledge, this constitutes the first deep-learning-based system designed to directly interface with the visual brain through an intracortical microelectrode array. We implement the complete pipeline, from obtaining a video stream to developing and deploying task-oriented deep-learning models and predictive models of retinal ganglion cells’ encoding of visual inputs under the control of a neurostimulation device able to send electrical train pulses to a microelectrode array implanted at the visual cortex.
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Affiliation(s)
- Antonio Lozano
- Departamento de Electrónica, Tecnología de Computadoras y Proyectos, Universidad Politécnica de Cartagena, 30202 Cartagena, Spain
| | - Juan Sebastián Suárez
- Instituto de Bioingeniería, Universidad Miguel Hernández, 03202 Alicante, Spain
- CIBER-BBN, 28029 Madrid, Spain
| | - Cristina Soto-Sánchez
- Instituto de Bioingeniería, Universidad Miguel Hernández, 03202 Alicante, Spain
- CIBER-BBN, 28029 Madrid, Spain
| | - Javier Garrigós
- Departamento de Electrónica, Tecnología de Computadoras y Proyectos, Universidad Politécnica de Cartagena, 30202 Cartagena, Spain
| | - J. Javier Martínez-Alvarez
- Departamento de Electrónica, Tecnología de Computadoras y Proyectos, Universidad Politécnica de Cartagena, 30202 Cartagena, Spain
| | - J. Manuel Ferrández
- Departamento de Electrónica, Tecnología de Computadoras y Proyectos, Universidad Politécnica de Cartagena, 30202 Cartagena, Spain
| | - Eduardo Fernández
- Instituto de Bioingeniería, Universidad Miguel Hernández, 03202 Alicante, Spain
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22
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Tong W, Hejazi M, Garrett DJ, Esler T, Prawer S, Meffin H, Ibbotson MR. Minimizing axon bundle activation of retinal ganglion cells with oriented rectangular electrodes. J Neural Eng 2020; 17:036016. [PMID: 32375131 DOI: 10.1088/1741-2552/ab909e] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Retinal prostheses aim to restore vision in patients with retinal degenerative diseases, such as age-related macular degeneration and retinitis pigmentosa. By implanting an array of microelectrodes, such a device creates percepts in patients through electrical stimulation of surviving retinal neurons. A challenge for retinal prostheses when trying to return high quality vision is the unintended activation of retinal ganglion cells through the stimulation of passing axon bundles, which leads to patients reporting large, elongated patches of light instead of focal spots. APPROACH In this work, we used calcium imaging to record the responses of retinal ganglion cells to electrical stimulation in explanted retina using rectangular electrodes placed with different orientations relative to the axon bundles. MAIN RESULTS We showed that narrow, rectangular electrodes oriented parallel to the axon bundles can achieve focal stimulation. To further improve the strategy, we studied the impact of different stimulation waveforms and electrode configurations. We found the selectivity for focal stimulation to be higher when using short (33 μs), anodic-first biphasic pulses, with long electrode lengths and at least 50 μm electrode-to-retinal separation. Focal stimulation was, in fact, less selective when the electrodes made direct contact with the retinal surface due to unwanted preferential stimulation of the proximal axon bundles. SIGNIFICANCE When employed in retinal prostheses, the proposed stimulation strategy is expected to provide improved quality of vision to the blind.
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Affiliation(s)
- Wei Tong
- National Vision Research Institute, Australian College of Optometry, Carlton, VIC, Australia. School of Physics, The University of Melbourne, Parkville, VIC, Australia. Department of Vision Science and Optometry, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC, Australia
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23
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Kosta P, Loizos K, Lazzi G. Stimulus waveform design for decreasing charge and increasing stimulation selectivity in retinal prostheses. Healthc Technol Lett 2020; 7:66-71. [PMID: 32754340 PMCID: PMC7353818 DOI: 10.1049/htl.2019.0115] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Revised: 05/04/2020] [Accepted: 05/12/2020] [Indexed: 02/03/2023] Open
Abstract
Retinal degenerative diseases, such as retinitis pigmentosa, begin with damage to the photoreceptor layer of the retina. In the absence of presynaptic input from photoreceptors, networks of electrically coupled AII amacrine and cone bipolar cells have been observed to exhibit oscillatory behaviour and result in spontaneous firing of ganglion cells. This ganglion cell activity could interfere with external stimuli provided by retinal prosthetic devices and potentially degrade their performance. In this work, the authors computationally investigate stimulus waveform designs, which can improve the performance of retinal prostheses by suppressing undesired spontaneous firing of ganglion cells and generating precise temporal spiking patterns. They utilise a multi-scale computational model for electrical stimulation of degenerated retina based on the admittance method and NEURON simulation environments. They present a class of asymmetric biphasic pulses that can generate precise ganglion cell firing patterns with up to 55% lower current requirements compared to traditional symmetric biphasic pulses. This lower current results in activation of only proximal ganglion cells, provides more focused stimulation and lowers the risk of tissue damage.
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Affiliation(s)
- Pragya Kosta
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112, USA
| | - Kyle Loizos
- Department of Electrical Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Gianluca Lazzi
- Department of Electrical Engineering, University of Southern California, Los Angeles, CA 90089, USA.,Department of Ophthalmology, University of Southern California, Los Angeles, CA 90033, USA
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24
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Im M, Kim SW. Neurophysiological and medical considerations for better-performing microelectronic retinal prostheses. J Neural Eng 2020; 17:033001. [PMID: 32329755 DOI: 10.1088/1741-2552/ab8ca9] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Maesoon Im
- Center for BioMicrosystems, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea. Division of Bio-Medical Science & Technology, KIST School, University of Science and Technology (UST), Seoul, Republic of Korea
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The Roles of an Aluminum Underlayer in the Biocompatibility and Mechanical Integrity of Vertically Aligned Carbon Nanotubes for Interfacing with Retinal Neurons. MICROMACHINES 2020; 11:mi11060546. [PMID: 32481670 PMCID: PMC7345717 DOI: 10.3390/mi11060546] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 05/22/2020] [Accepted: 05/26/2020] [Indexed: 02/06/2023]
Abstract
Retinal implant devices are becoming an increasingly realizable way to improve the vision of patients blinded by photoreceptor degeneration. As an electrode material that can improve restored visual acuity, carbon nanotubes (CNTs) excel due to their nanoscale topography, flexibility, surface chemistry, and double-layer capacitance. If vertically aligned carbon nanotubes (VACNTs) are biocompatible with retinal neurons and mechanically robust, they can further improve visual acuity-most notably in subretinal implants-because they can be patterned into high-aspect-ratio, micrometer-size electrodes. We investigated the role of an aluminum (Al) underlayer beneath an iron (Fe) catalyst layer used in the growth of VACNTs by chemical vapor deposition (CVD). In particular, we cultured dissociated retinal cells for three days in vitro (DIV) on unfunctionalized and oxygen plasma functionalized VACNTs grown from a Fe catalyst (Fe and Fe + Pl preparations, where Pl signifies the plasma functionalization) and an Fe catalyst with an Al underlayer (Al/Fe and Al/Fe + Pl preparations). The addition of the Al layer increased the mechanical integrity of the VACNT interface and enhanced retinal neurite outgrowth over the Fe preparation. Unexpectedly, the extent of neurite outgrowth was significantly greater in the Al/Fe than in the Al/Fe+Pl preparation, suggesting plasma functionalization can negatively impact biocompatibility for some VACNT preparations. Additionally, we show our VACNT growth process for the Al/Fe preparation can support neurite outgrowth for up to 7 DIV. By demonstrating the retinal neuron biocompatibility, mechanical integrity, and pattern control of our VACNTs, this work offers VACNT electrodes as a solution for improving the restored visual acuity provided by modern retinal implants.
