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Azrad Leibovitch T, Farah N, Markus A, Mandel Y. A novel GCaMP6f-RCS rat model for studying electrical stimulation in the degenerated retina. Front Cell Dev Biol 2024; 12:1386141. [PMID: 38711618 PMCID: PMC11070775 DOI: 10.3389/fcell.2024.1386141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Accepted: 03/25/2024] [Indexed: 05/08/2024] Open
Abstract
Background: Retinal prostheses aim to restore vision by electrically stimulating the remaining viable retinal cells in Retinal Degeneration (RD) cases. Research in this field necessitates a comprehensive analysis of retinal ganglion cells' (RGCs) responses to assess the obtained visual acuity and quality. Here we present a novel animal model which facilitates the optical recording of RGCs activity in an RD rat. This model can significantly enhance the functional evaluation of vision restoration treatments. Methods: The development of the novel rat model is based on crossbreeding a retinal degenerated Royal College of Surgeons (RCS) rat with a transgenic line expressing the genetic calcium indicator GCaMP6f in the RGCs. Characterization of the model was achieved using Optical Coherence Tomography (OCT) imaging, histology, and electroretinography (ERG) at the ages of 4, 8, and 12 weeks. Additionally, optical recordings of RGCs function in response to ex-vivo subretinal electrical stimulations were performed. Results: Histological investigations confirmed the high expression of GCaMP6f in the RGCs and minimal expression in the inner nuclear layer (INL). OCT imaging and histological studies revealed the expected gradual retinal degeneration, as evident by the decrease in retinal thickness with age and the formation of subretinal debris. This degeneration was further confirmed by ERG recordings, which demonstrated a significant decrease in the b-wave amplitude throughout the degeneration process, culminating in its absence at 12 weeks in the GCaMP6f-RCS rat. Importantly, the feasibility of investigating subretinal stimulation was demonstrated, revealing a consistent increase in activation threshold throughout degeneration. Furthermore, an increase in the diameter of the activated area with increasing currents was observed. The spatial spread of the activation area in the GCaMP6f-RCS rat was found to be smaller and exhibited faster activation dynamics compared with the GCaMP6f-LE strain. Conclusion: This novel animal model offers an opportunity to deepen our understanding of prosthetically induced retinal responses, potentially leading to significant advancements in prosthetic interventions in visual impairments.
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Affiliation(s)
- Tamar Azrad Leibovitch
- Bar Ilan Institute for Nanotechnology and Advanced Materials (BINA), Bar Ilan University, Ramat Gan, Israel
- Faculty of Life Sciences, School of Optometry and Visual Science, Bar Ilan University, Ramat Gan, Israel
| | - Nairouz Farah
- Bar Ilan Institute for Nanotechnology and Advanced Materials (BINA), Bar Ilan University, Ramat Gan, Israel
- Faculty of Life Sciences, School of Optometry and Visual Science, Bar Ilan University, Ramat Gan, Israel
| | - Amos Markus
- Bar Ilan Institute for Nanotechnology and Advanced Materials (BINA), Bar Ilan University, Ramat Gan, Israel
- Faculty of Life Sciences, School of Optometry and Visual Science, Bar Ilan University, Ramat Gan, Israel
| | - Yossi Mandel
- Bar Ilan Institute for Nanotechnology and Advanced Materials (BINA), Bar Ilan University, Ramat Gan, Israel
- Faculty of Life Sciences, School of Optometry and Visual Science, Bar Ilan University, Ramat Gan, Israel
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Li L, Feng X, Fang F, Miller DA, Zhang S, Zhuang P, Huang H, Liu P, Liu J, Sredar N, Liu L, Sun Y, Duan X, Goldberg JL, Zhang HF, Hu Y. Longitudinal in vivo Ca 2+ imaging reveals dynamic activity changes of diseased retinal ganglion cells at the single-cell level. Proc Natl Acad Sci U S A 2022; 119:e2206829119. [PMID: 36409915 PMCID: PMC9889883 DOI: 10.1073/pnas.2206829119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 10/05/2022] [Indexed: 11/22/2022] Open
Abstract
Retinal ganglion cells (RGCs) are heterogeneous projection neurons that convey distinct visual features from the retina to brain. Here, we present a high-throughput in vivo RGC activity assay in response to light stimulation using noninvasive Ca2+ imaging of thousands of RGCs simultaneously in living mice. Population and single-cell analyses of longitudinal RGC Ca2+ imaging reveal distinct functional responses of RGCs and unprecedented individual RGC activity conversions during traumatic and glaucomatous degeneration. This study establishes a foundation for future in vivo RGC function classifications and longitudinal activity evaluations using more advanced imaging techniques and visual stimuli under normal, disease, and neural repair conditions. These analyses can be performed at both the population and single-cell levels using temporal and spatial information, which will be invaluable for understanding RGC pathophysiology and identifying functional biomarkers for diverse optic neuropathies.
