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Muralidharan M, Guo T, Tsai D, Lee JI, Fried S, Dokos S, Morley JW, Lovell NH, Shivdasani MN. Neural activity of retinal ganglion cells under continuous, dynamically-modulated high frequency electrical stimulation. J Neural Eng 2024; 21:015001. [PMID: 38290151 DOI: 10.1088/1741-2552/ad2404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Accepted: 01/30/2024] [Indexed: 02/01/2024]
Abstract
Objective.Current retinal prosthetics are limited in their ability to precisely control firing patterns of functionally distinct retinal ganglion cell (RGC) types. The aim of this study was to characterise RGC responses to continuous, kilohertz-frequency-varying stimulation to assess its utility in controlling RGC activity.Approach.We usedin vitropatch-clamp experiments to assess electrically-evoked ON and OFF RGC responses to frequency-varying pulse train sequences. In each sequence, the stimulation amplitude was kept constant while the stimulation frequency (0.5-10 kHz) was changed every 40 ms, in either a linearly increasing, linearly decreasing or randomised manner. The stimulation amplitude across sequences was increased from 10 to 300µA.Main results.We found that continuous stimulation without rest periods caused complex and irreproducible stimulus-response relationships, primarily due to strong stimulus-induced response adaptation and influence of the preceding stimulus frequency on the response to a subsequent stimulus. In addition, ON and OFF populations showed different sensitivities to continuous, frequency-varying pulse trains, with OFF cells generally exhibiting more dependency on frequency changes within a sequence. Finally, the ability to maintain spiking behaviour to continuous stimulation in RGCs significantly reduced over longer stimulation durations irrespective of the frequency order.Significance.This study represents an important step in advancing and understanding the utility of continuous frequency modulation in controlling functionally distinct RGCs. Our results indicate that continuous, kHz-frequency-varying stimulation sequences provide very limited control of RGC firing patterns due to inter-dependency between adjacent frequencies and generally, different RGC types do not display different frequency preferences under such stimulation conditions. For future stimulation strategies using kHz frequencies, careful consideration must be given to design appropriate pauses in stimulation, stimulation frequency order and the length of continuous stimulation duration.
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Affiliation(s)
| | - Tianruo Guo
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW 2052, Australia
| | - David Tsai
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW 2052, Australia
- School of Electrical Engineering & Telecommunications, UNSW, Sydney, NSW 2052, Australia
| | - Jae-Ik Lee
- Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States of America
| | - Shelley Fried
- Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States of America
| | - Socrates Dokos
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW 2052, Australia
| | - John W Morley
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW 2052, Australia
- School of Medicine, Western Sydney University, Penrith, NSW 2751, Australia
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW 2052, Australia
- Tyree Institute of Health Engineering (iHealthE), UNSW, Sydney, NSW 2052, Australia
| | - Mohit N Shivdasani
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW 2052, Australia
- Tyree Institute of Health Engineering (iHealthE), UNSW, Sydney, NSW 2052, Australia
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Ahn J, Yoo Y, Goo YS. Multiple consecutive-biphasic pulse stimulation improves spatially localized firing of retinal ganglion cells in the degenerate retina. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2023; 27:541-553. [PMID: 37884286 PMCID: PMC10613570 DOI: 10.4196/kjpp.2023.27.6.541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 08/08/2023] [Accepted: 08/22/2023] [Indexed: 10/28/2023]
Abstract
Retinal prostheses have shown some clinical success in restoring vision in patients with retinitis pigmentosa. However, the post-implantation visual acuity does not exceed that of legal blindness. The reason for the poor visual acuity might be that (1) degenerate retinal ganglion cells (RGCs) are less responsive to electrical stimulation than normal RGCs, and (2) electrically-evoked RGC spikes show a more widespread not focal response. The single-biphasic pulse electrical stimulation, commonly used in artificial vision, has limitations in addressing these issues. In this study, we propose the benefit of multiple consecutive-biphasic pulse stimulation. We used C57BL/6J mice and C3H/HeJ (rd1) mice for the normal retina and retinal degeneration model. An 8 × 8 multi-electrode array was used to record electrically-evoked RGC spikes. We compared RGC responses when increasing the amplitude of a single biphasic pulse versus increasing the number of consecutive biphasic pulses at the same stimulus charge. Increasing the amplitude of a single biphasic pulse induced more RGC spike firing while the spatial resolution of RGC populations decreased. For multiple consecutive-biphasic pulse stimulation, RGC firing increased as the number of pulses increased, and the spatial resolution of RGC populations was well preserved even up to 5 pulses. Multiple consecutive-biphasic pulse stimulation using two or three pulses in degenerate retinas induced as much RGC spike firing as in normal retinas. These findings suggest that the newly proposed multiple consecutive-biphasic pulse stimulation can improve the visual acuity in prosthesis-implanted patients.
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Affiliation(s)
- Jungryul Ahn
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju 28644, Korea
| | - Yongseok Yoo
- School of Computer Science and Engineering, Soongsil University, Seoul 06978, Korea
| | - Yong Sook Goo
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju 28644, Korea
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Madugula SS, Vilkhu R, Shah NP, Grosberg LE, Kling A, Gogliettino AR, Nguyen H, Hottowy P, Sher A, Litke AM, Chichilnisky EJ. Inference of Electrical Stimulation Sensitivity from Recorded Activity of Primate Retinal Ganglion Cells. J Neurosci 2023; 43:4808-4820. [PMID: 37268418 PMCID: PMC10312054 DOI: 10.1523/jneurosci.1023-22.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 05/22/2023] [Accepted: 05/24/2023] [Indexed: 06/04/2023] Open
Abstract
High-fidelity electronic implants can in principle restore the function of neural circuits by precisely activating neurons via extracellular stimulation. However, direct characterization of the individual electrical sensitivity of a large population of target neurons, to precisely control their activity, can be difficult or impossible. A potential solution is to leverage biophysical principles to infer sensitivity to electrical stimulation from features of spontaneous electrical activity, which can be recorded relatively easily. Here, this approach is developed and its potential value for vision restoration is tested quantitatively using large-scale multielectrode stimulation and recording from retinal ganglion cells (RGCs) of male and female macaque monkeys ex vivo Electrodes recording larger spikes from a given cell exhibited lower stimulation thresholds across cell types, retinas, and eccentricities, with systematic and distinct trends for somas and axons. Thresholds for somatic stimulation increased with distance from the axon initial segment. The dependence of spike probability on injected current was inversely related to threshold, and was substantially steeper for axonal than somatic compartments, which could be identified by their recorded electrical signatures. Dendritic stimulation was largely ineffective for eliciting spikes. These trends were quantitatively reproduced with biophysical simulations. Results from human RGCs were broadly similar. The inference of stimulation sensitivity from recorded electrical features was tested in a data-driven simulation of visual reconstruction, revealing that the approach could significantly improve the function of future high-fidelity retinal implants.SIGNIFICANCE STATEMENT This study demonstrates that individual in situ primate retinal ganglion cells of different types respond to artificially generated, external electrical fields in a systematic manner, in accordance with theoretical predictions, that allows for prediction of electrical stimulus sensitivity from recorded spontaneous activity. It also provides evidence that such an approach could be immensely helpful in the calibration of clinical retinal implants.
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Affiliation(s)
- Sasidhar S Madugula
- Neurosciences PhD Program, Stanford University, Stanford, California 94305
- School of Medicine, Stanford University, Stanford, California 94305
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305
| | - Ramandeep Vilkhu
- Department of Electrical Engineering, Stanford University, Stanford, California 94305
| | - Nishal P Shah
- Department of Neurosurgery, Stanford University, Stanford, California 94305
- Department of Electrical Engineering, Stanford University, Stanford, California 94305
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305
| | - Lauren E Grosberg
- Department of Neurosurgery, Stanford University, Stanford, California 94305
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305
- Facebook Reality Labs, Facebook, Mountain View, California 94040
| | - Alexandra Kling
- Department of Neurosurgery, Stanford University, Stanford, California 94305
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305
| | - Alex R Gogliettino
- Neurosciences PhD Program, Stanford University, Stanford, California 94305
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305
| | - Huy Nguyen
- Department of Neurosurgery, Stanford University, Stanford, California 94305
| | - Paweł Hottowy
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Krakow, Poland 30-059
| | - Alexander Sher
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, California 95064
| | - Alan M Litke
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, California 95064
| | - E J Chichilnisky
- Department of Neurosurgery, Stanford University, Stanford, California 94305
- Department of Ophthalmology, Stanford University, Stanford, California 94305
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305
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Xu A, Beyeler M. Retinal ganglion cells undergo cell type-specific functional changes in a computational model of cone-mediated retinal degeneration. Front Neurosci 2023; 17:1147729. [PMID: 37274203 PMCID: PMC10233015 DOI: 10.3389/fnins.2023.1147729] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Accepted: 05/02/2023] [Indexed: 06/06/2023] Open
Abstract
Introduction Understanding the retina in health and disease is a key issue for neuroscience and neuroengineering applications such as retinal prostheses. During degeneration, the retinal network undergoes complex and multi-stage neuroanatomical alterations, which drastically impact the retinal ganglion cell (RGC) response and are of clinical importance. Here we present a biophysically detailed in silico model of the cone pathway in the retina that simulates the network-level response to both light and electrical stimulation. Methods The model included 11, 138 cells belonging to nine different cell types (cone photoreceptors, horizontal cells, ON/OFF bipolar cells, ON/OFF amacrine cells, and ON/OFF ganglion cells) confined to a 300 × 300 × 210μm patch of the parafoveal retina. After verifying that the model reproduced seminal findings about the light response of retinal ganglion cells (RGCs), we systematically introduced anatomical and neurophysiological changes (e.g., reduced light sensitivity of photoreceptor, cell death, cell migration) to the network and studied their effect on network activity. Results The model was not only able to reproduce common findings about RGC activity in the degenerated retina, such as hyperactivity and increased electrical thresholds, but also offers testable predictions about the underlying neuroanatomical mechanisms. Discussion Overall, our findings demonstrate how biophysical changes typified by cone-mediated retinal degeneration may impact retinal responses to light and electrical stimulation. These insights may further our understanding of retinal processing and inform the design of retinal prostheses.