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Tong W, Meffin H, Garrett DJ, Ibbotson MR. Stimulation Strategies for Improving the Resolution of Retinal Prostheses. Front Neurosci 2020; 14:262. [PMID: 32292328 PMCID: PMC7135883 DOI: 10.3389/fnins.2020.00262] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 03/09/2020] [Indexed: 12/17/2022] Open
Abstract
Electrical stimulation using implantable devices with arrays of stimulating electrodes is an emerging therapy for neurological diseases. The performance of these devices depends greatly on their ability to activate populations of neurons with high spatiotemporal resolution. To study electrical stimulation of populations of neurons, retina serves as a useful model because the neural network is arranged in a planar array that is easy to access. Moreover, retinal prostheses are under development to restore vision by replacing the function of damaged light sensitive photoreceptors, which makes retinal research directly relevant for curing blindness. Here we provide a progress review on stimulation strategies developed in recent years to improve the resolution of electrical stimulation in retinal prostheses. We focus on studies performed with explanted retinas, in which electrophysiological techniques are the most advanced. We summarize achievements in improving the spatial and temporal resolution of electrical stimulation of the retina and methods to selectively stimulate neurons with different visual functions. Future directions for retinal prostheses development are also discussed, which could provide insights for other types of neuromodulatory devices in which high-resolution electrical stimulation is required.
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Affiliation(s)
- Wei Tong
- National Vision Research Institute, Australian College of Optometry, Carlton, VIC, Australia
- Department of Optometry and Vision Sciences, Melbourne School of Health Sciences, The University of Melbourne, Melbourne, VIC, Australia
- School of Physics, The University of Melbourne, Melbourne, VIC, Australia
| | - Hamish Meffin
- National Vision Research Institute, Australian College of Optometry, Carlton, VIC, Australia
- Department of Optometry and Vision Sciences, Melbourne School of Health Sciences, The University of Melbourne, Melbourne, VIC, Australia
- Department of Biomedical Engineering, The University of Melbourne, Melbourne, VIC, Australia
| | - David J. Garrett
- School of Physics, The University of Melbourne, Melbourne, VIC, Australia
| | - Michael R. Ibbotson
- National Vision Research Institute, Australian College of Optometry, Carlton, VIC, Australia
- Department of Optometry and Vision Sciences, Melbourne School of Health Sciences, The University of Melbourne, Melbourne, VIC, Australia
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27
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An update on retinal prostheses. Clin Neurophysiol 2019; 131:1383-1398. [PMID: 31866339 DOI: 10.1016/j.clinph.2019.11.029] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 11/13/2019] [Accepted: 11/14/2019] [Indexed: 11/23/2022]
Abstract
Retinal prostheses are designed to restore a basic sense of sight to people with profound vision loss. They require a relatively intact posterior visual pathway (optic nerve, lateral geniculate nucleus and visual cortex). Retinal implants are options for people with severe stages of retinal degenerative disease such as retinitis pigmentosa and age-related macular degeneration. There have now been three regulatory-approved retinal prostheses. Over five hundred patients have been implanted globally over the past 15 years. Devices generally provide an improved ability to localize high-contrast objects, navigate, and perform basic orientation tasks. Adverse events have included conjunctival erosion, retinal detachment, loss of light perception, and the need for revision surgery, but are rare. There are also specific device risks, including overstimulation (which could cause damage to the retina) or delamination of implanted components, but these are very unlikely. Current challenges include how to improve visual acuity, enlarge the field-of-view, and reduce a complex visual scene to its most salient components through image processing. This review encompasses the work of over 40 individual research groups who have built devices, developed stimulation strategies, or investigated the basic physiology underpinning retinal prostheses. Current technologies are summarized, along with future challenges that face the field.
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Raghuram V, Werginz P, Fried SI. Scaling of the AIS and Somatodendritic Compartments in α S RGCs. Front Cell Neurosci 2019; 13:436. [PMID: 31611777 PMCID: PMC6777007 DOI: 10.3389/fncel.2019.00436] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 09/13/2019] [Indexed: 11/21/2022] Open
Abstract
The anatomical properties of the axon initial segment (AIS) are tailored in certain types of CNS neurons to help optimize different aspects of neuronal function. Here, we questioned whether the AISs of retinal ganglion cells (RGC) were similarly customized, and if so, whether they supported specific RGC functions. To explore this, we measured the AIS properties in alpha sustained RGCs (α S RGCs) of mouse; α S RGCs sizes vary systematically along the nasal temporal axis of the retina, making these cells an attractive population with which to study potential correlations between AIS properties and cell size. Measurements of AIS length as well as distance from the soma revealed that both were scaled to cell size, i.e., cells with large dendritic fields had long AISs that were relatively far from the soma. Within the AIS, the percentage of Na v 1.6 voltage-gated sodium channels remained highly consistent, regardless of cell size or other AIS properties. Although ON RGCs were slightly larger than OFF cells at any given location of the retina, the level of scaling and relative distribution of voltage-gated sodium channels were highly similar. Computational modeling revealed that AIS scaling influenced spiking thresholds, spike rate as well as the kinetics of individual action potentials, Interestingly, the effect of individual features of the AIS varied for different neuronal functions, e.g., AIS length had a larger effect on the efficacy by which the AIS initiated spike triggered the somatic spike than it did on repetitive spiking. The polarity of the effect varied for different properties, i.e., increases to soma size increased spike threshold while increases to AIS length decreased threshold. Thus, variations in the relative level of scaling for individual components could fine tune threshold or other neuronal functions. Light responses were highly consistent across the full range of cell sizes suggesting that scaling may post-synaptically shape response stability, e.g., in addition to several well-known pre-synaptic contributors.