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Affiliation(s)
- Liang Li
- Spencer Center for Vision Research, Department of Ophthalmology, Byers Eye Institute at Stanford University School of Medicine, Palo Alto, CA94304
| | - Xue Feng
- Spencer Center for Vision Research, Department of Ophthalmology, Byers Eye Institute at Stanford University School of Medicine, Palo Alto, CA94304
| | - Fang Fang
- Spencer Center for Vision Research, Department of Ophthalmology, Byers Eye Institute at Stanford University School of Medicine, Palo Alto, CA94304
- Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha410011, China
| | - David A. Miller
- Department of Biomedical Engineering, Northwestern University, Evanston, IL60208
| | - Shaobo Zhang
- Department of Ophthalmology, University of California San Francisco, San Francisco, CA94143
| | - Pei Zhuang
- Spencer Center for Vision Research, Department of Ophthalmology, Byers Eye Institute at Stanford University School of Medicine, Palo Alto, CA94304
| | - Haoliang Huang
- Spencer Center for Vision Research, Department of Ophthalmology, Byers Eye Institute at Stanford University School of Medicine, Palo Alto, CA94304
| | - Pingting Liu
- Spencer Center for Vision Research, Department of Ophthalmology, Byers Eye Institute at Stanford University School of Medicine, Palo Alto, CA94304
| | - Junting Liu
- Spencer Center for Vision Research, Department of Ophthalmology, Byers Eye Institute at Stanford University School of Medicine, Palo Alto, CA94304
| | - Nripun Sredar
- Spencer Center for Vision Research, Department of Ophthalmology, Byers Eye Institute at Stanford University School of Medicine, Palo Alto, CA94304
| | - Liang Liu
- Spencer Center for Vision Research, Department of Ophthalmology, Byers Eye Institute at Stanford University School of Medicine, Palo Alto, CA94304
| | - Yang Sun
- Spencer Center for Vision Research, Department of Ophthalmology, Byers Eye Institute at Stanford University School of Medicine, Palo Alto, CA94304
| | - Xin Duan
- Department of Ophthalmology, University of California San Francisco, San Francisco, CA94143
| | - Jeffrey L. Goldberg
- Spencer Center for Vision Research, Department of Ophthalmology, Byers Eye Institute at Stanford University School of Medicine, Palo Alto, CA94304
| | - Hao F. Zhang
- Department of Biomedical Engineering, Northwestern University, Evanston, IL60208
| | - Yang Hu
- Spencer Center for Vision Research, Department of Ophthalmology, Byers Eye Institute at Stanford University School of Medicine, Palo Alto, CA94304
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Carleton M, Oesch NW. Differences in the spatial fidelity of evoked and spontaneous signals in the degenerating retina. Front Cell Neurosci 2022; 16:1040090. [PMID: 36419935 PMCID: PMC9676928 DOI: 10.3389/fncel.2022.1040090] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 10/20/2022] [Indexed: 07/01/2024] Open
Abstract
Vision restoration strategies aim to reestablish vision by replacing the function of lost photoreceptors with optoelectronic hardware or through gene therapy. One complication to these approaches is that retinal circuitry undergoes remodeling after photoreceptor loss. Circuit remodeling following perturbation is ubiquitous in the nervous system and understanding these changes is crucial for treating neurodegeneration. Spontaneous oscillations that arise during retinal degeneration have been well-studied, however, other changes in the spatiotemporal processing of evoked and spontaneous activity have received less attention. Here we use subretinal electrical stimulation to measure the spatial and temporal spread of both spontaneous and evoked activity during retinal degeneration. We found that electrical stimulation synchronizes spontaneous oscillatory activity, over space and through time, thus leading to increased correlations in ganglion cell activity. Intriguingly, we found that spatial selectivity was maintained in rd10 retina for evoked responses, with spatial receptive fields comparable to wt retina. These findings indicate that different biophysical mechanisms are involved in mediating feed forward excitation, and the lateral spread of spontaneous activity in the rd10 retina, lending support toward the possibility of high-resolution vision restoration.
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Affiliation(s)
- Maya Carleton
- Department of Psychology, University of California, San Diego, La Jolla, CA, United States
| | - Nicholas W. Oesch
- Department of Psychology, University of California, San Diego, La Jolla, CA, United States
- Department of Ophthalmology, University of California, San Diego, La Jolla, CA, United States
- The Neurosciences Graduate Program, University of California, San Diego, La Jolla, CA, United States
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4
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Lu Y, Qin S, Zhao L, Yue L, Wu T, Qin B, Xu Z. Optimization of stimulation parameters for epi-retinal implant based on biosafety consideration. PLoS One 2020; 15:e0236176. [PMID: 32697792 PMCID: PMC7375526 DOI: 10.1371/journal.pone.0236176] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 06/30/2020] [Indexed: 11/19/2022] Open
Abstract
Background Optimizing stimulation protocol is essential for clinical application of retinal prosthesis. Elongating stimulation pulse width (~25ms /phase) has been proposed as an effective method to improve spatial resolution of epi-retinal implants. However, it is unknown whether longer stimulus pulse width will increase the risk of damaging the retina. In addition, with the advent of next generation retinal prosthesis featuring high-density microelectrode array, it is tempting to optimizing a single set of parameters for all electrodes instead of optimizing parameters of each electrode, but this approach raised biosafety concern. We sought to study the effect of stimulus pulse width on the response of retinal ganglion cells to electrical stimulation, and evaluate if the single parameter set approach was valid based on biosafety measures. Methods We stimulated mouse retina using biphasic pulse waveform generated by chosen electrodes (single or a 3x3 assembly) from multiple microelectrode arrays, recorded their action potentials and performed spike sorting. We tested various stimulus intensity with two fixed pulse width: a short one for 1 millisecond per phase, and a long one for 25 milliseconds per phase. All these assays were performed on two mouse models: the wildtype C57BL/6J mice and the photoreceptor degenerated rd10 mice. The action-potential-frequency vs stimulus amplitude profiles were plotted, and three parameters were extracted: the threshold (the lowest stimulus amplitude activating RGC units), safety-limit (stimulus amplitude that attenuated the firing rate to half of the maximum response), and the stimulation amplitude range (the difference between threshold and safety limit parameters). Results In single-electrode stimulation experiment, we found that on average 85% of the recorded units showed attenuated response to extreme stimulation; among those units, an average of 51% stopped responding during stimulation ramping and failed to recover after one-hour post-stimulation, indicating extreme stimulation can damage RGC units. Twenty-five-millisecond pulse stimulation significantly reduced safety-limit and stimulation-amplitude-range parameters of recorded RGC units compared to 1ms pulse stimulation. During stimulus amplitude ramping, the maximum proportion of responsive healthy RGC units was 51% on average in 25ms pulse condition, and 76% on average in 1ms pulse condition, indicating long pulse may inflict more strain on RGCs, and a significant amount of inappropriately stimulated RGCs always exist. The contrast of these proportions could be explained by the tight correlation between the threshold and safety-limit parameter in 25ms pulse condition. These results were corroborated by those from 3x3 array stimulation experiments. Conclusion Base on a biosafety measure (RGCs’ evoked firing rate in response to electrical stimulation), we proposed that longer stimulation pulse width could lead to reduced retinal response and thus highlighted the importance of carefully setting the stimulation amplitude in this case. Our results also suggested that optimizing a single set of parameters for all electrodes without individual tweaking always generated a significant amount of inappropriately stimulated RGCs, especially in the long pulse stimulation condition.