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Affiliation(s)
- Aiwen Xu
- Department of Computer Science, University of California, California, Santa Barbara, CA, United States
| | - Michael Beyeler
- Department of Computer Science, University of California, California, Santa Barbara, CA, United States
- Department of Psychological & Brain Sciences, University of California, California, Santa Barbara, CA, United States
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Xu A, Beyeler M. Retinal ganglion cells undergo cell typeâ€"specific functional changes in a biophysically detailed model of retinal degeneration. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.13.523982. [PMID: 36711897 PMCID: PMC9882163 DOI: 10.1101/2023.01.13.523982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Understanding the retina in health and disease is a key issue for neuroscience and neuroengineering applications such as retinal prostheses. During degeneration, the retinal network undergoes complex and multi-stage neuroanatomical alterations, which drastically impact the retinal ganglion cell (RGC) response and are of clinical importance. Here we present a biophysically detailed in silico model of retinal degeneration that simulates the network-level response to both light and electrical stimulation as a function of disease progression. The model is not only able to reproduce common findings about RGC activity in the degenerated retina, such as hyperactivity and increased electrical thresholds, but also offers testable predictions about the underlying neuroanatomical mechanisms. Overall, our findings demonstrate how biophysical changes associated with retinal degeneration affect retinal responses to both light and electrical stimulation, which may further our understanding of visual processing in the retina as well as inform the design and application of retinal prostheses.
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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: 6] [Impact Index Per Article: 3.0] [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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Yunzab M, Soto-Breceda A, Maturana M, Kirkby S, Slattery M, Newgreen A, Meffin H, Kameneva T, Burkitt AN, Ibbotson M, Tong W. Preferential modulation of individual retinal ganglion cells by electrical stimulation. J Neural Eng 2022; 19. [PMID: 35917811 DOI: 10.1088/1741-2552/ac861f] [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: 01/05/2022] [Accepted: 08/01/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Retinal prostheses have been able to recover partial vision in blind patients with retinal degeneration by electrically stimulating surviving cells in the retina, such as retinal ganglion cells (RGCs), but the restored vision is limited. This is partly due to non-preferential stimulation of all RGCs near a single stimulating electrode, which include cells that conflict in their response properties and their contribution to the vision process. Our study proposes a stimulation strategy to preferentially stimulate individual RGCs based on their temporal electrical receptive fields (tERFs). APPROACH We recorded the responses of RGCs using whole-cell current-clamp and demonstrated the stimulation strategy, first using intracellular stimulation, then via extracellular stimulation. MAIN RESULTS We successfully reconstructed the tERFs according to the RGC response to Gaussian white noise current stimulation. The characteristics of the tERFs were extracted and compared according to the morphological and light response types of the cells. By re-delivering stimulation trains that are composed of the tERFs obtained from different cells, we could target individual RGCs as the cells showed lower activation thresholds to their own tERFs. SIGNIFICANCE This proposed stimulation strategy implemented in the next generation of recording and stimulating retinal prostheses may improve the quality of artificial vision.
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Affiliation(s)
- Molis Yunzab
- National Vision Research Institute, Australian College of Optometry, Corner of Keppel and Cardigan Streets, Carlton, Victoria, 3053, AUSTRALIA
| | - Artemio Soto-Breceda
- National Vision Research Institute, Australian College of Optometry, Corner of Keppel and Cardigan Streets, Carlton, Victoria, 3053, AUSTRALIA
| | - Matias Maturana
- National Vision Research Institute, Australian College of Optometry, Corner of Keppel and Cardigan Streets, Carlton, Victoria, 3053, AUSTRALIA
| | - Stephanie Kirkby
- National Vision Research Institute, Australian College of Optometry, Corner of Keppel and Cardigan Streets, Carlton, Victoria, 3053, AUSTRALIA
| | - Maximilian Slattery
- National Vision Research Institute, Australian College of Optometry, Corner of Keppel and Cardigan Streets, Carlton, Victoria, 3053, AUSTRALIA
| | - Anton Newgreen
- National Vision Research Institute, Australian College of Optometry, Corner of Keppel and Cardigan Streets, Carlton, Victoria, 3053, AUSTRALIA
| | - Hamish Meffin
- Biomedical Engineering, The University of Melbourne, Grattan Street, Melbourne, Victoria, 3010, AUSTRALIA
| | - Tatiana Kameneva
- School of Science, Engineering, and Computing Technologies, Swinburne University of Technology, School of Science, Engineering, and Computing Technologies, Swinburne University of Technology, Hawthorn, Victoria, 3122, AUSTRALIA
| | - Anthony N Burkitt
- Department of Biomedical Engineering, University of Melbourne, University of Melbourne, Parkville, Victoria, 3010, AUSTRALIA
| | - Michael Ibbotson
- National Vision Research Institute, Australian College of Optometry, Corner of Keppel and Cardigan Streets, Carlton, Victoria, 3053, AUSTRALIA
| | - Wei Tong
- University of Melbourne, School of Physics, University of Melbourne, Parkville, Melbourne, Victoria, 3010, AUSTRALIA
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8
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Ingensiep C, Schaffrath K, Walter P, Johnen S. Effects of Hydrostatic Pressure on Electrical Retinal Activity in a Multielectrode Array-Based ex vivo Glaucoma Acute Model. Front Neurosci 2022; 16:831392. [PMID: 35177963 PMCID: PMC8845467 DOI: 10.3389/fnins.2022.831392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 01/04/2022] [Indexed: 11/13/2022] Open
Abstract
Glaucoma is a heterogeneous eye disease causing atrophy of the optic nerve head (ONH). The optic nerve is formed by the axons of the retinal ganglion cells (RGCs) that transmit visual input to the brain. The progressive RGC loss during glaucoma leads to irreversible vision loss. An elevated intraocular pressure (IOP) is described as main risk factor in glaucoma. In this study, a multielectrode array (MEA)-based ex vivo glaucoma acute model was established and the effects of hydrostatic pressure (10, 30, 60, and 90 mmHg) on the functionality and survival of adult male and female wild-type mouse (C57BL/6) retinae were investigated. Spontaneous activity, response rate to electrical and light stimulation, and bursting behavior of RGCs was analyzed prior, during, and after pressure stress. No pressure related effects on spontaneous firing and on the response rate of the RGCs were observed. Even a high pressure level (90 mmHg for 2 h) did not disturb the RGC functionality. However, the cells’ bursting behavior significantly changed under 90 mmHg. The number of spikes in bursts doubled during pressure application and stayed on a high level after pressure stress. Addition of the amino sulfonic acid taurine (1 mM) showed a counteracting effect. OFF ganglion cells did not reveal an increase in bursts under pressure stress. Live/dead staining after pressure application showed no significant changes in RGC survival. The findings of our ex vivo model suggest that RGCs are tolerant toward high, short-time pressure stress.
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Hadjinicolaou AE, Meffin H, Maturana MI, Cloherty SL, Ibbotson MR. Prosthetic vision: devices, patient outcomes and retinal research. Clin Exp Optom 2021; 98:395-410. [DOI: 10.1111/cxo.12342] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 07/06/2015] [Accepted: 08/04/2015] [Indexed: 12/11/2022] Open
Affiliation(s)
- Alex E Hadjinicolaou
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia,
- ARC Centre of Excellence for Integrative Brain Function and Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia,
| | - Hamish Meffin
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia,
- ARC Centre of Excellence for Integrative Brain Function and Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia,
| | - Matias I Maturana
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia,
- Department of Electrical and Electronic Engineering, The University of Melbourne, Parkville, Victoria, Australia,
| | - Shaun L Cloherty
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia,
- ARC Centre of Excellence for Integrative Brain Function and Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia,
- Department of Electrical and Electronic Engineering, The University of Melbourne, Parkville, Victoria, Australia,
| | - Michael R Ibbotson
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia,
- ARC Centre of Excellence for Integrative Brain Function and Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia,
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Chenais NAL, Airaghi Leccardi MJI, Ghezzi D. Naturalistic spatiotemporal modulation of epiretinal stimulation increases the response persistence of retinal ganglion cell. J Neural Eng 2021; 18. [DOI: 10.1088/1741-2552/abcd6f] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 11/24/2020] [Indexed: 12/24/2022]
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Oesterle J, Behrens C, Schröder C, Hermann T, Euler T, Franke K, Smith RG, Zeck G, Berens P. Bayesian inference for biophysical neuron models enables stimulus optimization for retinal neuroprosthetics. eLife 2020; 9:e54997. [PMID: 33107821 PMCID: PMC7673784 DOI: 10.7554/elife.54997] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 10/26/2020] [Indexed: 01/02/2023] Open
Abstract
While multicompartment models have long been used to study the biophysics of neurons, it is still challenging to infer the parameters of such models from data including uncertainty estimates. Here, we performed Bayesian inference for the parameters of detailed neuron models of a photoreceptor and an OFF- and an ON-cone bipolar cell from the mouse retina based on two-photon imaging data. We obtained multivariate posterior distributions specifying plausible parameter ranges consistent with the data and allowing to identify parameters poorly constrained by the data. To demonstrate the potential of such mechanistic data-driven neuron models, we created a simulation environment for external electrical stimulation of the retina and optimized stimulus waveforms to target OFF- and ON-cone bipolar cells, a current major problem of retinal neuroprosthetics.