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Affiliation(s)
- Vineeth Raghuram
- Rehabilitation Research & Development Service, Boston VA Healthcare System, Boston, MA, United States
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
- Department of Biomedical Engineering, Tufts University, Medford, MA, United States
| | - Paul Werginz
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
- Institute for Analysis and Scientific Computing, Vienna University of Technology, Vienna, Austria
| | - Shelley I. Fried
- Rehabilitation Research & Development Service, Boston VA Healthcare System, Boston, MA, United States
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
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Lee JI, Im M. Optimal Electric Stimulus Amplitude Improves the Selectivity Between Responses of ON Versus OFF Types of Retinal Ganglion Cells. IEEE Trans Neural Syst Rehabil Eng 2019; 27:2015-2024. [PMID: 31484127 DOI: 10.1109/tnsre.2019.2939012] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Outer retinal degenerative diseases destroy photoreceptors primarily in the retina, resulting in a profound vision loss. Fortunately, surviving retinal neurons can be electrically stimulated using retinal prostheses to re-transmit visual information. Although retinal prostheses are promising for sight restoration, the best performance is still sub-optimal. For the enhanced performance, it is critical to optimize stimulation parameters. This study explored how stimulus charge and current amplitude alters responses of retinal ganglion cells (RGCs). From the isolated mouse retina, spiking activities of alpha ON, OFF sustained, and OFF transient RGCs were recorded in response to epiretinally-delivered cathodal current pulses ranging from -10 to [Formula: see text]. We have found that intermediate current amplitudes (-30 and [Formula: see text]) maximize the response ratio of ON over OFF types. Also, the ON/OFF response ratio was always bigger for 10-ms-long than 5-ms-long stimuli. It was because, by the longer pulses, ON RGC responses were always significantly enhanced ( ) while OFF RGC responses were minimally changed ( ). Given the earlier work reporting electrically-elicited responses are more natural in ON than OFF RGCs, the present study suggests effect strategies of more selective activation of ON RGCs for improved efficacy of retinal implant.
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Ryu SB, Werginz P, Fried SI. Response of Mouse Visual Cortical Neurons to Electric Stimulation of the Retina. Front Neurosci 2019; 13:324. [PMID: 31019449 PMCID: PMC6459047 DOI: 10.3389/fnins.2019.00324] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 03/21/2019] [Indexed: 12/27/2022] Open
Abstract
Retinal prostheses strive to restore vision to the blind by electrically stimulating the neurons that survive the disease process. Clinical effectiveness has been limited however, and much ongoing effort is devoted toward the development of improved stimulation strategies, especially ones that better replicate physiological patterns of neural signaling. Here, to better understand the potential effectiveness of different stimulation strategies, we explore the responses of neurons in the primary visual cortex to electric stimulation of the retina. A 16-channel implantable microprobe was used to record single unit activities in vivo from each layer of the mouse visual cortex. Layers were identified by electrode depth as well as spontaneous rate. Cell types were classified as excitatory or inhibitory based on their spike waveform and as ON, OFF, or ON-OFF based on the polarity of their light response. After classification, electric stimulation was delivered via a wire electrode placed on the surface of cornea (extraocularly) and responses were recorded from the cortex contralateral to the stimulated eye. Responses to electric stimulation were highly similar across cell types and layers. Responses (spike counts) increased as a function of the amplitude of stimulation, and although there was some variance across cells, the sensitivity to amplitude was largely similar across all cell types. Suppression of responses was observed for pulse rates ≥3 pulses per second (PPS) but did not originate in the retina as RGC responses remained stable to rates up to 5 PPS. Low-frequency sinusoids delivered to the retina replicated the out-of-phase responses that occur naturally in ON vs. OFF RGCs. Intriguingly, out-of-phase signaling persisted in V1 neurons, suggesting key aspects of neural signaling are preserved during transmission along visual pathways. Our results describe an approach to evaluate responses of cortical neurons to electric stimulation of the retina. By examining the responses of single cells, we were able to show that some retinal stimulation strategies can indeed better match the neural signaling patterns used by the healthy visual system. Because cortical signaling is better correlated to psychophysical percepts, the ability to evaluate which strategies produce physiological-like cortical responses may help to facilitate better clinical outcomes.
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Affiliation(s)
- Sang Baek Ryu
- Boston VA Healthcare System, Boston, MA, United States.,Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
| | - Paul Werginz
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States.,Institute for Analysis and Scientific Computing, Vienna University of Technology, Vienna, Austria
| | - Shelley I Fried
- Boston VA Healthcare System, Boston, MA, United States.,Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
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Chang YC, Haji Ghaffari D, Chow RH, Weiland JD. Stimulation strategies for selective activation of retinal ganglion cell soma and threshold reduction. J Neural Eng 2019; 16:026017. [PMID: 30560810 PMCID: PMC6648650 DOI: 10.1088/1741-2552/aaf92b] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
OBJECTIVE Retinal prosthetic implants restore partial vision to patients blinded due to outer retinal degeneration, using a camera-guided multielectrode array (MEA) that electrically stimulates surviving retinal neurons. Commercial epi-retinal prostheses use millisecond-scale charge-balanced, symmetric, cathodic-first biphasic pulses to depolarize retinal ganglion cells (RGCs) and bipolar cells (BCs), frequently creating oblong perceptions of light related to axonal activation of RGCs. Stimulation strategies that avoid axonal stimulation and decrease the threshold of targeted neurons may significantly improve prosthetic vision in terms of spatial resolution and power efficiency. APPROACH We developed a virus-transduced genetically encoded calcium indicator (GECI) GCaMP6f and microscopy platform for calcium imaging to record the neural activity from RGCs at single-cell resolution in wholemount retinas. Multiple stimulation paradigms were applied through a microelectrode array (MEA) with transparent indium tin oxide electrodes. The evoked neuronal activities were converted to corresponding 2D calcium imaging transient pattern and spatial threshold map to identify the ideal focal response which corresponds to optimal percept in patient. MAIN RESULTS The proposed optical system with GCaMP6f is capable of recording from population of mouse RGCs in real time during electrical stimulation with precise location information relative to the stimulation sites. Optimal duration and phase order of pulse were identified to avoid axonal stimulation and selectively activate targeted RGC somas, without requiring a significant increase in stimulation charge. Additionally, we show that reduced stimulus threshold can be achieved with the special design of asymmetric anodic-first pulse. SIGNIFICANCE Our findings support the possibility of manipulating the responses of RGCs through varying the stimulation waveform. Focal response can be achieved with relative short duration (⩽120 μs) pulses, and can be improved by reversing the standard phase order. The RGCs threshold can be significantly reduced by 33.3%-50% in terms of charge through applying hyperpolarizing pre-pulses with a 20:1 ratio (pre-pulse:stimulus pulse). The results support the future retinal prosthesis design that potentially forms more ideal shape perception with higher spatial resolution and power efficiency.
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Affiliation(s)
- Yao-Chuan Chang
- Center for Bioelectronic Medicine & Biomedical Science, Feinstein Institute for Medical Research, Manhasset, NY 11030, United States of America
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32
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Spencer MJ, Kameneva T, Grayden DB, Meffin H, Burkitt AN. Global activity shaping strategies for a retinal implant. J Neural Eng 2019; 16:026008. [DOI: 10.1088/1741-2552/aaf071] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Fan VH, Grosberg LE, Madugula SS, Hottowy P, Dabrowski W, Sher A, Litke AM, Chichilnisky EJ. Epiretinal stimulation with local returns enhances selectivity at cellular resolution. J Neural Eng 2018; 16:025001. [PMID: 30523958 DOI: 10.1088/1741-2552/aaeef1] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Epiretinal prostheses are designed to restore vision in people blinded by photoreceptor degenerative diseases, by directly activating retinal ganglion cells (RGCs) using an electrode array implanted on the retina. In present-day clinical devices, current spread from the stimulating electrode to a distant return electrode often results in the activation of many cells, potentially limiting the quality of artificial vision. In the laboratory, epiretinal activation of RGCs with cellular resolution has been demonstrated with small electrodes, but distant returns may still cause undesirable current spread. Here, the ability of local return stimulation to improve the selective activation of RGCs at cellular resolution was evaluated. APPROACH A custom multi-electrode array (512 electrodes, 10 μm diameter, 60 μm pitch) was used to simultaneously stimulate and record from RGCs in isolated primate retina. Stimulation near the RGC soma with a single electrode and a distant return was compared to stimulation in which the return was provided by six neighboring electrodes. MAIN RESULTS Local return stimulation enhanced the capability to activate cells near the central electrode (<30 μm) while avoiding cells farther away (>30 μm). This resulted in an improved ability to selectively activate ON and OFF cells, including cells encoding immediately adjacent regions in the visual field. SIGNIFICANCE These results suggest that a device that restricts the electric field through local returns could optimize activation of neurons at cellular resolution, improving the quality of artificial vision.