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Affiliation(s)
- Yijie Lu
- Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
- Shenzhen Aier Eye Hospital, Shenzhen, China
| | - Shan Qin
- Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
- Shenzhen Shekou People’s Hospital, The Second Xiangya Hospital of Central South University Shenzhen Hospital, Shenzhen, China
| | - Lei Zhao
- Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Lan Yue
- Roski Eye Institute, University of Southern California, Los Angeles, California, United States of America
| | - Tianzhun Wu
- Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Bo Qin
- Shenzhen Aier Eye Hospital, Shenzhen, China
- * E-mail: (ZX); (BQ)
| | - Zhen Xu
- Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
- * E-mail: (ZX); (BQ)
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Kostyuk AI, Kokova AD, Podgorny OV, Kelmanson IV, Fetisova ES, Belousov VV, Bilan DS. Genetically Encoded Tools for Research of Cell Signaling and Metabolism under Brain Hypoxia. Antioxidants (Basel) 2020; 9:E516. [PMID: 32545356 PMCID: PMC7346190 DOI: 10.3390/antiox9060516] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 06/04/2020] [Accepted: 06/06/2020] [Indexed: 02/08/2023] Open
Abstract
Hypoxia is characterized by low oxygen content in the tissues. The central nervous system (CNS) is highly vulnerable to a lack of oxygen. Prolonged hypoxia leads to the death of brain cells, which underlies the development of many pathological conditions. Despite the relevance of the topic, different approaches used to study the molecular mechanisms of hypoxia have many limitations. One promising lead is the use of various genetically encoded tools that allow for the observation of intracellular parameters in living systems. In the first part of this review, we provide the classification of oxygen/hypoxia reporters as well as describe other genetically encoded reporters for various metabolic and redox parameters that could be implemented in hypoxia studies. In the second part, we discuss the advantages and disadvantages of the primary hypoxia model systems and highlight inspiring examples of research in which these experimental settings were combined with genetically encoded reporters.
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Affiliation(s)
- Alexander I. Kostyuk
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia; (A.I.K.); (A.D.K.); (O.V.P.); (I.V.K.); (E.S.F.); (V.V.B.)
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Pirogov Russian National Research Medical University, 117997 Moscow, Russia
| | - Aleksandra D. Kokova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia; (A.I.K.); (A.D.K.); (O.V.P.); (I.V.K.); (E.S.F.); (V.V.B.)
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Pirogov Russian National Research Medical University, 117997 Moscow, Russia
| | - Oleg V. Podgorny
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia; (A.I.K.); (A.D.K.); (O.V.P.); (I.V.K.); (E.S.F.); (V.V.B.)
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Pirogov Russian National Research Medical University, 117997 Moscow, Russia
- Koltzov Institute of Developmental Biology, 119334 Moscow, Russia
| | - Ilya V. Kelmanson
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia; (A.I.K.); (A.D.K.); (O.V.P.); (I.V.K.); (E.S.F.); (V.V.B.)
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Pirogov Russian National Research Medical University, 117997 Moscow, Russia
| | - Elena S. Fetisova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia; (A.I.K.); (A.D.K.); (O.V.P.); (I.V.K.); (E.S.F.); (V.V.B.)
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Pirogov Russian National Research Medical University, 117997 Moscow, Russia
- Faculty of Biology, Lomonosov Moscow State University, 119992 Moscow, Russia
| | - Vsevolod V. Belousov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia; (A.I.K.); (A.D.K.); (O.V.P.); (I.V.K.); (E.S.F.); (V.V.B.)
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Pirogov Russian National Research Medical University, 117997 Moscow, Russia
- Institute for Cardiovascular Physiology, Georg August University Göttingen, D-37073 Göttingen, Germany
- Federal Center for Cerebrovascular Pathology and Stroke, 117997 Moscow, Russia
| | - Dmitry S. Bilan
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia; (A.I.K.); (A.D.K.); (O.V.P.); (I.V.K.); (E.S.F.); (V.V.B.)