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Affiliation(s)
- Jonathan Oesterle
- Institute for Ophthalmic Research, University of TübingenTübingenGermany
| | - Christian Behrens
- Institute for Ophthalmic Research, University of TübingenTübingenGermany
| | - Cornelius Schröder
- Institute for Ophthalmic Research, University of TübingenTübingenGermany
| | - Thoralf Hermann
- Naturwissenschaftliches und Medizinisches Institut an der Universität TübingenReutlingenGermany
| | - Thomas Euler
- Institute for Ophthalmic Research, University of TübingenTübingenGermany
- Center for Integrative Neuroscience, University of TübingenTübingenGermany
- Bernstein Center for Computational Neuroscience, University of TübingenTübingenGermany
| | - Katrin Franke
- Institute for Ophthalmic Research, University of TübingenTübingenGermany
- Bernstein Center for Computational Neuroscience, University of TübingenTübingenGermany
| | - Robert G Smith
- Department of Neuroscience, University of PennsylvaniaPhiladelphiaUnited States
| | - Günther Zeck
- Naturwissenschaftliches und Medizinisches Institut an der Universität TübingenReutlingenGermany
| | - Philipp Berens
- Institute for Ophthalmic Research, University of TübingenTübingenGermany
- Center for Integrative Neuroscience, University of TübingenTübingenGermany
- Bernstein Center for Computational Neuroscience, University of TübingenTübingenGermany
- Institute for Bioinformatics and Medical Informatics, University of TübingenTübingenGermany
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12
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Retinal Drug Delivery: Rethinking Outcomes for the Efficient Replication of Retinal Behavior. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10124258] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The retina is a highly organized structure that is considered to be "an approachable part of the brain." It is attracting the interest of development scientists, as it provides a model neurovascular system. Over the last few years, we have been witnessing significant development in the knowledge of the mechanisms that induce the shape of the retinal vascular system, as well as knowledge of disease processes that lead to retina degeneration. Knowledge and understanding of how our vision works are crucial to creating a hardware-adaptive computational model that can replicate retinal behavior. The neuronal system is nonlinear and very intricate. It is thus instrumental to have a clear view of the neurophysiological and neuroanatomic processes and to take into account the underlying principles that govern the process of hardware transformation to produce an appropriate model that can be mapped to a physical device. The mechanistic and integrated computational models have enormous potential toward helping to understand disease mechanisms and to explain the associations identified in large model-free data sets. The approach used is modulated and based on different models of drug administration, including the geometry of the eye. This work aimed to review the recently used mathematical models to map a directed retinal network.
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Ha Y, Yoo HJ, Shin S, Jun SB. Hemispherical Microelectrode Array for Ex Vivo Retinal Neural Recording. MICROMACHINES 2020; 11:mi11050538. [PMID: 32466300 PMCID: PMC7281771 DOI: 10.3390/mi11050538] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 05/21/2020] [Accepted: 05/22/2020] [Indexed: 12/13/2022]
Abstract
To investigate the neuronal visual encoding process in the retina, researchers have performed in vitro and ex vivo electrophysiological experiments using animal retinal tissues. The microelectrode array (MEA) has become a key component in retinal experiments because it enables simultaneous neural recording from a population of retinal neurons. However, in most retinal experiments, it is inevitable that the retinal tissue is flattened on the planar MEA, becoming deformed from the original hemispherical shape. During the tissue deforming process, the retina is subjected to mechanical stress, which can induce abnormal physiological conditions. To overcome this problem, in this study, we propose a hemispherical MEA with a curvature that allows retinal tissues to adhere closely to electrodes without tissue deformation. The electrode array is fabricated by stretching a thin, flexible polydimethylsiloxane (PDMS) electrode layer onto a hemispherical substrate. To form micro patterns of electrodes, laser processing is employed instead of conventional thin-film microfabrication processes. The feasibility for neural recording from retinal tissues using this array is shown by conducting ex vivo retinal experiments. We anticipate that the proposed techniques for hemispherical MEAs can be utilized not only for ex vivo retinal studies but also for various flexible electronics.
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Affiliation(s)
- Yoonhee Ha
- Department of Electronic and Electrical Engineering, Ewha Womans University, Seoul 03760, Korea; (Y.H.); (H.-J.Y.)
| | - Hyun-Ji Yoo
- Department of Electronic and Electrical Engineering, Ewha Womans University, Seoul 03760, Korea; (Y.H.); (H.-J.Y.)
| | - Soowon Shin
- Department of Bioengineering, TODOC Co., Ltd., Seoul 08394, Korea;
| | - Sang Beom Jun
- Department of Electronic and Electrical Engineering, Ewha Womans University, Seoul 03760, Korea; (Y.H.); (H.-J.Y.)
- Department of Brain and Cognitive Sciences, Ewha Womans University, Seoul 03760, Korea
- Correspondence: ; Tel.: +82-2-3277-3892
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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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15
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Shalbaf F, Lovell NH, Dokos S, Trew M, Vaghefi E. Foveal eccentricity can influence activation threshold in subretinal electrical stimulation. Biomed Phys Eng Express 2019. [DOI: 10.1088/2057-1976/ab0b85] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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16
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Alqahtani A, Abed AA, Anderson EE, Lovell NH, Dokos S. A Multi-Domain Continuum Model of Electrical Stimulation of Healthy and Degenerate Retina. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2018; 2018:6117-6120. [PMID: 30441730 DOI: 10.1109/embc.2018.8513665] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A continuum multi-domain model of electrical stimulation of the retina is presented and validated against retinal ganglion cell (RGC) excitation thresholds reported in a recently published in vitro experimental study. We applied our model to investigate the response of the RGC layer to electrical stimulation during mid-to-late stage retinal degeneration for both epiretinal and suprachoroidal configurations. Interestingly, our model predicted that suprachoroidal stimulation of the degenerate retina required increased current thresholds, mainly because of the presence of the glial scar layer. In contrast, epiretinal stimulation thresholds were almost similar for both healthy and degenerate models. The latter finding implies that there is no influence of the glial scar layer on epiretinal stimulation current thresholds.
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17
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Nimmagadda K, Weiland JD. Retinotopic Responses in the Visual Cortex Elicited by Epiretinal Electrical Stimulation in Normal and Retinal Degenerate Rats. Transl Vis Sci Technol 2018; 7:33. [PMID: 30402340 PMCID: PMC6213779 DOI: 10.1167/tvst.7.5.33] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 08/24/2018] [Indexed: 01/31/2023] Open
Abstract
Purpose Electronic retinal prostheses restore vision in people with outer retinal degeneration by electrically stimulating the inner retina. We characterized visual cortex electrophysiologic response elicited by electrical stimulation of retina in normally sighted and retinal degenerate rats. Methods Nine normally sighted Long Evans and 11 S334ter line 3 retinal degenerate (rd) rats were used to map cortical responses elicited by epiretinal electrical stimulation in four quadrants of the retina. Six normal and six rd rats were used to compare the dendritic spine density of neurons in the visual cortex. Results The rd rats required higher stimulus amplitudes to elicit responses in the visual cortex. The cortical electrically evoked responses (EERs) for both healthy and rd rats show a dose-response characteristic with respect to the stimulus amplitude. The EER maps in healthy rats show retinotopic organization. For rd rats, cortical retinotopy is not well preserved. The neurons in the visual cortex of rd rats show a 10% higher dendritic spine density than in the healthy rats. Conclusions Cortical activity maps, produced when epiretinal stimulation is applied to quadrants of the retina, exhibit retinotopy in normal but not rd rats. This is likely due to a combination of degeneration of the retina and increased stimulus thresholds in rd, which broadens the activated area of the retina. Translational Relevance Loss of retinotopy is evident in rd rats. If a similar loss of retinotopy is present in humans, retinal prostheses design must include flexibility to account for patient specific variability.
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Affiliation(s)
- Kiran Nimmagadda
- Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, USA.,USC - Caltech MD/PhD Program, Los Angeles, CA, USA
| | - James D Weiland
- Department of Biomedical Engineering, The University of Michigan, Ann Arbor, MI, USA.,Department of Ophthalmology and Visual Sciences, The University of Michigan, Ann Arbor, MI, USA
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18
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Corna A, Herrmann T, Zeck G. Electrode-size dependent thresholds in subretinal neuroprosthetic stimulation. J Neural Eng 2018; 15:045003. [DOI: 10.1088/1741-2552/aac1c8] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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19
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Ren YM, Weng CH, Zhao CJ, Yin ZQ. Changes in intrinsic excitability of ganglion cells in degenerated retinas of RCS rats. Int J Ophthalmol 2018; 11:756-765. [PMID: 29862172 DOI: 10.18240/ijo.2018.05.07] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2018] [Accepted: 03/16/2018] [Indexed: 11/23/2022] Open
Abstract
AIM To evaluate the intrinsic excitability of retinal ganglion cells (RGCs) in degenerated retinas. METHODS The intrinsic excitability of various morphologically defined RGC types using a combination of patch-clamp recording and the Lucifer yellow tracer in retinal whole-mount preparations harvested from Royal College of Surgeons (RCS) rats, a common retinitis pigmentosa (RP) model, in a relatively late stage of retinal degeneration (P90) were investigated. Several parameters of RGC morphologies and action potentials (APs) were measured and compared to those of non-dystrophic control rats, including dendritic stratification, dendritic field diameter, peak amplitude, half width, resting membrane potential, AP threshold, depolarization to threshold, and firing rates. RESULTS Compared with non-dystrophic control RGCs, more depolarizations were required to reach the AP threshold in RCS RGCs with low spontaneous spike rates and in RCS OFF cells (especially A2o cells), and RCS RGCs maintained their dendritic morphologies, resting membrane potentials and capabilities to generate APs. CONCLUSION RGCs are relatively well preserved morphologically and functionally, and some cells are more susceptible to decreased excitability during retinal degeneration. These findings provide valuable considerations for optimizing RP therapeutic strategies.
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Affiliation(s)
- Yi-Ming Ren
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University); Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing 400038, China
| | - Chuan-Huang Weng
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University); Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing 400038, China
| | - Cong-Jian Zhao
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University); Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing 400038, China
| | - Zheng-Qin Yin
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University); Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing 400038, China
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20
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Loizos K, Marc R, Humayun M, Anderson JR, Jones BW, Lazzi G. Increasing Electrical Stimulation Efficacy in Degenerated Retina: Stimulus Waveform Design in a Multiscale Computational Model. IEEE Trans Neural Syst Rehabil Eng 2018; 26:1111-1120. [PMID: 29877835 PMCID: PMC6005361 DOI: 10.1109/tnsre.2018.2832055] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A computational model of electrical stimulation of the retina is proposed for investigating current waveforms used in prosthetic devices for restoring partial vision lost to retinal degenerative diseases. The model framework combines a connectome-based neural network model characterized by accurate morphological and synaptic properties with an admittance method model of bulk tissue and prosthetic electronics. In this model, the retina was computationally "degenerated," considering cellular death and anatomical changes that occur early in disease, as well as altered neural behavior that develops throughout the neurodegeneration and is likely interfering with current attempts at restoring vision. A resulting analysis of stimulation range and threshold of ON ganglion cells within the retina that are either healthy or in beginning stages of degeneration is presented for currently used stimulation waveforms, and an asymmetric biphasic current stimulation for subduing spontaneous firing to allow increased control over ganglion cell firing patterns in degenerated retina is proposed. Results show that stimulation thresholds of retinal ganglion cells do not notably vary after beginning stages of retina degeneration. In addition, simulation of proposed asymmetric waveforms showed the ability to enhance the control of ganglion cell firing via electrical stimulation.