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Affiliation(s)
- Victoria H Fan
- Departments of Neurosurgery, Ophthalmology, and Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
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Fried SI. Network-mediated responses of ON ganglion cells to electric stimulation become less consistent across trials during retinal degeneration. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2018; 2017:2114-2117. [PMID: 29060314 DOI: 10.1109/embc.2017.8037271] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Microelectronic retinal prostheses are being developed to restore sight in individuals blinded by outer retinal degenerative diseases such as retinitis pigmentosa and age-related macular degeneration. Unfortunately, the quality of vision restored by these devices is still limited. To improve the quality of elicited vision, our group studies the responses of retinal neurons to electric stimulation. Our previous work showed that responses mediated through the retinal network are reproducible with high temporal precision, even for spikes that occur >100 ms after stimulus onset. Because they arise through the network, it is important to understand whether such reliability changes in the degenerate retina. Here, we examined response variability at several different stages of degeneration: postnatal day 14 (P14), P18, P31 and P60 in a well-established mouse model of degeneration (rd10). Spiking responses of ON alpha RGCs were recorded multiple times to an identical electric stimulus. We found that the trial-to-trial variability increased over the course of retinal degeneration. This finding may help to explain the reported variability in the quality of elicited vision across subjects using these devices.
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Lee JI, Im M. Non-rectangular waveforms are more charge-efficient than rectangular one in eliciting network-mediated responses of ON type retinal ganglion cells. J Neural Eng 2018; 15:055004. [PMID: 30018183 DOI: 10.1088/1741-2552/aad416] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE For individuals blinded by outer retinal degenerative diseases, retinal prostheses would be a promising option to restore sight. Unfortunately, however, the best performance of existing devices is still far removed from normal vision. One possible reason for the shortcoming is thought to be suboptimal stimulation conditions such as the waveform shape of electric stimulus. In this study, we explored the effects of varying waveforms on network-mediated responses arising in retinal ganglion cells (RGCs). APPROACH We used a cell-attached patch clamp technique to record RGC spiking activities in the isolated mouse retina. ON alpha RGCs were targeted by soma size and their light responses to stationary spot flashes. Spiking in targeted RGCs was measured in response to an epiretinally-delivered cathodal current pulse in four waveforms: rectangular, center triangular, increasing and decreasing ramp shapes. Each waveform was tested at three durations (20, 10, and 5 ms) with adjusted amplitude for a range of total charges (50-400 nC). MAIN RESULTS ON alpha RGCs always generated two bursts of spikes in responses to all stimuli conditions we tested. However, at a given charge, effects of differing waveforms were distinct in the two bursts. For the first burst, the increasing ramp was most effective among the four waveforms (p < 0.05 for all pairwise comparisons with other waveforms). For example, in responses arising from 20 ms-long stimuli, the increasing ramp evoked ~44% more spikes on average than the rectangular shape which is the typical choice of neural stimulation. Also, the rectangular stimulus evoked the weakest response in the delayed burst arising from pulses of every duration. For instance, 20 ms-long stimuli in the three non-rectangular waveforms showed ~23% or more increment in spike counts compared to response arising from the rectangular one; but there was no statistical difference in response magnitudes across the non-rectangular waveforms. SIGNIFICANCE Although the rectangular waveform has been primarily used in retinal prostheses our results indicate that rectangular stimulus is not optimal for network-mediated responses of ON alpha RGCs. Instead, non-rectangular waveforms evoke stronger responses at a given charge, indicating higher charge-efficiency. Therefore, non-rectangular waveforms are expected to enhance clinical efficacy of retinal prostheses.
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Affiliation(s)
- Jae-Ik Lee
- Department of Ophthalmology, Henry Ford Health System, 1 Ford Place, Detroit, MI 48202, United States of America. Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114, United States of America
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Mardinly AR, Oldenburg IA, Pégard NC, Sridharan S, Lyall EH, Chesnov K, Brohawn SG, Waller L, Adesnik H. Precise multimodal optical control of neural ensemble activity. Nat Neurosci 2018; 21:881-893. [PMID: 29713079 PMCID: PMC5970968 DOI: 10.1038/s41593-018-0139-8] [Citation(s) in RCA: 147] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 03/22/2018] [Indexed: 12/16/2022]
Abstract
Understanding brain function requires technologies that can control the activity of large populations of neurons with high fidelity in space and time. We developed a multiphoton holographic approach to activate or suppress the activity of ensembles of cortical neurons with cellular resolution and sub-millisecond precision. Since existing opsins were inadequate, we engineered new soma-targeted (ST) optogenetic tools, ST-ChroME and IRES-ST-eGtACR1, optimized for multiphoton activation and suppression. Employing a three-dimensional all-optical read-write interface, we demonstrate the ability to simultaneously photostimulate up to 50 neurons distributed in three dimensions in a 550 × 550 × 100-µm3 volume of brain tissue. This approach allows the synthesis and editing of complex neural activity patterns needed to gain insight into the principles of neural codes.
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Affiliation(s)
- Alan R Mardinly
- Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Ian Antón Oldenburg
- Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Nicolas C Pégard
- Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, CA, USA
- Department of Electrical Engineering & Computer Sciences, University of California, Berkeley, Berkeley, CA, USA
| | - Savitha Sridharan
- Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Evan H Lyall
- Biophysics Graduate Group, University of California, Berkeley, Berkeley, CA, USA
| | - Kirill Chesnov
- Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Stephen G Brohawn
- Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, CA, USA
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, USA
| | - Laura Waller
- Department of Electrical Engineering & Computer Sciences, University of California, Berkeley, Berkeley, CA, USA
| | - Hillel Adesnik
- Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, CA, USA.
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, USA.