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Pirogov Russian National Research Medical University, 117997 Moscow, Russia
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Lyu Q, Lu Z, Li H, Qiu S, Guo J, Sui X, Sun P, Li L, Chai X, Lovell NH. A Three-Dimensional Microelectrode Array to Generate Virtual Electrodes for Epiretinal Prosthesis Based on a Modeling Study. Int J Neural Syst 2020; 30:2050006. [DOI: 10.1142/s0129065720500069] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Despite many advances in the development of retinal prostheses, clinical reports show that current retinal prosthesis subjects can only perceive prosthetic vision with poor visual acuity. A possible approach for improving visual acuity is to produce virtual electrodes (VEs) through electric field modulation. Generating controllable and localized VEs is a crucial factor in effectively improving the perceptive resolution of the retinal prostheses. In this paper, we aimed to design a microelectrode array (MEA) that can produce converged and controllable VEs by current steering stimulation strategies. Through computational modeling, we designed a three-dimensional concentric ring–disc MEA and evaluated its performance with different stimulation strategies. Our simulation results showed that electrode–retina distance (ERD) and inter-electrode distance (IED) can dramatically affect the distribution of electric field. Also the converged VEs could be produced when the parameters of the three-dimensional MEA were appropriately set. VE sites can be controlled by manipulating the proportion of current on each adjacent electrode in a current steering group (CSG). In addition, spatial localization of electrical stimulation can be greatly improved under quasi-monopolar (QMP) stimulation. This study may provide support for future application of VEs in epiretinal prosthesis for potentially increasing the visual acuity of prosthetic vision.
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Affiliation(s)
- Qing Lyu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Zhuofan Lu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Heng Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Shirong Qiu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Jiahui Guo
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Xiaohong Sui
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Pengcheng Sun
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Liming Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Xinyu Chai
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Nigel H. Lovell
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW 2052, Australia
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Tong W, Stamp M, Apollo NV, Ganesan K, Meffin H, Prawer S, Garrett DJ, Ibbotson MR. Improved visual acuity using a retinal implant and an optimized stimulation strategy. J Neural Eng 2019; 17:016018. [DOI: 10.1088/1741-2552/ab5299] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Roy S, Field GD. Dopaminergic modulation of retinal processing from starlight to sunlight. J Pharmacol Sci 2019; 140:86-93. [PMID: 31109761 DOI: 10.1016/j.jphs.2019.03.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 03/13/2019] [Accepted: 03/29/2019] [Indexed: 12/17/2022] Open
Abstract
Neuromodulators such as dopamine, enable context-dependent plasticity of neural circuit function throughout the central nervous system. For example, in the retina, dopamine tunes visual processing for daylight and nightlight conditions. Specifically, high levels of dopamine release in the retina tune vision for daylight (photopic) conditions, while low levels tune it for nightlight (scotopic) conditions. This review covers the cellular and circuit-level mechanisms within the retina that are altered by dopamine. These mechanisms include changes in gap junction coupling and ionic conductances, both of which are altered by the activation of diverse types of dopamine receptors across diverse types of retinal neurons. We contextualize the modulatory actions of dopamine in terms of alterations and optimizations to visual processing under photopic and scotopic conditions, with particular attention to how they differentially impact distinct cell types. Finally, we discuss how transgenic mice and disease models have shaped our understanding of dopaminergic signaling and its role in visual processing. Cumulatively, this review illustrates some of the diverse and potent mechanisms through which neuromodulation can shape brain function.
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Affiliation(s)
- Suva Roy
- Department of Neurobiology, Duke University School of Medicine, Durham, NC, USA
| | - Greg D Field
- Department of Neurobiology, Duke University School of Medicine, Durham, NC, USA.
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Chang YC, Haji Ghaffari D, Chow RH, Weiland JD. Stimulation strategies for selective activation of retinal ganglion cell soma and threshold reduction. J Neural Eng 2019; 16:026017. [PMID: 30560810 PMCID: PMC6648650 DOI: 10.1088/1741-2552/aaf92b] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
OBJECTIVE Retinal prosthetic implants restore partial vision to patients blinded due to outer retinal degeneration, using a camera-guided multielectrode array (MEA) that electrically stimulates surviving retinal neurons. Commercial epi-retinal prostheses use millisecond-scale charge-balanced, symmetric, cathodic-first biphasic pulses to depolarize retinal ganglion cells (RGCs) and bipolar cells (BCs), frequently creating oblong perceptions of light related to axonal activation of RGCs. Stimulation strategies that avoid axonal stimulation and decrease the threshold of targeted neurons may significantly improve prosthetic vision in terms of spatial resolution and power efficiency. APPROACH We developed a virus-transduced genetically encoded calcium indicator (GECI) GCaMP6f and microscopy platform for calcium imaging to record the neural activity from RGCs at single-cell resolution in wholemount retinas. Multiple stimulation paradigms were applied through a microelectrode array (MEA) with transparent indium tin oxide electrodes. The evoked neuronal activities were converted to corresponding 2D calcium imaging transient pattern and spatial threshold map to identify the ideal focal response which corresponds to optimal percept in patient. MAIN RESULTS The proposed optical system with GCaMP6f is capable of recording from population of mouse RGCs in real time during electrical stimulation with precise location information relative to the stimulation sites. Optimal duration and phase order of pulse were identified to avoid axonal stimulation and selectively activate targeted RGC somas, without requiring a significant increase in stimulation charge. Additionally, we show that reduced stimulus threshold can be achieved with the special design of asymmetric anodic-first pulse. SIGNIFICANCE Our findings support the possibility of manipulating the responses of RGCs through varying the stimulation waveform. Focal response can be achieved with relative short duration (⩽120 μs) pulses, and can be improved by reversing the standard phase order. The RGCs threshold can be significantly reduced by 33.3%-50% in terms of charge through applying hyperpolarizing pre-pulses with a 20:1 ratio (pre-pulse:stimulus pulse). The results support the future retinal prosthesis design that potentially forms more ideal shape perception with higher spatial resolution and power efficiency.