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21
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Celik ME, Karagoz I. Comparison of Monophasic and Biphasic Electrical Stimulation by Using Temporal Analysis for Different Inter-electrode Spacings in the Hexagonal Arrays. ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 2018. [DOI: 10.1007/s13369-017-2918-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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22
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Watterson WJ, Montgomery RD, Taylor RP. Modeling the Improved Visual Acuity Using Photodiode Based Retinal Implants Featuring Fractal Electrodes. Front Neurosci 2018; 12:277. [PMID: 29740278 PMCID: PMC5928399 DOI: 10.3389/fnins.2018.00277] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 04/10/2018] [Indexed: 11/23/2022] Open
Abstract
Electronically restoring vision to patients blinded by severe retinal degenerations is rapidly becoming a realizable feat through retinal implants. Upon receiving an implant, previously blind patients can now detect light, locate objects, and determine object motion direction. However, the restored visual acuity (VA) is still significantly below the legal blindness level (VA < 20/200). The goal of this research is to optimize the inner electrode geometry in photovoltaic subretinal implants in order to restore vision to a VA better than blindness level. We simulated neural stimulation by 20 μm subretinal photovoltaic implants featuring square or fractal inner electrodes by: (1) calculating the voltage generated on the inner electrode based on the amount of light entering the photodiode, (2) mapping how this voltage spreads throughout the extracellular space surrounding retinal bipolar neurons, and (3) determining if these extracellular voltages are sufficient for neural stimulation. By optimizing the fractal inner electrode geometry, we show that all neighboring neurons can be stimulated using an irradiance of 12 mW/mm2, while the optimized square only stimulates ~10% of these neurons at an equivalent irradiance. The 20 μm fractal electrode can thus theoretically restore VA up to 20/80, if other limiting factors common to retinal degenerations, such as glia scarring and rewiring of retinal circuits, could be reduced. For the optimized square to stimulate all neighboring neurons, the irradiance has to be increased by almost 300%, which is very near the maximum permissible exposure safety limit. This demonstration that fractal electrodes can stimulate targeted neurons for long periods using safe irradiance levels highlights the possibility for restoring vision to a VA better than the blindness level using photodiode-based retinal implants.
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Affiliation(s)
| | | | - Richard P Taylor
- Physics Department, University of Oregon, Eugene, OR, United States
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23
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Walston ST, Chow RH, Weiland JD. Direct measurement of bipolar cell responses to electrical stimulation in wholemount mouse retina. J Neural Eng 2018. [PMID: 29513646 DOI: 10.1088/1741-2552/aab4ed] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVE This in vitro investigation examines the response of retinal bipolar cells to extracellular electrical stimulation. APPROACH In vitro investigations characterizing the response of retinal neurons to electrical stimulation have primarily focused on retinal ganglion cells because they are the output neurons of the retina and their superficial position in the retina makes them readily accessible to in vitro recording techniques. Thus, the majority of information regarding the response of inner retinal neurons has been inferred from ganglion cell activity. Here we use patch clamp electrophysiology to directly record electrically-evoked activity in bipolar cells within the inner retina of normal Tg(Gng13-EGFP)GI206Gsat and degenerate rd10 Tg(Gng13-EGFP)GI206Gsat mice using a wholemount preparation. MAIN RESULTS Bipolar cells respond to electrical stimulation with time-locked depolarizing voltage transients. The latency of the response declines with increases in stimulation amplitude. A desensitizing response is observed during repeated stimulation with 25 ms biphasic current pulses delivered at pulse rates greater than 6 pps. A burst of long-latency (200-1000 ms) inhibitory postsynaptic potentials are evoked by the stimulus and the burst exhibits evidence of a lower and upper stimulation threshold. SIGNIFICANCE These results provide insights into the various types of bipolar cell activity elicited by electrical stimulation and may be useful for future retinal prosthesis stimulation protocols. This investigation uses patch clamp electrophysiology to provide direct analysis of ON-type bipolar cell responses to electrical stimulation in a wholemount retina preparation. It explores the effects of variable stimulus amplitudes, pulse widths, and frequencies in both normal and degenerate retina. The analysis adds to a body of work largely based upon indirect measurements of bipolar cell activity, and the methodology demonstrates an alternative retina preparation technique in which to acquire single-cell activity.
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Affiliation(s)
- Steven T Walston
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90007, United States of America
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24
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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: 40] [Impact Index Per Article: 6.7] [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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25
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Haselier C, Biswas S, Rösch S, Thumann G, Müller F, Walter P. Correlations between specific patterns of spontaneous activity and stimulation efficiency in degenerated retina. PLoS One 2017; 12:e0190048. [PMID: 29281713 PMCID: PMC5744965 DOI: 10.1371/journal.pone.0190048] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 12/07/2017] [Indexed: 11/20/2022] Open
Abstract
Retinal prostheses that are currently used to restore vision in patients suffering from retinal degeneration are not adjusted to the changes occurring during the remodeling process of the retina. Recent studies revealed abnormal rhythmic activity in the retina of genetic mouse models of retinitis pigmentosa. Here we describe this abnormal activity also in a pharmacologically-induced (MNU) mouse model of retinal degeneration. To investigate how this abnormal activity affects the excitability of retinal ganglion cells, we recorded the electrical activity from whole mounted retinas of rd10 mice and MNU-treated mice using a microelectrode array system and applied biphasic current pulses of different amplitude and duration to stimulate ganglion cells electrically. We show that the electrical stimulation efficiency is strongly reduced in degenerated retinas, in particular when abnormal activity such as oscillations and rhythmic firing of bursts of action potentials can be observed. Using a prestimulus pulse sequence, we could abolish rhythmic retinal activity. Under these conditions, the stimulation efficiency was enhanced in a few cases but not in the majority of tested cells. Nevertheless, this approach supports the idea that modified stimulation protocols could help to improve the efficiency of retinal prostheses in the future.
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Affiliation(s)
| | - Sonia Biswas
- Institute of Complex Systems, Cellular Biophysics, ICS-4, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Sarah Rösch
- Department of Ophthalmology, RWTH Aachen University, Aachen, Germany
| | - Gabriele Thumann
- Department of Ophthalmology, RWTH Aachen University, Aachen, Germany
| | - Frank Müller
- Institute of Complex Systems, Cellular Biophysics, ICS-4, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Peter Walter
- Department of Ophthalmology, RWTH Aachen University, Aachen, Germany
- * E-mail:
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26
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Ryu SB, Choi JW, Ahn KN, Goo YS, Kim KH. Amplitude Modulation-based Electrical Stimulation for Encoding Multipixel Spatiotemporal Visual Information in Retinal Neural Activities. J Korean Med Sci 2017; 32:900-907. [PMID: 28480646 PMCID: PMC5426244 DOI: 10.3346/jkms.2017.32.6.900] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 03/29/2017] [Indexed: 12/17/2022] Open
Abstract
Retinal implants have been developed as a promising way to restore partial vision for the blind. The observation and analysis of neural activities can offer valuable insights for successful prosthetic electrical stimulation. Retinal ganglion cell (RGC) activities have been investigated to provide knowledge on the requirements for electrical stimulation, such as threshold current and the effect of stimulation waveforms. To develop a detailed 'stimulation strategy' for faithful delivery of spatiotemporal visual information to the brain, it is essential to examine both the temporal and spatial characteristics of RGC responses, whereas previous studies were mainly focused on one or the other. In this study, we investigate whether the spatiotemporal visual information can be decoded from the RGC network activity evoked by patterned electrical stimulation. Along with a thorough characterization of spatial spreading of stimulation current and temporal information encoding, we demonstrated that multipixel spatiotemporal visual information can be accurately decoded from the population activities of RGCs stimulated by amplitude-modulated pulse trains. We also found that the details of stimulation, such as pulse amplitude range and pulse rate, were crucial for accurate decoding. Overall, the results suggest that useful visual function may be restored by amplitude modulation-based retinal stimulation.
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Affiliation(s)
- Sang Baek Ryu
- Department of Biomedical Engineering, Yonsei University Wonju College of Health Science, Wonju, Korea
| | - Jeong Woo Choi
- Department of Biomedical Engineering, Yonsei University Wonju College of Health Science, Wonju, Korea
| | - Kun No Ahn
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju, Korea
| | - Yong Sook Goo
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju, Korea
| | - Kyung Hwan Kim
- Department of Biomedical Engineering, Yonsei University Wonju College of Health Science, Wonju, Korea.