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37
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Im M, Werginz P, Fried SI. Electric stimulus duration alters network-mediated responses depending on retinal ganglion cell type. J Neural Eng 2018; 15:036010. [PMID: 29415876 DOI: 10.1088/1741-2552/aaadc1] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
OBJECTIVE To improve the quality of artificial vision that arises from retinal prostheses, it is important to bring electrically-elicited neural activity more in line with the physiological signaling patterns that arise normally in the healthy retina. Our previous study reported that indirect activation produces a closer match to physiological responses in ON retinal ganglion cells (RGCs) than in OFF cells (Im and Fried 2015 J. Physiol. 593 3677-96). This suggests that a preferential activation of ON RGCs would shape the overall retinal response closer to natural signaling. Recently, we found that changes to the rate at which stimulation was delivered could bias responses towards a stronger ON component (Im and Fried 2016a J. Neural Eng. 13 025002), raising the possibility that changes to other stimulus parameters can similarly bias towards stronger ON responses. Here, we explore the effects of changing stimulus duration on the responses in ON and OFF types of brisk transient (BT) and brisk sustained (BS) RGCs. APPROACH We used cell-attached patch clamp to record RGC spiking in the isolated rabbit retina. Targeted RGCs were first classified as ON or OFF type by their light responses, and further sub-classified as BT or BS types by their responses to both light and electric stimuli. Spiking in targeted RGCs was recorded in response to electric pulses with durations varying from 5 to100 ms. Stimulus amplitude was adjusted at each duration to hold total charge constant for all experiments. MAIN RESULTS We found that varying stimulus durations modulated responses differentially for ON versus OFF cells: in ON cells, spike counts decreased significantly with increasing stimulus duration while in OFF cells the changes were more modest. The maximum ratio of ON versus OFF responses occurred at a duration of ~10 ms. The difference in response strength for BT versus BS cells was much larger in ON cells than in OFF cells. SIGNIFICANCE The stimulation rates preferred by subjects during clinical trials are similar to the rates that maximize the ON/OFF response ratio in in vitro testing (Im and Fried 2016a J. Neural Eng. 13 025002). Here, we determine the stimulus duration that produces the strongest bias towards ON responses and speculate that it will further enhance clinical effectiveness.
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Affiliation(s)
- Maesoon Im
- Department of Ophthalmology, Henry Ford Health System, 1 Ford Place, Detroit, MI 48202, United States of America. Department of Anatomy and Cell Biology, Wayne State University School of Medicine, 540 East Canfield Street, Detroit, MI 48201, United States of America. Department of Electrical and Computer Engineering, Wayne State University College of Engineering, 5050 Anthony Wayne Drive, Detroit, MI 48202, United States of America. Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, 50 Blossom Street, Boston, MA 02114, United States of America
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Mena GE, Grosberg LE, Madugula S, Hottowy P, Litke A, Cunningham J, Chichilnisky EJ, Paninski L. Electrical stimulus artifact cancellation and neural spike detection on large multi-electrode arrays. PLoS Comput Biol 2017; 13:e1005842. [PMID: 29131818 PMCID: PMC5703587 DOI: 10.1371/journal.pcbi.1005842] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 11/27/2017] [Accepted: 10/20/2017] [Indexed: 11/18/2022] Open
Abstract
Simultaneous electrical stimulation and recording using multi-electrode arrays can provide a valuable technique for studying circuit connectivity and engineering neural interfaces. However, interpreting these measurements is challenging because the spike sorting process (identifying and segregating action potentials arising from different neurons) is greatly complicated by electrical stimulation artifacts across the array, which can exhibit complex and nonlinear waveforms, and overlap temporarily with evoked spikes. Here we develop a scalable algorithm based on a structured Gaussian Process model to estimate the artifact and identify evoked spikes. The effectiveness of our methods is demonstrated in both real and simulated 512-electrode recordings in the peripheral primate retina with single-electrode and several types of multi-electrode stimulation. We establish small error rates in the identification of evoked spikes, with a computational complexity that is compatible with real-time data analysis. This technology may be helpful in the design of future high-resolution sensory prostheses based on tailored stimulation (e.g., retinal prostheses), and for closed-loop neural stimulation at a much larger scale than currently possible.
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Affiliation(s)
- Gonzalo E. Mena
- Statistics Department, Columbia University, New York, New York, United States of America
| | - Lauren E. Grosberg
- Department of Neurosurgery and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States of America
| | - Sasidhar Madugula
- Department of Neurosurgery and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States of America
| | - Paweł Hottowy
- Physics and Applied Computer Science, AGH University of Science and Technology, Krakow, Poland
| | - Alan Litke
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, Santa Cruz, California, United States of America
| | - John Cunningham
- Statistics Department, Columbia University, New York, New York, United States of America
- Grossman Center for the Statistics of Mind and Center for Theoretical Neuroscience, Columbia University, New York, New York, United States of America
| | - E. J. Chichilnisky
- Department of Neurosurgery and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States of America
| | - Liam Paninski
- Statistics Department, Columbia University, New York, New York, United States of America
- Grossman Center for the Statistics of Mind and Center for Theoretical Neuroscience, Columbia University, New York, New York, United States of America
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Tsai D, Morley JW, Suaning GJ, Lovell NH. Survey of electrically evoked responses in the retina - stimulus preferences and oscillation among neurons. Sci Rep 2017; 7:13802. [PMID: 29062068 PMCID: PMC5653866 DOI: 10.1038/s41598-017-14357-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 10/10/2017] [Indexed: 01/31/2023] Open
Abstract
Electrical stimulation is an important tool in neuroscience research and clinically. In the retina, extensive work has revealed how the retinal ganglion cells respond to extracellular electrical stimulation. But little is known about the responses of other neuronal types, and more generally, how the network responds to stimulation. We conducted a survey of electrically evoked responses, over a range of pulse amplitudes and pulse widths, for 21 cell types spanning the inner two layers of the rabbit retina. It revealed: (i) the evoked responses of some neurons were charge insensitive; (ii) pulse-width sensitivity varied between cell types, allowing preferential recruitment of cell types; and (iii) 10-20 Hz damped oscillations across retinal layers. These oscillations were generated by reciprocal excitatory / inhibitory synapses, at locations as early as the cone-horizontal-cell synapses. These results illustrate at cellular resolution how a network responds to extracellular stimulation, and could inform the development of bioelectronic implants for treating blindness.
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Affiliation(s)
- David Tsai
- Department of Electrical Engineering, Columbia University, New Yok, NY, USA.
- Graduate School of Biomedical Engineering, UNSW Australia, NSW, Australia.