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Affiliation(s)
- Yao-Chuan Chang
- Center for Bioelectronic Medicine & Biomedical Science, Feinstein Institute for Medical Research, Manhasset, NY 11030, United States of America
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10
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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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11
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Autophosphorylated CaMKII Facilitates Spike Propagation in Rat Optic Nerve. J Neurosci 2018; 38:8087-8105. [PMID: 30076212 DOI: 10.1523/jneurosci.0078-18.2018] [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: 01/09/2018] [Revised: 07/14/2018] [Accepted: 08/01/2018] [Indexed: 11/21/2022] Open
Abstract
Repeated spike firing can transmit information at synapses and modulate spike timing, shape, and conduction velocity. These latter effects have been found to result from voltage-induced changes in ion currents and could alter the signals carried by axons. Here, we test whether Ca2+/calmodulin-dependent protein kinase II (CaMKII) regulates spike propagation in adult rat optic nerve. We find that small-, medium-, and large-diameter axons bind anti-Thr286-phosphorylated CaMKII (pT286) antibodies and that, in isolated optic nerves, electrical stimulation reduces pT286 levels, spike propagation is hastened by CaMKII autophosphorylation and slowed by CaMKII dephosphorylation, single and multiple spikes slow propagation of subsequently activated spikes, and more frequent stimulation produces greater slowing. Likewise, exposing freely moving animals to flickering illumination reduces pT286 levels in optic nerves and electrically eliciting spikes in vivo in either the optic nerve or optic chiasm slows subsequent spike propagation in the optic nerve. By increasing the time that elapses between successive spikes as they propagate, pT286 dephosphorylation and activity-induced spike slowing reduce the frequency of propagated spikes below the frequency at which they were elicited and would thus limit the frequency at which axons synaptically drive target neurons. Consistent with this, the ability of retinal ganglion cells to drive at least some lateral geniculate neurons has been found to increase when presented with light flashes at low and moderate temporal frequencies but less so at high frequencies. Activity-induced decreases in spike frequency may also reduce the energy required to maintain normal intracellular Na+ and Ca2+ levels.SIGNIFICANCE STATEMENT By propagating along axons at constant velocities, spikes could drive synapses as frequently as they are initiated. However, the onset of spiking has been found to alter the conduction velocity of subsequent ("follower") spikes in various preparations. Here, we find that spikes reduce spike frequency in rat optic nerve by slowing follower spike propagation and that electrically stimulated spiking ex vivo and spike-generating flickering illumination in vivo produce net decreases in axonal Ca2+/calmodulin-dependent protein kinase II (CaMKII) autophosphorylation. Consistent with these effects, propagation speed increases and decreases, respectively, with CaMKII autophosphorylation and dephosphorylation. Lowering spike frequency by CaMKII dephosphorylation is a novel consequence of axonal spiking and light adaptation that could decrease synaptic gain as stimulus frequency increases and may also reduce energy use.
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12
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Yang CY, Tsai D, Guo T, Dokos S, Suaning GJ, Morley JW, Lovell NH. Differential electrical responses in retinal ganglion cell subtypes: effects of synaptic blockade and stimulating electrode location. J Neural Eng 2018; 15:046020. [PMID: 29737971 DOI: 10.1088/1741-2552/aac315] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Visual prostheses have shown promising results in restoring visual perception to blind patients. The ability to differentially activate retinal ganglion cell (RGC) subtypes could further improve the efficacy of these medical devices. APPROACH Using whole-cell patch clamp, we investigated membrane potential differences between ON and OFF RGCs in the mouse retina when their synaptic inputs were blocked by synaptic blockers, and examined the differences in stimulation thresholds under such conditions. By injecting intracellular current, we further confirmed the relationship between RGC stimulation thresholds and resting membrane potentials (RMPs). In addition, we investigated the effects of stimulating electrode location on the differences in stimulation thresholds between ON and OFF RGCs. MAIN RESULTS With synaptic blockade, ON RGCs became significantly more hyperpolarized (from -61.8 ± 1.4 mV to -70.8 ± 1.6 mV), while OFF RGCs depolarized slightly (from -60.5 ± 0.7 mV to -58.6 ± 0.9 mV). RGC stimulation thresholds were negatively correlated with their RMPs (Pearson r value: -0.5154; p-value: 0.0042). Thus, depriving ON RGCs of synaptic inputs significantly increased their thresholds (from 14.7 ± 1.3 µA to 22.3 ± 2.1 µA) over those of OFF RGCs (from 13.2 ± 0.7 µA to 13.1 ± 1.1 µA). However, with control solution, ON and OFF RGC stimulation thresholds were not significantly different. Finally, placement of the stimulating electrode away from the axon enhanced differences in stimulation thresholds between ON and OFF RGCs, facilitating preferential activation of OFF RGCs. SIGNIFICANCE Since ON and OFF RGCs have antagonistic responses to natural light, achieving differential RGC activation could convey more natural visual information, leading to better visual prosthesis outcomes.