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27
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Jalligampala A, Sekhar S, Zrenner E, Rathbun DL. Optimal voltage stimulation parameters for network-mediated responses in wild type and rd10 mouse retinal ganglion cells. J Neural Eng 2017; 14:026004. [PMID: 28155848 DOI: 10.1088/1741-2552/14/2/026004] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
To further improve the quality of visual percepts elicited by microelectronic retinal prosthetics, substantial efforts have been made to understand how retinal neurons respond to electrical stimulation. It is generally assumed that a sufficiently strong stimulus will recruit most retinal neurons. However, recent evidence has shown that the responses of some retinal neurons decrease with excessively strong stimuli (a non-monotonic response function). Therefore, it is necessary to identify stimuli that can be used to activate the majority of retinal neurons even when such non-monotonic cells are part of the neuronal population. Taking these non-monotonic responses into consideration, we establish the optimal voltage stimulation parameters (amplitude, duration, and polarity) for epiretinal stimulation of network-mediated (indirect) ganglion cell responses. We recorded responses from 3958 mouse retinal ganglion cells (RGCs) in both healthy (wild type, WT) and a degenerating (rd10) mouse model of retinitis pigmentosa-using flat-mounted retina on a microelectrode array. Rectangular monophasic voltage-controlled pulses were presented with varying voltage, duration, and polarity. We found that in 4-5 weeks old rd10 mice the RGC thresholds were comparable to those of WT. There was a marked response variability among mouse RGCs. To account for this variability, we interpolated the percentage of RGCs activated at each point in the voltage-polarity-duration stimulus space, thus identifying the optimal voltage-controlled pulse (-2.4 V, 0.88 ms). The identified optimal voltage pulse can activate at least 65% of potentially responsive RGCs in both mouse strains. Furthermore, this pulse is well within the range of stimuli demonstrated to be safe and effective for retinal implant patients. Such optimized stimuli and the underlying method used to identify them support a high yield of responsive RGCs and will serve as an effective guideline for future in vitro investigations of retinal electrostimulation by establishing standard stimuli for each unique experimental condition.
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Affiliation(s)
- Archana Jalligampala
- Institute for Ophthalmic Research, Eberhard Karls University, D-72076 Tübingen, Germany. Werner Reichardt Centre for Integrative Neuroscience (CIN), D-72076 Tübingen, Germany. Graduate Training Center of Neuroscience/International Max Planck Research School, D-72074 Tübingen, Germany
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Liu G, Li H, Liu X, Xu D, Wang F. Structural analysis of retinal photoreceptor ellipsoid zone and postreceptor retinal layer associated with visual acuity in patients with retinitis pigmentosa by ganglion cell analysis combined with OCT imaging. Medicine (Baltimore) 2016; 95:e5785. [PMID: 28033301 PMCID: PMC5207597 DOI: 10.1097/md.0000000000005785] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
The aim of this study was to examine changes in photoreceptor ellipsoid zone (EZ) and postreceptor retinal layer in retinitis pigmentosa (RP) patients by ganglion cell analysis (GCA) combined with optical coherence tomography (OCT) imaging to evaluate the structure-function relationships between retinal layer changes and best corrected visual acuity (BCVA). Sixty-eight eyes of 35 patients with RP and 65 eyes of 35 normal controls were analyzed in the study. The average length of EZ was 911.1 ± 208.8 μm in RP patients, which was shortened with the progression of the disease on the OCT images. The average ganglion cell-inner plexiform layer thickness (GCIPLT) was 54.7 ± 18.9 μm in RP patients, while in normal controls it was 85.6 ± 6.8 μm. The GCIPLT in all quarters became significantly thinner along with outer retinal thinning. There was a significantly positive correlation between BCVA and EZ (r = -0.7622, P < 0.001) and GCIPLT (r = -0.452, P < 0.001). Therefore, we assess the retinal layer changes from a new perspective in RP patients, which suggests that EZ and GCIPLT obtained by GCA combined with OCT imaging are the direct and valid indicators to diagnosis and predict the pathological process of RP.
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Park DJ, Senok SS, Goo YS. Degeneration stage-specific response pattern of retinal ganglion cell spikes in rd10 mouse retina. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2016; 2015:3351-4. [PMID: 26737010 DOI: 10.1109/embc.2015.7319110] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
It is known that with retinal degeneration there is rewiring of retinal networks. Consequently, electrical stimulation of the degenerating retina produces responses that differ according to the stage of retinal degeneration. We sought to delineate a degeneration stage-specific parameter for the response pattern of retinal ganglion cell (RGC) spikes as a strategy for stage-specific electrical stimulation for perceptual efficiency of prosthetic vision devices. Electrically-evoked RGC spikes were recorded at different degeneration stages in the rd10 mouse model for human retinitis pigmentosa (RP). Retinal explants mounted on an 8×8 multi-electrode array were stimulated by applying 1 Hz cathodic-phase first biphasic current pulses. RGC firing rate during the first 100 ms post-stimulus was compared to that during the 100-1000 ms period and a response ratio of 100 ms (RR100 ms) was calculated through the different postnatal weeks. Our results show that during post-stimulus 100-1000 ms, the degree of correlation between pulse amplitude and evoked RGC spikes drastically decreases at PNW 4.5. This pattern was closely matched by the RR100 ms curve at this stage. We conclude that the RR100 ms might be a good indicator of the therapeutic potential of a retinal electrical prosthesis.
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Im M, Fried SI. Temporal properties of network-mediated responses to repetitive stimuli are dependent upon retinal ganglion cell type. J Neural Eng 2016; 13:025002. [PMID: 26905231 PMCID: PMC4931047 DOI: 10.1088/1741-2560/13/2/025002] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE To provide artificially-elicited vision that is temporally dynamic, retinal prosthetic devices will need to repeatedly stimulate retinal neurons. However, given the diversity of physiological types of retinal ganglion cells (RGCs) as well as the heterogeneity of their responses to electric stimulation, temporal properties of RGC responses have not been adequately investigated. Here, we explored the cell type dependence of network-mediated RGC responses to repetitive electric stimulation at various stimulation rates. APPROACH We examined responses of ON and OFF types of RGCs in the rabbit retinal explant to five consecutive stimuli with varying inter-stimulus intervals (10-1000 ms). Each stimulus was a 4 ms long monophasic sinusoidal cathodal current, which was applied epiretinally via a conical electrode. Spiking activity of targeted RGCs was recorded using a cell-attached patch electrode. MAIN RESULTS ON and OFF cells had distinct responses to repetitive stimuli. Consistent with earlier studies, OFF cells always generated reduced responses to subsequent stimuli compared to responses to the first stimulus. In contrast, a new stimulus to ON cells suppressed all pending/ongoing responses from previous stimuli and initiated its own response that was remarkably similar to the response from a single stimulus in isolation. This previously unreported 'reset' behavior was observed exclusively and consistently in ON cells. These contrasts between ON and OFF cells created a range of stimulation rates (4-7 Hz) that maximized the ratio of the responses arising in ON versus OFF cells. SIGNIFICANCE Previous clinical testing reported that subjects perceive bright phosphenes (ON responses) and also prefer stimulation rates of 5-7 Hz. Our results suggest that responses of ON cells are weak at high rates of stimulation (> ∼7 Hz) due to the reset while responses of OFF cells are strong at low rates (< ∼4 Hz) due to reduced desensitization, both reducing the ratio of ON to OFF responses. In combination with previous results indicating that responses in ON cells more closely match physiological patterns (Im and Fried 2015 J. Physiol. 593 3577-96), our results offer a potential reason for the user preference of intermediate rates (5-7 Hz).
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Affiliation(s)
- Maesoon Im
- VA Boston Healthcare System, 150 South Huntington Avenue, Boston, MA 02130
- Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, 50 Blossom Street, Boston, MA 02114
| | - Shelley I. Fried
- VA Boston Healthcare System, 150 South Huntington Avenue, Boston, MA 02130
- Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, 50 Blossom Street, Boston, MA 02114
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Goo YS, Park DJ, Ahn JR, Senok SS. Spontaneous Oscillatory Rhythms in the Degenerating Mouse Retina Modulate Retinal Ganglion Cell Responses to Electrical Stimulation. Front Cell Neurosci 2016; 9:512. [PMID: 26793063 PMCID: PMC4709854 DOI: 10.3389/fncel.2015.00512] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 12/21/2015] [Indexed: 11/22/2022] Open
Abstract
Characterization of the electrical activity of the retina in the animal models of retinal degeneration has been carried out in part to understand the progression of retinal degenerative diseases like age-related macular degeneration (AMD) and retinitis pigmentosa (RP), but also to determine optimum stimulus paradigms for use with retinal prosthetic devices. The models most studied in this regard have been the two lines of mice deficient in the β-subunit of phosphodiesterase (rd1 and rd10 mice), where the degenerating retinas exhibit characteristic spontaneous hyperactivity and oscillatory local field potentials (LFPs). Additionally, there is a robust ~10 Hz rhythmic burst of retinal ganglion cell (RGC) spikes on the trough of the oscillatory LFP. In rd1 mice, the rhythmic burst of RGC spikes is always phase-locked with the oscillatory LFP and this phase-locking property is preserved regardless of postnatal ages. However, in rd10 mice, the frequency of the oscillatory rhythm changes according to postnatal age, suggesting that this rhythm might be a marker of the stage of degeneration. Furthermore when a biphasic current stimulus is applied to rd10 mice degenerate retina, distinct RGC response patterns that correlate with the stage of degeneration emerge. This review also considers the significance of these response properties.
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Affiliation(s)
- Yong Sook Goo
- Department of Physiology, Chungbuk National University School of MedicineCheongju, South Korea; Nano Artificial Vision Research Center, Seoul National University HospitalSeoul, South Korea
| | - Dae Jin Park
- Department of Physiology, Chungbuk National University School of MedicineCheongju, South Korea; Nano Artificial Vision Research Center, Seoul National University HospitalSeoul, South Korea
| | - Jung Ryul Ahn
- Department of Physiology, Chungbuk National University School of MedicineCheongju, South Korea; Nano Artificial Vision Research Center, Seoul National University HospitalSeoul, South Korea
| | - Solomon S Senok
- Neuroscience Division, Alfaisal University College of Medicine Riyadh, Saudi Arabia
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Kameneva T, Maturana MI, Hadjinicolaou AE, Cloherty SL, Ibbotson MR, Grayden DB, Burkitt AN, Meffin H. Retinal ganglion cells: mechanisms underlying depolarization block and differential responses to high frequency electrical stimulation of ON and OFF cells. J Neural Eng 2016; 13:016017. [DOI: 10.1088/1741-2560/13/1/016017] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Yang F, Yang CH, Wang FM, Cheng YT, Teng CC, Lee LJ, Yang CH, Fan LS. A high-density microelectrode-tissue-microelectrode sandwich platform for application of retinal circuit study. Biomed Eng Online 2015; 14:109. [PMID: 26611649 PMCID: PMC4662037 DOI: 10.1186/s12938-015-0106-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 11/23/2015] [Indexed: 01/05/2023] Open
Abstract
Background Microelectrode array (MEA) devices are frequently used in neural circuit studies, especially in retinal prosthesis. For a high throughput stimulation and recording paradigm, it is desirable to obtain the responses of multiple surface RGCs initiated from the electrical signals delivered to multiple photoreceptor cells. This can be achieved by an high density MEA-tissue-MEA (MTM) sandwich configuration. However, the retina is one of the most metabolically active tissues, consumes oxygen as rapidly as the brain. The major concern of the MTM configuration is the supply of oxygen. Methods We aimed to develop a high density MTM sandwich platform which consists of stacks of a stimulation MEA, retinal tissue and a recording MEA. Retina is a metabolically active tissue and the firing rate is very sensitive to oxygen level. We designed, simulated and microfabricated porous high density MEAs and an adjustable perfusion system that electrical signals can be delivered to and recorded from the clipped retinal tissue. Results The porous high-density MEAs linked with stimulation or recording devices within a perfusion system were manufactured and the MTM platform was assembled with a retina slice inside. The firing rate remained constant between 25 and 55 min before dramatically declined, indicating that within certain period of time (e.g. 30 min after habituation), the retina condition was kept by sufficient oxygen supply via the perfusion holes in the MEAs provided by the double perfusion system. Conclusions MTM sandwich structure is an efficient platform to study the retinal neural circuit. The material and arrangement of high density microelectrodes with porous design make this MEA appropriate for sub-retina prosthesis. Finding ways to prolong the recording time and reduce the signal-to-noise ratio are important to improve our MTM prototype.