| | - John W Morley
- School of Medicine, Western Sydney University, Sydney, NSW, Australia
- School of Medicine, UNSW Australia, NSW, Australia
| | - Gregg J Suaning
- Graduate School of Biomedical Engineering, UNSW Australia, NSW, Australia
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, UNSW Australia, NSW, Australia
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Grosberg LE, Ganesan K, Goetz GA, Madugula SS, Bhaskhar N, Fan V, Li P, Hottowy P, Dabrowski W, Sher A, Litke AM, Mitra S, Chichilnisky EJ. Activation of ganglion cells and axon bundles using epiretinal electrical stimulation. J Neurophysiol 2017; 118:1457-1471. [PMID: 28566464 DOI: 10.1152/jn.00750.2016] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 05/30/2017] [Accepted: 05/30/2017] [Indexed: 12/17/2022] Open
Abstract
Epiretinal prostheses for treating blindness activate axon bundles, causing large, arc-shaped visual percepts that limit the quality of artificial vision. Improving the function of epiretinal prostheses therefore requires understanding and avoiding axon bundle activation. This study introduces a method to detect axon bundle activation on the basis of its electrical signature and uses the method to test whether epiretinal stimulation can directly elicit spikes in individual retinal ganglion cells without activating nearby axon bundles. Combined electrical stimulation and recording from isolated primate retina were performed using a custom multielectrode system (512 electrodes, 10-μm diameter, 60-μm pitch). Axon bundle signals were identified by their bidirectional propagation, speed, and increasing amplitude as a function of stimulation current. The threshold for bundle activation varied across electrodes and retinas, and was in the same range as the threshold for activating retinal ganglion cells near their somas. In the peripheral retina, 45% of electrodes that activated individual ganglion cells (17% of all electrodes) did so without activating bundles. This permitted selective activation of 21% of recorded ganglion cells (7% of expected ganglion cells) over the array. In one recording in the central retina, 75% of electrodes that activated individual ganglion cells (16% of all electrodes) did so without activating bundles. The ability to selectively activate a subset of retinal ganglion cells without axon bundles suggests a possible novel architecture for future epiretinal prostheses.NEW & NOTEWORTHY Large-scale multielectrode recording and stimulation were used to test how selectively retinal ganglion cells can be electrically activated without activating axon bundles. A novel method was developed to identify axon activation on the basis of its unique electrical signature and was used to find that a subset of ganglion cells can be activated at single-cell, single-spike resolution without producing bundle activity in peripheral and central retina. These findings have implications for the development of advanced retinal prostheses.
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Affiliation(s)
- Lauren E Grosberg
- Department of Neurosurgery and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California;
| | - Karthik Ganesan
- Departments of Electrical Engineering and Computer Science, Stanford University, Stanford, California
| | - Georges A Goetz
- Department of Neurosurgery and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California
| | - Sasidhar S Madugula
- Department of Neurosurgery and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California
| | - Nandita Bhaskhar
- Departments of Electrical Engineering and Computer Science, Stanford University, Stanford, California
| | - Victoria Fan
- Department of Neurosurgery and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California
| | - Peter Li
- Systems Neurobiology Laboratories, Salk Institute for Biological Studies, La Jolla, California
| | - Pawel Hottowy
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Krakow, Poland; and
| | - Wladyslaw Dabrowski
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Krakow, Poland; and
| | - Alexander Sher
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, Santa Cruz, California
| | - Alan M Litke
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, Santa Cruz, California
| | - Subhasish Mitra
- Departments of Electrical Engineering and Computer Science, Stanford University, Stanford, California
| | - E J Chichilnisky
- Department of Neurosurgery and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California
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41
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O'Shea DJ, Trautmann E, Chandrasekaran C, Stavisky S, Kao JC, Sahani M, Ryu S, Deisseroth K, Shenoy KV. The need for calcium imaging in nonhuman primates: New motor neuroscience and brain-machine interfaces. Exp Neurol 2017; 287:437-451. [PMID: 27511294 PMCID: PMC5154795 DOI: 10.1016/j.expneurol.2016.08.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 06/19/2016] [Accepted: 08/04/2016] [Indexed: 01/08/2023]
Abstract
A central goal of neuroscience is to understand how populations of neurons coordinate and cooperate in order to give rise to perception, cognition, and action. Nonhuman primates (NHPs) are an attractive model with which to understand these mechanisms in humans, primarily due to the strong homology of their brains and the cognitively sophisticated behaviors they can be trained to perform. Using electrode recordings, the activity of one to a few hundred individual neurons may be measured electrically, which has enabled many scientific findings and the development of brain-machine interfaces. Despite these successes, electrophysiology samples sparsely from neural populations and provides little information about the genetic identity and spatial micro-organization of recorded neurons. These limitations have spurred the development of all-optical methods for neural circuit interrogation. Fluorescent calcium signals serve as a reporter of neuronal responses, and when combined with post-mortem optical clearing techniques such as CLARITY, provide dense recordings of neuronal populations, spatially organized and annotated with genetic and anatomical information. Here, we advocate that this methodology, which has been of tremendous utility in smaller animal models, can and should be developed for use with NHPs. We review here several of the key opportunities and challenges for calcium-based optical imaging in NHPs. We focus on motor neuroscience and brain-machine interface design as representative domains of opportunity within the larger field of NHP neuroscience.
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Affiliation(s)
- Daniel J O'Shea
- Neurosciences Program, Stanford University, Stanford, CA 94305, United States
| | - Eric Trautmann
- Neurosciences Program, Stanford University, Stanford, CA 94305, United States
| | | | - Sergey Stavisky
- Neurosciences Program, Stanford University, Stanford, CA 94305, United States
| | - Jonathan C Kao
- Department of Electrical Engineering, Stanford University, Stanford, CA 94305, United States
| | - Maneesh Sahani
- Department of Electrical Engineering, Stanford University, Stanford, CA 94305, United States; Gatsby Computational Neuroscience Unit, University College London, London W1T 4JG, United Kingdom
| | - Stephen Ryu
- Department of Electrical Engineering, Stanford University, Stanford, CA 94305, United States; Department of Neurosurgery, Palo Alto Medical Foundation, Palo Alto, CA 94301, United States
| | - Karl Deisseroth
- Department of Bioengineering, Stanford University, Stanford, CA 94305, United States; Department of Psychiatry and Behavioral Science, Stanford University, Stanford, CA 94305, United States; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, United States
| | - Krishna V Shenoy
- Department of Electrical Engineering, Stanford University, Stanford, CA 94305, United States; Department of Bioengineering, Stanford University, Stanford, CA 94305, United States; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, United States; Deparment of Neurobiology, Stanford University, Stanford, CA 94305, United States.
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42
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Robust Functionalization of Large Microelectrode Arrays by Using Pulsed Potentiostatic Deposition. SENSORS 2016; 17:s17010022. [PMID: 28025569 PMCID: PMC5298595 DOI: 10.3390/s17010022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 12/13/2016] [Accepted: 12/21/2016] [Indexed: 11/17/2022]
Abstract
Surface modification of microelectrodes is a central step in the development of microsensors and microsensor arrays. Here, we present an electrodeposition scheme based on voltage pulses. Key features of this method are uniformity in the deposited electrode coatings, flexibility in the overall deposition area, i.e., the sizes and number of the electrodes to be coated, and precise control of the surface texture. Deposition and characterization of four different materials are demonstrated, including layers of high-surface-area platinum, gold, conducting polymer poly(ethylenedioxythiophene), also known as PEDOT, and the non-conducting polymer poly(phenylenediamine), also known as PPD. The depositions were conducted using a fully integrated complementary metal-oxide-semiconductor (CMOS) chip with an array of 1024 microelectrodes. The pulsed potentiostatic deposition scheme is particularly suitable for functionalization of individual electrodes or electrode subsets of large integrated microelectrode arrays: the required deposition waveforms are readily available in an integrated system, the same deposition parameters can be used to functionalize the surface of either single electrodes or large arrays of thousands of electrodes, and the deposition method proved to be robust and reproducible for all materials tested.