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Affiliation(s)
- Chih Yu Yang
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW 2052, Australia
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13
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Esler TB, Kerr RR, Tahayori B, Grayden DB, Meffin H, Burkitt AN. Minimizing activation of overlying axons with epiretinal stimulation: The role of fiber orientation and electrode configuration. PLoS One 2018; 13:e0193598. [PMID: 29494655 PMCID: PMC5833203 DOI: 10.1371/journal.pone.0193598] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2017] [Accepted: 02/14/2018] [Indexed: 12/19/2022] Open
Abstract
Currently, a challenge in electrical stimulation of the retina with a visual prosthesis (bionic eye) is to excite only the cells lying directly under the electrode in the ganglion cell layer, while avoiding excitation of axon bundles that pass over the surface of the retina in the nerve fiber layer. Stimulation of overlying axons results in irregular visual percepts, limiting perceptual efficacy. This research explores how differences in fiber orientation between the nerve fiber layer and ganglion cell layer leads to differences in the electrical activation of the axon initial segment and axons of passage. Approach. Axons of passage of retinal ganglion cells in the nerve fiber layer are characterized by a narrow distribution of fiber orientations, causing highly anisotropic spread of applied current. In contrast, proximal axons in the ganglion cell layer have a wider distribution of orientations. A four-layer computational model of epiretinal extracellular stimulation that captures the effect of neurite orientation in anisotropic tissue has been developed using a volume conductor model known as the cellular composite model. Simulations are conducted to investigate the interaction of neural tissue orientation, stimulating electrode configuration, and stimulation pulse duration and amplitude. Main results. Our model shows that simultaneous stimulation with multiple electrodes aligned with the nerve fiber layer can be used to achieve selective activation of axon initial segments rather than passing fibers. This result can be achieved while reducing required stimulus charge density and with only modest increases in the spread of activation in the ganglion cell layer, and is shown to extend to the general case of arbitrary electrode array positioning and arbitrary target volume. Significance. These results elucidate a strategy for more targeted stimulation of retinal ganglion cells with experimentally-relevant multi-electrode geometries and achievable stimulation requirements.
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Affiliation(s)
- Timothy B. Esler
- Department of Biomedical Engineering, The University of Melbourne, Parkville, Victoria, Australia
- * E-mail:
| | - Robert R. Kerr
- Department of Biomedical Engineering, The University of Melbourne, Parkville, Victoria, Australia
- Seer Medical, Melbourne, Victoria, Australia
| | - Bahman Tahayori
- Monash Institute of Medical Engineering, Monash University, Clayton, Victoria, Australia
| | - David B. Grayden
- Department of Biomedical Engineering, The University of Melbourne, Parkville, Victoria, Australia
- Centre for Neural Engineering, The 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, Optometry & Vision Science, The University of Melbourne, Parkville, Victoria, Australia
| | - Anthony N. Burkitt
- Department of Biomedical Engineering, The University of Melbourne, Parkville, Victoria, Australia
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14
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Weiland JD, Walston ST, Humayun MS. Electrical Stimulation of the Retina to Produce Artificial Vision. Annu Rev Vis Sci 2018; 2:273-294. [PMID: 28532361 DOI: 10.1146/annurev-vision-111815-114425] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Retinal prostheses aim to restore vision to blind individuals suffering from retinal diseases such as retinitis pigmentosa and age-related macular degeneration. These devices function by electrically stimulating surviving retinal neurons, whose activation is interpreted by the brain as a visual percept. Many prostheses are currently under development. They are categorized as epiretinal, subretinal, and suprachoroidal prostheses on the basis of the placement of the stimulating microelectrode array. Each can activate ganglion cells through direct or indirect stimulation. The response of retinal neurons to these modes of stimulation are discussed in detail and are placed in context of the visual percept they are likely to evoke. This article further reviews challenges faced by retinal prosthesis and discusses potential solutions to address them.
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Affiliation(s)
- James D Weiland
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California 90007; .,USC Roski Eye Institute, University of Southern California, Los Angeles, California 90033.,Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, California 90033
| | - Steven T Walston
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California 90007;
| | - Mark S Humayun
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California 90007; .,USC Roski Eye Institute, University of Southern California, Los Angeles, California 90033.,Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, California 90033
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15
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An Image-Based miRNA Screen Identifies miRNA-135s As Regulators of CNS Axon Growth and Regeneration by Targeting Krüppel-like Factor 4. J Neurosci 2017; 38:613-630. [PMID: 29196317 DOI: 10.1523/jneurosci.0662-17.2017] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 10/24/2017] [Accepted: 10/29/2017] [Indexed: 01/08/2023] Open
Abstract
During embryonic development, axons extend over long distances to establish functional connections. In contrast, axon regeneration in the adult mammalian CNS is limited in part by a reduced intrinsic capacity for axon growth. Therefore, insight into the intrinsic control of axon growth may provide new avenues for enhancing CNS regeneration. Here, we performed one of the first miRNome-wide functional miRNA screens to identify miRNAs with robust effects on axon growth. High-content screening identified miR-135a and miR-135b as potent stimulators of axon growth and cortical neuron migration in vitro and in vivo in male and female mice. Intriguingly, both of these developmental effects of miR-135s relied in part on silencing of Krüppel-like factor 4 (KLF4), a well known intrinsic inhibitor of axon growth and regeneration. These results prompted us to test the effect of miR-135s on axon regeneration after injury. Our results show that intravitreal application of miR-135s facilitates retinal ganglion cell (RGC) axon regeneration after optic nerve injury in adult mice in part by repressing KLF4. In contrast, depletion of miR-135s further reduced RGC axon regeneration. Together, these data identify a novel neuronal role for miR-135s and the miR-135-KLF4 pathway and highlight the potential of miRNAs as tools for enhancing CNS axon regeneration.SIGNIFICANCE STATEMENT Axon regeneration in the adult mammalian CNS is limited in part by a reduced intrinsic capacity for axon growth. Therefore, insight into the intrinsic control of axon growth may provide new avenues for enhancing regeneration. By performing an miRNome-wide functional screen, our studies identify miR-135s as stimulators of axon growth and neuron migration and show that intravitreal application of these miRNAs facilitates CNS axon regeneration after nerve injury in adult mice. Intriguingly, these developmental and regeneration-promoting effects rely in part on silencing of Krüppel-like factor 4 (KLF4), a well known intrinsic inhibitor of axon regeneration. Our data identify a novel neuronal role for the miR-135-KLF4 pathway and support the idea that miRNAs can be used for enhancing CNS axon regeneration.