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Affiliation(s)
- Frank Yang
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Chung-Hua Yang
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Fu-Min Wang
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Ya-Ting Cheng
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Chih-Ciao Teng
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Li-Jen Lee
- Graduated Institute of Anatomy and Cell Biology, National Taiwan University, Taipei, Taiwan
| | - Chang-Hao Yang
- Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan
| | - Long-Sheng Fan
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan.
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Im M, Fried SI. Indirect activation elicits strong correlations between light and electrical responses in ON but not OFF retinal ganglion cells. J Physiol 2015; 593:3577-96. [PMID: 26033477 PMCID: PMC4560585 DOI: 10.1113/jp270606] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 05/15/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS To improve the quality of vision elicited by retinal prosthetics, elicited neural activity should resemble physiological signalling patterns; here, we hypothesized that electric stimulation that activates the synaptic circuitry of the retina would lead to closer matches than that which activates ganglion cells directly. We evaluated this hypothesis by comparing light and electrical responses in different types of ganglion cells. In contrast to the similarity in their light responses, electrical responses in ON and OFF cells of the same type were quite distinct. Further, electrical and light responses in the same cell were much better correlated in ON vs. OFF ganglion cells. Stimuli that activated photoreceptors yielded better correlations than those which activated bipolar cells. Our results suggest that the closer match to physiology in the ON signal transmitted to the brain may help to explain preferential reports of 'bright' phosphenes during earlier clinical trials. ABSTRACT To improve the efficacy of microelectronic retinal prosthetics it will be necessary to better understand the response of retinal neurons to electric stimulation. While stimulation that directly activates ganglion cells generally has the lowest threshold, the similarity in responsiveness across cells makes it extremely difficult for such an approach to re-create cell-type specific patterns of neural activity that arise normally in the healthy retina. In contrast, stimulation that activates neurons presynaptic to ganglion cells utilizes at least some of the existing retinal circuitry and therefore is thought to produce neural activity that better matches physiological signalling. Surprisingly, the actual benefit(s) of this approach remain unsubstantiated. Here, we recorded from ganglion cells in the rabbit retinal explant in response to electrical stimuli that activated the network. Targeted cells were first classified into known types via light responses so that the consistency of electrical responses within individual types could be evaluated. Both transient and sustained ON ganglion cells exhibited highly consistent electrical response patterns which were distinct from one another. Further, properties of the response (interspike interval, latency, peak firing rate, and spike count) in a given cell were well correlated to the corresponding properties of the light response for that same cell. Electric responses in OFF ganglion cells formed two groups, distinct from ON groups, and the correlation levels between electric and light responses were much weaker. The closer match in ON pathway responses may help to explain some preferential reporting of bright stimuli during psychophysical testing.
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Affiliation(s)
- Maesoon Im
- Veterans Affairs Boston Healthcare System, 150 South Huntington Avenue, Boston, MA, 02130, USA
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, 50 Blossom Street, Boston, MA, 02114, USA
| | - Shelley I Fried
- Veterans Affairs Boston Healthcare System, 150 South Huntington Avenue, Boston, MA, 02130, USA
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, 50 Blossom Street, Boston, MA, 02114, USA
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O'Brien EE, Greferath U, Fletcher EL. The effect of photoreceptor degeneration on ganglion cell morphology. J Comp Neurol 2014; 522:1155-70. [PMID: 24519018 DOI: 10.1002/cne.23487] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 09/23/2013] [Accepted: 10/02/2013] [Indexed: 11/08/2022]
Abstract
Retinitis pigmentosa refers to a family of inherited photoreceptor degenerations resulting in blindness. During and after photoreceptor loss, neurons of the inner retina are known to undergo plastic changes. Here, we have investigated in detail whether ganglion cells are altered at late stages of degeneration, well after the total loss of photoreceptors. We used mice, rd1-Thy1, that carry a mutation in the β-subunit of phosphodiesterase 6 and a fluorescent protein that labels a subset of ganglion cells and B6-Thy1 control mice. Retinal wholemounts from mice aged 3-11 months were processed for immunohistochemistry and analyzed. Ganglion cells were classified based on soma area, dendritic field size, and branching of dendrites. The dendritic fields of some ganglion cells were further analyzed for their length, area and quantity of branching points. There was a decrease in size and level of branching of A2, B1, and D type ganglion cells in the degenerated retina at 11 months of age. In contrast, C1 ganglion cells remained unchanged. In addition, there was a shift in the proportion of ganglion cells ramifying in the different layers of the inner plexiform layer. Careful analysis of the dendrites of ganglion cells revealed some projecting to new, more distal regions of the inner plexiform layer. We propose that these changes in ganglion cell morphology could impact the function of individual cells as well as the retinal circuitry in the degenerated retina.
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Affiliation(s)
- E E O'Brien
- Department of Anatomy and Neuroscience, University of Melbourne, Melbourne, Victoria, 3010, Australia
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Sim SL, Szalewski RJ, Johnson LJ, Akah LE, Shoemaker LE, Thoreson WB, Margalit E. Simultaneous recording of mouse retinal ganglion cells during epiretinal or subretinal stimulation. Vision Res 2014; 101:41-50. [PMID: 24863584 PMCID: PMC4437194 DOI: 10.1016/j.visres.2014.05.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 04/28/2014] [Accepted: 05/12/2014] [Indexed: 10/25/2022]
Abstract
We compared response patterns and electrical receptive fields (ERF) of retinal ganglion cells (RGCs) during epiretinal and subretinal electrical stimulation of isolated mouse retina. Retinas were stimulated with an array of 3200 independently controllable electrodes. Four response patterns were observed: a burst of activity immediately after stimulation (Type I cells, Vision Research (2008), 48, 1562-1568), delayed bursts beginning >25ms after stimulation (Type II), a combination of both (Type III), and inhibition of ongoing spike activity. Type I responses were produced more often by epiretinal than subretinal stimulation whereas delayed and inhibitory responses were evoked more frequently by subretinal stimulation. Response latencies were significantly shorter with epiretinal than subretinal stimulation. These data suggest that subretinal stimulation is more effective at activating intraretinal circuits than epiretinal stimulation. There was no significant difference in charge threshold between subretinal and epiretinal configurations. ERFs were defined by the stimulating array surface area that successfully stimulated spikes in an RGC. ERFs were complex in shape, similar to receptive fields mapped with light. ERF areas were significantly smaller with subretinal than epiretinal stimulation. This may reflect the greater distance between stimulating electrodes and RGCs in the subretinal configuration. ERFs for immediate and delayed responses mapped within the same Type III cells differed in shape and size, consistent with different sites and mechanisms for generating these two response types.
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Affiliation(s)
- S L Sim
- Department of Ophthalmology and Visual Science, University of Nebraska Medical Center, Omaha, NE, USA
| | - R J Szalewski
- Department of Ophthalmology and Visual Science, University of Nebraska Medical Center, Omaha, NE, USA
| | - L J Johnson
- Naval Research Laboratory, Washington, DC, USA
| | - L E Akah
- Department of Ophthalmology and Visual Science, University of Nebraska Medical Center, Omaha, NE, USA
| | - L E Shoemaker
- Department of Ophthalmology and Visual Science, University of Nebraska Medical Center, Omaha, NE, USA
| | - W B Thoreson
- Department of Ophthalmology and Visual Science, University of Nebraska Medical Center, Omaha, NE, USA; Department of Pharmacology and Experimental Neuroscience, University of Nebraska, NE, USA
| | - E Margalit
- VA Nebraska-Western Iowa Health Care System, NE, USA; Department of Ophthalmology and Visual Science, University of Nebraska Medical Center, Omaha, NE, USA.
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Fransen JW, Pangeni G, Pardue MT, McCall MA. Local signaling from a retinal prosthetic in a rodent retinitis pigmentosa model in vivo. J Neural Eng 2014; 11:046012. [PMID: 24940618 DOI: 10.1088/1741-2560/11/4/046012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE In clinical trials, retinitis pigmentosa patients implanted with a retinal prosthetic device show enhanced spatial vision, including the ability to read large text and navigate. New prosthetics aim to increase spatial resolution by decreasing pixel/electrode size and limiting current spread. To examine spatial resolution of a new prosthetic design, we characterized and compared two photovoltaic array (PVA) designs and their interaction with the retina after subretinal implantation in transgenic S334ter line 3 rats (Tg S334ter-3). APPROACH PVAs were implanted subretinally at two stages of degeneration and assessed in vivo using extracellular recordings in the superior colliculus (SC). Several aspects of this interaction were evaluated by varying duration, irradiance and position of a near infrared laser focused on the PVA. These characteristics included: activation threshold, response linearity, SC signal topography and spatial localization. The major design difference between the two PVA designs is the inclusion of local current returns in the newer design. MAIN RESULTS When tested in vivo, PVA-evoked response thresholds were independent of pixel/electrode size, but differ between the new and old PVA designs. Response thresholds were independent of implantation age and duration (⩽7.5 months). For both prosthesis designs, threshold intensities were within established safety limits. PVA-evoked responses require inner retina synaptic transmission and do not directly activate retinal ganglion cells. The new PVA design evokes local retinal activation, which is not found with the older PVA design that lacks local current returns. SIGNIFICANCE Our study provides in vivo evidence that prosthetics make functional contacts with the inner nuclear layer at several stages of degeneration. The new PVA design enhances local activation within the retina and SC. Together these results predict that the new design can potentially harness the inherent processing within the retina and is likely to produce higher spatial resolution in patients.