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43
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Sengupta A, Chaffiol A, Macé E, Caplette R, Desrosiers M, Lampič M, Forster V, Marre O, Lin JY, Sahel JA, Picaud S, Dalkara D, Duebel J. Red-shifted channelrhodopsin stimulation restores light responses in blind mice, macaque retina, and human retina. EMBO Mol Med 2016; 8:1248-1264. [PMID: 27679671 PMCID: PMC5090658 DOI: 10.15252/emmm.201505699] [Citation(s) in RCA: 113] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 08/09/2016] [Accepted: 08/11/2016] [Indexed: 01/31/2023] Open
Abstract
Targeting the photosensitive ion channel channelrhodopsin-2 (ChR2) to the retinal circuitry downstream of photoreceptors holds promise in treating vision loss caused by retinal degeneration. However, the high intensity of blue light necessary to activate channelrhodopsin-2 exceeds the safety threshold of retinal illumination because of its strong potential to induce photochemical damage. In contrast, the damage potential of red-shifted light is vastly lower than that of blue light. Here, we show that a red-shifted channelrhodopsin (ReaChR), delivered by AAV injections in blind rd1 mice, enables restoration of light responses at the retinal, cortical, and behavioral levels, using orange light at intensities below the safety threshold for the human retina. We further show that postmortem macaque retinae infected with AAV-ReaChR can respond with spike trains to orange light at safe intensities. Finally, to directly address the question of translatability to human subjects, we demonstrate for the first time, AAV- and lentivirus-mediated optogenetic spike responses in ganglion cells of the postmortem human retina.
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Affiliation(s)
- Abhishek Sengupta
- INSERM U968, Paris, France
- Sorbonne Universités UPMC Univ Paris 06 UMR_S 968 Institut de la Vision, Paris, France
- CNRS UMR_7210, Paris, France
| | - Antoine Chaffiol
- INSERM U968, Paris, France
- Sorbonne Universités UPMC Univ Paris 06 UMR_S 968 Institut de la Vision, Paris, France
- CNRS UMR_7210, Paris, France
| | - Emilie Macé
- INSERM U968, Paris, France
- Sorbonne Universités UPMC Univ Paris 06 UMR_S 968 Institut de la Vision, Paris, France
- CNRS UMR_7210, Paris, France
| | - Romain Caplette
- INSERM U968, Paris, France
- Sorbonne Universités UPMC Univ Paris 06 UMR_S 968 Institut de la Vision, Paris, France
- CNRS UMR_7210, Paris, France
| | - Mélissa Desrosiers
- INSERM U968, Paris, France
- Sorbonne Universités UPMC Univ Paris 06 UMR_S 968 Institut de la Vision, Paris, France
- CNRS UMR_7210, Paris, France
| | - Maruša Lampič
- INSERM U968, Paris, France
- Sorbonne Universités UPMC Univ Paris 06 UMR_S 968 Institut de la Vision, Paris, France
- CNRS UMR_7210, Paris, France
| | - Valérie Forster
- INSERM U968, Paris, France
- Sorbonne Universités UPMC Univ Paris 06 UMR_S 968 Institut de la Vision, Paris, France
- CNRS UMR_7210, Paris, France
| | - Olivier Marre
- INSERM U968, Paris, France
- Sorbonne Universités UPMC Univ Paris 06 UMR_S 968 Institut de la Vision, Paris, France
- CNRS UMR_7210, Paris, France
| | - John Y Lin
- School of Medicine, University of Tasmania, Hobart, Tasmania, Australia
| | - José-Alain Sahel
- INSERM U968, Paris, France
- Sorbonne Universités UPMC Univ Paris 06 UMR_S 968 Institut de la Vision, Paris, France
- CNRS UMR_7210, Paris, France
- Hôpital des Quinze-Vingts, Paris, France
| | - Serge Picaud
- INSERM U968, Paris, France
- Sorbonne Universités UPMC Univ Paris 06 UMR_S 968 Institut de la Vision, Paris, France
- CNRS UMR_7210, Paris, France
| | - Deniz Dalkara
- INSERM U968, Paris, France
- Sorbonne Universités UPMC Univ Paris 06 UMR_S 968 Institut de la Vision, Paris, France
- CNRS UMR_7210, Paris, France
| | - Jens Duebel
- INSERM U968, Paris, France
- Sorbonne Universités UPMC Univ Paris 06 UMR_S 968 Institut de la Vision, Paris, France
- CNRS UMR_7210, Paris, France
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Weitz AC, Nanduri D, Behrend MR, Gonzalez-Calle A, Greenberg RJ, Humayun MS, Chow RH, Weiland JD. Improving the spatial resolution of epiretinal implants by increasing stimulus pulse duration. Sci Transl Med 2016; 7:318ra203. [PMID: 26676610 DOI: 10.1126/scitranslmed.aac4877] [Citation(s) in RCA: 128] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Retinal prosthetic implants are the only approved treatment for retinitis pigmentosa, a disease of the eye that causes blindness through gradual degeneration of photoreceptors. An array of microelectrodes triggered by input from a camera stimulates surviving retinal neurons, with each electrode acting as a pixel. Unintended stimulation of retinal ganglion cell axons causes patients to see large oblong shapes of light, rather than focal spots, making it difficult to perceive forms. To address this problem, we performed calcium imaging in isolated retinas and mapped the patterns of cells activated by different electrical stimulation protocols. We found that pulse durations two orders of magnitude longer than those typically used in existing implants stimulated inner retinal neurons while avoiding activation of ganglion cell axons, thus confining retinal responses to the site of the electrode. Multielectrode stimulation with 25-ms pulses can pattern letters on the retina corresponding to a Snellen acuity of 20/312. We validated our findings in a patient with an implanted epiretinal prosthesis by demonstrating that 25-ms pulses evoke focal spots of light.
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Affiliation(s)
- Andrew C Weitz
- Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Devyani Nanduri
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Matthew R Behrend
- Department of Electrical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Alejandra Gonzalez-Calle
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | | | - Mark S Humayun
- Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Robert H Chow
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA. Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
| | - James D Weiland
- Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA.
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45
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Goetz GA, Palanker DV. Electronic approaches to restoration of sight. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2016; 79:096701. [PMID: 27502748 PMCID: PMC5031080 DOI: 10.1088/0034-4885/79/9/096701] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Retinal prostheses are a promising means for restoring sight to patients blinded by the gradual atrophy of photoreceptors due to retinal degeneration. They are designed to reintroduce information into the visual system by electrically stimulating surviving neurons in the retina. This review outlines the concepts and technologies behind two major approaches to retinal prosthetics: epiretinal and subretinal. We describe how the visual system responds to electrical stimulation. We highlight major differences between direct encoding of the retinal output with epiretinal stimulation, and network-mediated response with subretinal stimulation. We summarize results of pre-clinical evaluation of prosthetic visual functions in- and ex vivo, as well as the outcomes of current clinical trials of various retinal implants. We also briefly review alternative, non-electronic, approaches to restoration of sight to the blind, and conclude by suggesting some perspectives for future advancement in the field.