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16
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Chang YC, Walston ST, Chow RH, Weiland JD. GCaMP expression in retinal ganglion cells characterized using a low-cost fundus imaging system. J Neural Eng 2017; 14:056018. [PMID: 28930702 DOI: 10.1088/1741-2552/aa7ded] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVE Virus-transduced, intracellular-calcium indicators are effective reporters of neural activity, offering the advantage of cell-specific labeling. Due to the existence of an optimal time window for the expression of calcium indicators, a suitable tool for tracking GECI expression in vivo following transduction is highly desirable. APPROACH We developed a noninvasive imaging approach based on a custom-modified, low-cost fundus viewing system that allowed us to monitor and characterize in vivo bright-field and fluorescence images of the mouse retina. AAV2-CAG-GCaMP6f was injected into a mouse eye. The fundus imaging system was used to measure fluorescence at several time points post injection. At defined time points, we prepared wholemount retina mounted on a transparent multielectrode array and used calcium imaging to evaluate the responsiveness of retinal ganglion cells (RGCs) to external electrical stimulation. MAIN RESULTS The noninvasive fundus imaging system clearly resolves individual (RGCs and axons. RGC fluorescence intensity and the number of observable fluorescent cells show a similar rising trend from week 1 to week 3 after viral injection, indicating a consistent increase of GCaMP6f expression. Analysis of the in vivo fluorescence intensity trend and in vitro neurophysiological responsiveness shows that the slope of intensity versus days post injection can be used to estimate the optimal time for calcium imaging of RGCs in response to external electrical stimulation. SIGNIFICANCE The proposed fundus imaging system enables high-resolution digital fundus imaging in the mouse eye, based on off-the-shelf components. The long-term tracking experiment with in vitro calcium imaging validation demonstrates the system can serve as a powerful tool monitoring the level of genetically-encoded calcium indicator expression, further determining the optimal time window for following experiment.
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Affiliation(s)
- Yao-Chuan Chang
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, United States of America
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17
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Chang YC, Weiland JD. Stimulation Strategies for Selective Activation of Retinal Ganglion Cells. INTERNATIONAL IEEE/EMBS CONFERENCE ON NEURAL ENGINEERING : [PROCEEDINGS]. INTERNATIONAL IEEE EMBS CONFERENCE ON NEURAL ENGINEERING 2017; 2017:345-348. [PMID: 31391873 DOI: 10.1109/ner.2017.8008361] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Retinal prosthetic implants have shown potential to restore partial vision to patients blinded by retinitis pigmentosa or dry age-related macular degeneration, via a camera-driven multielectrode array that electrically stimulates surviving retinal neurons. Commercial epi-retinal prostheses mostly use charge-balanced symmetric cathodic-first biphasic pulses to depolarize retinal ganglion cells (RGCs) and bipolar cells (BCs), resulting in the perception of light in blind patients. However, previous clinical study for patients with Argus II epiretinal implants reported most percepts evoked by single electrode stimulation were elongated and aligned with estimated axon path of retinal ganglion cells, suggesting the activation of axon bundles. In this project, using an established genetically encoded calcium indicator (GECI), we performed in vitro calcium imaging for different stimulation paradigms, focusing primarily on short duration pulse that can avoid axonal stimulation and selective activate targeted RGC soma. The findings support the possibility to manipulate the responses of RGCs through varying the stimulation waveform, thus potentially forming more ideal shape perception with higher spatial resolution in future retinal prosthesis design.
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Affiliation(s)
- Yao-Chuan Chang
- University of Southern California, Los Angeles, CA 90033, USA
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18
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Grosberg LE, Ganesan K, Goetz GA, Madugula SS, Bhaskhar N, Fan V, Li P, Hottowy P, Dabrowski W, Sher A, Litke AM, Mitra S, Chichilnisky EJ. Activation of ganglion cells and axon bundles using epiretinal electrical stimulation. J Neurophysiol 2017; 118:1457-1471. [PMID: 28566464 DOI: 10.1152/jn.00750.2016] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 05/30/2017] [Accepted: 05/30/2017] [Indexed: 12/17/2022] Open
Abstract
Epiretinal prostheses for treating blindness activate axon bundles, causing large, arc-shaped visual percepts that limit the quality of artificial vision. Improving the function of epiretinal prostheses therefore requires understanding and avoiding axon bundle activation. This study introduces a method to detect axon bundle activation on the basis of its electrical signature and uses the method to test whether epiretinal stimulation can directly elicit spikes in individual retinal ganglion cells without activating nearby axon bundles. Combined electrical stimulation and recording from isolated primate retina were performed using a custom multielectrode system (512 electrodes, 10-μm diameter, 60-μm pitch). Axon bundle signals were identified by their bidirectional propagation, speed, and increasing amplitude as a function of stimulation current. The threshold for bundle activation varied across electrodes and retinas, and was in the same range as the threshold for activating retinal ganglion cells near their somas. In the peripheral retina, 45% of electrodes that activated individual ganglion cells (17% of all electrodes) did so without activating bundles. This permitted selective activation of 21% of recorded ganglion cells (7% of expected ganglion cells) over the array. In one recording in the central retina, 75% of electrodes that activated individual ganglion cells (16% of all electrodes) did so without activating bundles. The ability to selectively activate a subset of retinal ganglion cells without axon bundles suggests a possible novel architecture for future epiretinal prostheses.NEW & NOTEWORTHY Large-scale multielectrode recording and stimulation were used to test how selectively retinal ganglion cells can be electrically activated without activating axon bundles. A novel method was developed to identify axon activation on the basis of its unique electrical signature and was used to find that a subset of ganglion cells can be activated at single-cell, single-spike resolution without producing bundle activity in peripheral and central retina. These findings have implications for the development of advanced retinal prostheses.