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Affiliation(s)
- James W Fransen
- Department of Anatomical Sciences and Neurobiology, University of Louisville, KY 40202, USA
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Abstract
Retinal prosthesis has been translated from the laboratory to the clinic over the past two decades. Currently, two devices have regulatory approval for the treatment of retinitis pigmentosa. These devices provide partial sight restoration and patients use this improved vision in their everyday lives. Improved mobility and object detection are some of the more notable findings from the clinical trials. However, significant vision restoration will require both better technology and improved understanding of the interaction between electrical stimulation and the retina. This paper reviews the recent clinical trials and highlights technology breakthroughs that will contribute to next generation of retinal prostheses.
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Velikay-Parel M, Ivastinovic D, Georgi T, Richard G, Hornig R. A test method for quantification of stimulus-induced depression effects on perceptual threshold in epiretinal prosthesis. Acta Ophthalmol 2013; 91:e595-602. [PMID: 24112756 DOI: 10.1111/aos.12179] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE As part of a clinical trial, an investigational epiretinal implant (IMI Intelligent Medical Implant) was implanted in a retinitis pigmentosa patient. The prosthesis was wirelessly controlled by a visual interface containing a microcamera, providing wireless data and energy transmission. Forty-nine (49) electrodes were used for pattern recognition. This study examined the changes of perceptual thresholds over time and its relation to long-term stimulation. The goal of the study was to introduce stimulus-related depression of perceptual threshold (StirDepth) measurements as a method to gain further insight into the safety profile of electrical stimulation. METHODS The perceptual threshold was defined as the level of stimulation intensity at which a phosphene perception with a probability of 50% was detected using the Best-PEST method. StirDepth was measured by comparing the threshold changes immediately before and after a stimulation session of using three active electrodes and one passive electrode, which served as control. RESULTS The initial threshold of the day remained stable over the observed period. In StirDepth measurement all thresholds raised significantly after the stimulation sessions. The threshold increase of the active electrodes never exceeded that of the inactive control electrode. CONCLUSIONS StirDepth measurement is feasible in epiretinal implants. The prolonged stimulation raised no safety concerns in the patient. The threshold increase of both the active electrodes and the control electrode leads one to hypothesise that cognitive or neurophysiological effects are the cause rather than the desensitizing of the retinal network or incipient retinal damage.
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Affiliation(s)
- Michaela Velikay-Parel
- Department of Ophthalmology, Medical University Graz, Graz, AustriaDepartment of Ophthalmology, University Medical Center Hamburg-Eppendorf, Hamburg, GermanyIMI Intelligent Medical Implants GmbH, Bonn, Germany
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The Argus™ II retinal prosthesis: Factors affecting patient selection for implantation. Prog Retin Eye Res 2013; 36:1-23. [DOI: 10.1016/j.preteyeres.2013.01.002] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 12/20/2012] [Accepted: 01/04/2013] [Indexed: 01/20/2023]
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Savage CO, Kameneva T, Grayden DB, Meffin H, Burkitt AN. Minimisation of required charge for desired neuronal spike rate. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2012:3009-12. [PMID: 23366558 DOI: 10.1109/embc.2012.6346597] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Retinal implants restore limited visual perception to blind implantees by electrical stimulation of surviving neurons. We consider the efficacy of two electrical stimulation parameters, frequency of stimulation and interphase gap between cathodic and anodic phases, on the required charge to reach a desired neuronal spike rate. Using a Hodgkin-Huxley model of a neuron, we find the most efficient means of achieving a desired spike rate for neurons by electrical stimulation is to use a stimulation frequency identical to the desired spike rate, as well as a long interphase gap.
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Affiliation(s)
- Craig O Savage
- NeuroEngineering Laboratory, Department of Electrical and Electronic Engineering, The University of Melbourne, VIC 3010 Australia.
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Cameron MA, Suaning GJ, Lovell NH, Morley JW. Electrical stimulation of inner retinal neurons in wild-type and retinally degenerate (rd/rd) mice. PLoS One 2013; 8:e68882. [PMID: 23874798 PMCID: PMC3708954 DOI: 10.1371/journal.pone.0068882] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Accepted: 05/31/2013] [Indexed: 11/19/2022] Open
Abstract
Electrical stimulation of the retina following photoreceptor degeneration in diseases such as retinitis pigmentosa and age-related macular degeneration has become a promising therapeutic strategy for the restoration of vision. Many retinal neurons remain functional following photoreceptor degeneration; however, the responses of the different classes of cells to electrical stimuli have not been fully investigated. Using whole-cell patch clamp electrophysiology in retinal slices we investigated the response to electrical stimulation of cells of the inner nuclear layer (INL), pre-synaptic to retinal ganglion cells, in wild-type and retinally degenerate (rd/rd) mice. The responses of these cells to electrical stimulation were extremely varied, with both extrinsic and intrinsic evoked responses observed. Further examination of the intrinsically evoked responses revealed direct activation of both voltage-gated Na+ channels and K+ channels. The expression of these channels, which is particularly varied between INL cells, and the stimulus intensity, appears to dictate the polarity of the eventual response. Retinally degenerate animals showed similar responses to electrical stimulation of the retina to those of the wild-type, but the relative representation of each response type differed. The most striking difference between genotypes was the existence of a large amplitude oscillation in the majority of INL cells in rd/rd mice (as previously reported) that impacted on the signal to noise ratio following electrical stimulation. This confounding oscillation may significantly reduce the efficacy of electrical stimulation of the degenerate retina, and a greater understanding of its origin will potentially enable it to be dampened or eliminated.
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Affiliation(s)
- Morven A Cameron
- School of Medicine, the University of Western Sydney, Campbelltown, New South Wales, Australia.
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Focal electrical stimulation of major ganglion cell types in the primate retina for the design of visual prostheses. J Neurosci 2013; 33:7194-205. [PMID: 23616529 DOI: 10.1523/jneurosci.4967-12.2013] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Electrical stimulation of retinal neurons with an advanced retinal prosthesis may eventually provide high-resolution artificial vision to the blind. However, the success of future prostheses depends on the ability to activate the major parallel visual pathways of the human visual system. Electrical stimulation of the five numerically dominant retinal ganglion cell types was investigated by simultaneous stimulation and recording in isolated peripheral primate (Macaca sp.) retina using multi-electrode arrays. ON and OFF midget, ON and OFF parasol, and small bistratified ganglion cells could all be activated directly to fire a single spike with submillisecond latency using brief pulses of current within established safety limits. Thresholds for electrical stimulation were similar in all five cell types. In many cases, a single cell could be specifically activated without activating neighboring cells of the same type or other types. These findings support the feasibility of direct electrical stimulation of the major visual pathways at or near their native spatial and temporal resolution.
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Abstract
OBJECTIVE High-rate pulse trains have proven to be effective in cochlear prosthetics and, more recently, have been shown to elicit a wide range of interesting response properties in axons of the peripheral nervous system. Surprisingly, the effectiveness of such trains for use in retinal prostheses has not been explored. APPROACH Using cell-attached patch clamp methods, we measured the in vitro response of two rabbit retinal ganglion cell types, OFF-brisk transient (OFF-BT) and ON-OFF directionally selective (DS), to trains of biphasic pulses delivered at 2000 pulses per second (PPS). MAIN RESULTS For OFF-BT cells, response onset occurred at ~20 µA, and maximum response occurred at ~40 µA. Interestingly, spiking levels decreased for further increases in amplitude. In contrast, DS cells had a spiking onset at ~25 µA and maintained strong spiking as stimulus amplitude was increased, even at the highest levels tested. Thus, a low-amplitude stimulus train at 2000 PPS (~25 µA) will activate OFF-BT cells strongly, while simultaneously activating DS cells only weakly. In contrast, a high amplitude train (~75 µA) will activate DS cells strongly while suppressing responses in OFF-BT cells. SIGNIFICANCE The response differences between cell types suggest some forms of preferential activation may be possible, and further testing is warranted. Further, the scope of the response differences found here suggests activation mechanisms that are more complex than those described in previous studies.
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Affiliation(s)
- Changsi Cai
- VA Boston Healthcare System, Boston, MA, USA
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Ahuja AK, Yeoh J, Dorn JD, Caspi A, Wuyyuru V, McMahon MJ, Humayun MS, Greenberg RJ, Dacruz L. Factors Affecting Perceptual Threshold in Argus II Retinal Prosthesis Subjects. Transl Vis Sci Technol 2013; 2:1. [PMID: 24049718 DOI: 10.1167/tvst.2.4.1] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Accepted: 01/31/2013] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The Argus II epiretinal prosthesis has been developed to provide partial restoration of vision to subjects blinded from outer retinal degenerative disease. Participants were surgically implanted with the system in the United States and Europe in a single arm, prospective, multicenter clinical trial. The purpose of this investigation was to determine which factors affect electrical thresholds in order to inform surgical placement of the device. METHODS Electrode-retina and electrode-fovea distances were determined using SD-OCT and fundus photography, respectively. Perceptual threshold to electrical stimulation of electrodes was measured using custom developed software, in which current amplitude was varied until the threshold was found. Full field stimulus light threshold was measured using the Espion D-FST test. Relationships between electrical threshold and these three explanatory variables (electrode-retina distance, electrode-fovea distance, and monocular light threshold) were quantified using regression. RESULTS Regression analysis showed a significant correlation between electrical threshold and electrode-retina distance (R2 = 0.50, P = 0.0002; n = 703 electrodes). 90.3% of electrodes in contact with the macula (n = 207) elicited percepts at charge densities less than 1 mC/cm2/phase. These threshold data also correlated well with ganglion cell density profile (P = 0.03). A weaker, but still significant, inverse correlation was found between light threshold and electrical threshold (R2 < 0.52, P = 0.01). Multivariate modeling indicated that electrode-retina distance and light threshold are highly predictive of electrode threshold (R2 = 0.87; P < 0.0005). CONCLUSIONS Taken together, these results suggest that while light threshold should be used to inform patient selection, macular contact of the array is paramount. TRANSLATIONAL RELEVANCE Reported Argus II clinical study results are in good agreement with prior in vitro and in vivo studies, and support the development of higher-density systems that employ smaller diameter electrodes. (clinicaltrials.gov identifier: NCT00407602).