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Affiliation(s)
- G A Goetz
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA. Neurosurgery, Stanford University, Stanford, CA 94305, USA
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46
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Roux S, Matonti F, Dupont F, Hoffart L, Takerkart S, Picaud S, Pham P, Chavane F. Probing the functional impact of sub-retinal prosthesis. eLife 2016; 5. [PMID: 27549126 PMCID: PMC4995098 DOI: 10.7554/elife.12687] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 07/07/2016] [Indexed: 11/27/2022] Open
Abstract
Retinal prostheses are promising tools for recovering visual functions in blind patients but, unfortunately, with still poor gains in visual acuity. Improving their resolution is thus a key challenge that warrants understanding its origin through appropriate animal models. Here, we provide a systematic comparison between visual and prosthetic activations of the rat primary visual cortex (V1). We established a precise V1 mapping as a functional benchmark to demonstrate that sub-retinal implants activate V1 at the appropriate position, scalable to a wide range of visual luminance, but with an aspect-ratio and an extent much larger than expected. Such distorted activation profile can be accounted for by the existence of two sources of diffusion, passive diffusion and activation of ganglion cells’ axons en passant. Reverse-engineered electrical pulses based on impedance spectroscopy is the only solution we tested that decreases the extent and aspect-ratio, providing a promising solution for clinical applications. DOI:http://dx.doi.org/10.7554/eLife.12687.001 One of the most common causes of blindness is a disorder called retinitis pigmentosa. In a healthy eye, the surface at the back of the eye – called the retina – contains cells called photoreceptors that detect light and convert it into electrical signals for the brain to process. In people with retinitis pigmentosa, these photoreceptor cells die off gradually, which leads to loss of vision. The only treatment available for retinitis pigmentosa is to have an artificial retina implanted into the eye. The artificial retina consists of an array of tiny electrodes, which take over from the damaged photoreceptors and generate electrical signals. The person with the implant perceives these electrical signals as bright flashes called “phosphenes”. However, the phosphenes are too large and imprecise to provide the person with vision that is good enough for tasks such as walking unaided or reading. To find out why artificial retinas produce such poor resolution, Roux et al. compared how a rat’s brain responds to either natural visual stimuli or activation of implanted an array of micro-electrodes. Both the micro-electrodes and the natural stimuli activated the same areas of the brain. However, the micro-electrodes produced larger and more elongated patterns of activation. This is because the electrical currents generated by the micro-electrodes diffused throughout the retinal tissue and activated other neurons besides those intended. To overcome this problem, Roux et al. tested different ways of stimulating the micro-electrodes in order to identify those that induce the desired patterns of brain activity. This approach – known as reverse engineering – did indeed improve the performance of the micro-electrode array. The next step is to extend these findings, which were obtained in healthy rats, to non-human primates or animal models of retinitis pigmentosa to better understand the condition in humans. In addition, combining the current approach with other existing techniques should further improve the vision that can be achieved with artificial retinas. DOI:http://dx.doi.org/10.7554/eLife.12687.002
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Affiliation(s)
- Sébastien Roux
- Institut de Neurosciences de la Timone, CNRS, Aix-Marseille Université, Marseille, France
| | - Frédéric Matonti
- Institut de Neurosciences de la Timone, CNRS, Aix-Marseille Université, Marseille, France.,Ophthalmology Department, Aix Marseille Université, Hôpital Nord,Hôpital de la Timone, Marseille, France
| | - Florent Dupont
- CEA-LETI, Grenoble, France.,Université Grenoble Alpes, Grenoble, France
| | - Louis Hoffart
- Institut de Neurosciences de la Timone, CNRS, Aix-Marseille Université, Marseille, France.,Ophthalmology Department, Aix Marseille Université, Hôpital Nord,Hôpital de la Timone, Marseille, France
| | - Sylvain Takerkart
- Institut de Neurosciences de la Timone, CNRS, Aix-Marseille Université, Marseille, France
| | - Serge Picaud
- Inserm, UMRS-986, Institut de la vision, Paris, France
| | - Pascale Pham
- CEA-LETI, Grenoble, France.,Université Grenoble Alpes, Grenoble, France
| | - Frédéric Chavane
- Institut de Neurosciences de la Timone, CNRS, Aix-Marseille Université, Marseille, France
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47
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Yue L, Weiland JD, Roska B, Humayun MS. Retinal stimulation strategies to restore vision: Fundamentals and systems. Prog Retin Eye Res 2016; 53:21-47. [DOI: 10.1016/j.preteyeres.2016.05.002] [Citation(s) in RCA: 173] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 05/13/2016] [Accepted: 05/21/2016] [Indexed: 11/28/2022]
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48
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Abstract
OBJECTIVE High resolution visual prostheses require dense stimulating arrays with localized inputs of individual electrodes. We study the electric field produced by multielectrode arrays in electrolyte to determine an optimal configuration of return electrodes and activation sequence. APPROACH To determine the boundary conditions for computation of the electric field in electrolyte, we assessed current dynamics using an equivalent circuit of a multielectrode array with interleaved return electrodes. The electric field modeled with two different boundary conditions derived from the equivalent circuit was then compared to measurements of electric potential in electrolyte. To assess the effect of return electrode configuration on retinal stimulation, we transformed the computed electric fields into retinal response using a model of neural network-mediated stimulation. MAIN RESULTS Electric currents at the capacitive electrode-electrolyte interface redistribute over time, so that boundary conditions transition from equipotential surfaces at the beginning of the pulse to uniform current density in steady state. Experimental measurements confirmed that, in steady state, the boundary condition corresponds to a uniform current density on electrode surfaces. Arrays with local return electrodes exhibit improved field confinement and can elicit stronger network-mediated retinal response compared to those with a common remote return. Connecting local return electrodes enhances the field penetration depth and allows reducing the return electrode area. Sequential activation of the pixels in large monopolar arrays reduces electrical cross-talk and improves the contrast in pattern stimulation. SIGNIFICANCE Accurate modeling of multielectrode arrays helps optimize the electrode configuration to maximize the spatial resolution, contrast and dynamic range of retinal prostheses.
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Affiliation(s)
- Thomas Flores
- Department of Applied Physics, Stanford University, Stanford, CA 94305, USA
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49
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Suheimat M, Zhu HF, Lambert A, Atchison DA. Relationship between retinal distance and object field angles for finite schematic eyes. Ophthalmic Physiol Opt 2016; 36:404-10. [DOI: 10.1111/opo.12284] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Accepted: 01/17/2016] [Indexed: 11/28/2022]
Affiliation(s)
- Marwan Suheimat
- Institute of Health & Biomedical Innovation and School of Optometry & Vision Sciences; Queensland University of Technology; Brisbane Australia
| | - Hai-Feng Zhu
- College of Science; China University of Petroleum; Qingdao Shandong Province China
| | - Andrew Lambert
- School of Engineering & Information; University of New South Wales Canberra at Australian Defence Force Academy; Canberra Australia
| | - David A. Atchison
- Institute of Health & Biomedical Innovation and School of Optometry & Vision Sciences; Queensland University of Technology; Brisbane Australia
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50
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Wong YT, Halupka K, Kameneva T, Cloherty SL, Grayden DB, Burkitt AN, Meffin H, Shivdasani MN. Spectral distribution of local field potential responses to electrical stimulation of the retina. J Neural Eng 2016; 13:036003. [DOI: 10.1088/1741-2560/13/3/036003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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