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Affiliation(s)
- A K Ahuja
- Second Sight Medical Products, Inc., Sylmar, CA ; Doheny Eye Institute, Keck School of Medicine, Los Angeles, CA
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Lee SW, Eddington DK, Fried SI. Responses to pulsatile subretinal electric stimulation: effects of amplitude and duration. J Neurophysiol 2013; 109:1954-68. [PMID: 23343891 DOI: 10.1152/jn.00293.2012] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In working to improve the quality of visual percepts elicited by retinal prosthetics, considerable effort has been made to understand how retinal neurons respond to electric stimulation. Whereas responses arising from direct activation of retinal ganglion cells have been well studied, responses arising through indirect activation (e.g., secondary to activation of bipolar cells) are not as well understood. Here, we used cell-attached, patch-clamp recordings to measure the responses of rabbit ganglion cells in vitro to a wide range of stimulus-pulse parameters (amplitudes: 0-100 μA; durations: 0.1-50 ms), applied to a 400-μm-diameter, subretinal-stimulating electrode. The indirect responses generally consisted of multiple action potentials that were clustered into bursts, although the latency and number of spikes within a burst were highly variable. When different parameter pairs representing identical charge levels were compared, the shortest pulse durations generally elicited the most spikes. In addition, latencies were shortest, and jitter was lowest for short pulses. These findings suggest that short pulses are optimum for activation of presynaptic neurons, and therefore, short pulses are more effective for both direct as well as indirect activation.
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Affiliation(s)
- Seung Woo Lee
- Center for Innovative Visual Rehabilitation, Veterans Affairs Boston Healthcare System, Boston, MA, USA
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Eiber CD, Lovell NH, Suaning GJ. Attaining higher resolution visual prosthetics: a review of the factors and limitations. J Neural Eng 2013; 10:011002. [PMID: 23337266 DOI: 10.1088/1741-2560/10/1/011002] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Visual prosthetics is an expanding subfield of functional electrical stimulation which has gained increased interest recently in light of new advances in treatments and technology. These treatments and technology represent a major improvement over prior art, but are still subject to a host of limitations which are dependent on the manner in which one approaches the topic of visual prosthetics. These limitations pose new research challenges whose solutions are directly applicable to the well-being of blind individuals everywhere. In this review, we will outline and critically compare major current approaches to visual prosthetics, and in particular retinal prosthetics. Then, we will engage in an in-depth discussion of the limitations imposed by current technology, physics, and the underlying biology of the retina to highlight several of the challenges currently facing researchers.
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Affiliation(s)
- Calvin D Eiber
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW 2052, Australia.
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Damiani D, Novelli E, Mazzoni F, Strettoi E. Undersized dendritic arborizations in retinal ganglion cells of the rd1 mutant mouse: a paradigm of early onset photoreceptor degeneration. J Comp Neurol 2012; 520:1406-23. [PMID: 22102216 DOI: 10.1002/cne.22802] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Retinitis pigmentosa (RP) is a family of inherited diseases causing progressive photoreceptor death. Retinal ganglion cells (RGCs) form the biological substrate for various therapeutic approaches designed to restore vision in RP individuals. Assessment of survival and preservation of RGCs in animal paradigms mimicking the human disease is of key importance for appropriate implementation of vision repair strategies. Here we studied the survival of RGCs in the rd1 mutant mouse, a known model of early onset, autosomic recessive RP, at various stages of photoreceptor degeneration. Furthermore, we analyzed the morphology of various types of RGCs using the newly generated transgenic mouse rd1/Thy1-GFP, in which the rd1 mutation is associated with green fluorescent protein (GFP) expression in a small population of different RGCs. We found excellent survival of cells at up to 1 year of age, a time at which the inner retina is known to have severely reorganized and partially degenerated. However, 50% of the cells analyzed within all RGC types exhibit an undersized dendritic tree, spanning about half of the normal area. Undersized cells are found both in adult and in very young (1-month-old) mice. This suggests that their aberrant phenotype is due to incomplete dendritic development, possibly as a consequence of altered visual input at the time of dendritic arbor refinement. These data show the importance of the timing of photoreceptor death in RGC dendritic development.
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Affiliation(s)
- Devid Damiani
- Neuroscience Institute, National Research Council of Italy, CNR, Pisa, Italy
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Luo J, Boosalis BJ, Thoreson WB, Margalit E. A comparison of optical and electrophysiological methods for recording retinal ganglion cells during electrical stimulation. Curr Eye Res 2012; 37:218-27. [PMID: 22335809 DOI: 10.3109/02713683.2011.652756] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE/AIM To compare the efficacy of optical techniques with electrophysiological recordings for mapping retinal activity in response to electrical stimulation. MATERIALS AND METHODS Whole cell patch clamp, Ca(2+) imaging (Fluo-4-AM), and Na(+) imaging (CoroNa Green-AM) techniques were used to detect responses of neurons from mouse and salamander retina to electrical stimulation. RESULTS Synaptic currents were observed in ≥23% of retinal ganglion cells (RGCs), indicating presynaptic Ca(2+) increases in the inner plexiform layer (IPL). Modest depolarization with 20-30 mM K(+) consistently evoked Ca(2+) responses measured with Fluo4, but Ca(2+) responses were almost never evoked by epiretinal stimulation. In salamander retina, responses were seen in the inner nuclear layer (INL) and IPL. In mouse retina, responses were also sometimes seen in the outer pexiform layer (OPL). OPL responses showed a longer latency than IPL responses, suggesting that outer retinal circuits do not trigger synaptic responses of RGCs. Simultaneous Ca(2+) imaging and electrophysiological recording of synaptic currents confirmed that Fluo4-loaded retinas remained responsive to stimulation. Epiretinal stimulation evoked action potentials in ≥67% of RGCs. CoroNa Green detected Na(+) changes stimulated by 20 mM K(+), but epiretinal stimulation did not evoke detectable Na(+) responses. Simultaneous imaging and electrophysiological recording confirmed the health of CoroNa Green-loaded retinas. We confirmed stimulation efficacy by simultaneously recording Na(+) changes and electrophysiological responses. CONCLUSIONS These data demonstrate that electrophysiological recordings show greater sensitivity than Na(+) or Ca(2+) imaging in response to electrical stimulation. The paucity of Ca(2+) responses is consistent with limited risk for Ca(2+)-mediated cell damage during electrical stimulation.
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Affiliation(s)
- Jianmin Luo
- Department of Ophthalmology and Visual Science, University of Nebraska Medical Center, Omaha, NE 68198, USA
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Goo YS, Ahn KN, Song YJ, Ryu SB, Kim KH. Comparison of basal oscillatory rhythm of retinal activities in rd1 and rd10 mice. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:1093-6. [PMID: 22254504 DOI: 10.1109/iembs.2011.6090255] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Among the many animal models of retinitis pigmentosa (RP), the most extensively characterized animal is the rd1 mouse. Recent studies showed that the neurophysiological properties of rd1 retinas differ significantly from those of normal retina; the presence of an oscillatory rhythmic activity (~10 Hz) both in retinal ganglion cell (RGC) spikes and field potentials (slow wave component, SWC). However, lesser studies have been done regarding electrical characteristics of rd10 retina, carrying the mutation of same rod-PDE gene and showing a later onset degeneration of photoreceptors. Therefore, in this study, we compared the oscillatory rhythm in RGC spike and SWC between rd1 and rd10 mice in different postnatal ages to understand neural code used by two diseased retinas to communicate with the brain. Extracellular action potentials are recorded by 8 × 8 MEA from the RGC in the in vitro whole mount retina. 4 and 8 weeks in rd1 mice and 4, 10, 15, and 20 weeks in rd10 mice were used (n=3 for each postnatal age). From the raw waveform of retinal recording, RGC Spikes and SWC were isolated by using 200 Hz high-pass filter and 20 Hz low-pass filter, respectively. Fourier transform was performed for detection of oscillatory rhythm in RGC spikes and SWC. In rd1 mice, there is no statistical difference between the frequency of SWC and spike in 4 weeks [p>0.05; spike 9.3 ± 0.9 Hz (n=40), SWC 9.3 ± 1.5 Hz (n=25)] and 8 weeks [p>0.05; spike 10.0 ± 1.3 Hz (n=87), SWC 10.9 ± 1.7 Hz (n=25)]. While in rd10 mice there is no statistical differences among the SWC through 4 ~ 20 weeks, significant differences were observed between the frequency of RGC spike and SWC and also among RGC spikes [4 weeks (p<0.001): spike 5.5 ± 1.3 Hz (n=59), SWC 10.8 ± 3.1 Hz (n=14); 10 weeks (p<0.001): spike 6.8 ± 3.8 Hz (n=79), SWC 10.3 ± 2.6 Hz (n=25); 15 weeks (p<0.05): spike 3.9 ± 0.7 Hz (n=33), SWC 9.9 ± 1.2 Hz (n=25); 20 weeks (p<0.05): spike 4.4 ± 1.2 Hz (n=53), SWC 9.8 ± 1.2 Hz (n=25)].
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Affiliation(s)
- Yong Sook Goo
- department of Physiology, Chungbuk National University School of Medicine, Cheongju 361-763, Republic ofKorea.
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