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Affiliation(s)
- Lauren E Grosberg
- Department of Neurosurgery and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California;
| | - Karthik Ganesan
- Departments of Electrical Engineering and Computer Science, Stanford University, Stanford, California
| | - Georges A Goetz
- Department of Neurosurgery and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California
| | - Sasidhar S Madugula
- Department of Neurosurgery and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California
| | - Nandita Bhaskhar
- Departments of Electrical Engineering and Computer Science, Stanford University, Stanford, California
| | - Victoria Fan
- Department of Neurosurgery and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California
| | - Peter Li
- Systems Neurobiology Laboratories, Salk Institute for Biological Studies, La Jolla, California
| | - Pawel Hottowy
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Krakow, Poland; and
| | - Wladyslaw Dabrowski
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Krakow, Poland; and
| | - Alexander Sher
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, Santa Cruz, California
| | - Alan M Litke
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, Santa Cruz, California
| | - Subhasish Mitra
- Departments of Electrical Engineering and Computer Science, Stanford University, Stanford, California
| | - E J Chichilnisky
- Department of Neurosurgery and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California
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19
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Chang YC, Walston ST, Chow RH, Weiland JD. In vivo characterization of genetic expression of virus-transduced calcium indicators in retinal ganglion cells using a low-cost funduscope. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2017; 2016:1316-1319. [PMID: 28261004 DOI: 10.1109/embc.2016.7590949] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Virus-transduced calcium indicators are effective reporters of neural activity, offering the advantage of cell-specific labeling. To track the level of in vivo expression of genetically encoded calcium indicators (GECIs) in rodent retina, we developed a noninvasive imaging approach based on a custom-modified low-cost and simple fundus system that enabled us to monitor and characterize in vivo bright-field and fluorescence retinal image. The system clearly resolves individual retinal ganglion cells (RGCs) and axons. RGC fluorescence intensity and number of observable fluorescent cells show a consistent rising trend from week 1 to week 3 after viral injection, indicating a uniform increase of GCaMP6f expression. At defined time points, we prepared wholemount retina mounted on a transparent multielectrode array (MEA) and used calcium imaging to identify the optimal time for studying the responsiveness of RGCs to external electrical stimulation. The results show that the fluorescence-endoscopy fundus system is a powerful and widely accessible tool for evaluating in vivo fluorescence reporter expression.
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Affiliation(s)
- Yao-Chuan Chang
- University of Southern California, Los Angeles, ca 90033, USA
| | | | - Robert H Chow
- University of Southern California, Los Angeles, ca 90033, USA
| | - James D Weiland
- University of Southern California, Los Angeles, ca 90033, USA
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20
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Walston ST, Chow RH, Weiland JD. Patch clamp recordings of retinal bipolar cells in response to extracellular electrical stimulation in wholemount 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; 2015:3363-6. [PMID: 26737013 DOI: 10.1109/embc.2015.7319113] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Retinitis pigmentosa is a family of inherited retinal diseases identified by the degeneration of photoreceptors, which leads to blindness. In efforts to restore vision lost to retinitis pigmentosa, retinal prostheses have been developed to generate visual percepts by electrically stimulating the surviving retinal bipolar and ganglion cells. The response of retinal ganglion cells to electrical stimulation has been characterized through direct measurement. However, the response of bipolar cells has only been inferred by measuring retinal ganglion cell activity. This investigation reports on a novel tissue preparation technique facilitating bipolar cell patch clamp recordings in wholemount retina. We find that bipolar cells respond to extracellular electrical stimuli with time-locked voltage spike depolarizations, which are likely mediated by voltage-gated calcium channels.
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21
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Eleftheriou CG, Zimmermann JB, Kjeldsen HD, David-Pur M, Hanein Y, Sernagor E. Carbon nanotube electrodes for retinal implants: A study of structural and functional integration over time. Biomaterials 2016; 112:108-121. [PMID: 27760395 PMCID: PMC5123641 DOI: 10.1016/j.biomaterials.2016.10.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 10/08/2016] [Accepted: 10/11/2016] [Indexed: 12/15/2022]
Abstract
The choice of electrode material is of paramount importance in neural prosthetic devices. Electrodes must be biocompatible yet able to sustain repetitive current injections in a highly corrosive environment. We explored the suitability of carbon nanotube (CNT) electrodes to stimulate retinal ganglion cells (RGCs) in a mouse model of outer retinal degeneration. We investigated morphological changes at the bio-hybrid interface and changes in RGC responses to electrical stimulation following prolonged in vitro coupling to CNT electrodes. We observed gradual remodelling of the inner retina to incorporate CNT assemblies. Electrophysiological recordings demonstrate a progressive increase in coupling between RGCs and the CNT electrodes over three days, characterized by a gradual decrease in stimulation thresholds and increase in cellular recruitment. These results provide novel evidence for time-dependent formation of viable bio-hybrids between CNTs and the retina, demonstrating that CNTs are a promising material for inclusion in retinal prosthetic devices.
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Affiliation(s)
- Cyril G Eleftheriou
- Institute of Neuroscience, Faculty of Medical Sciences, Newcastle University, Framlington Place, Newcastle-upon-Tyne, NE2 4HH, United Kingdom
| | - Jonas B Zimmermann
- Institute of Neuroscience, Faculty of Medical Sciences, Newcastle University, Framlington Place, Newcastle-upon-Tyne, NE2 4HH, United Kingdom
| | - Henrik D Kjeldsen
- Institute of Neuroscience, Faculty of Medical Sciences, Newcastle University, Framlington Place, Newcastle-upon-Tyne, NE2 4HH, United Kingdom
| | - Moshe David-Pur
- School of Electrical Engineering, Tel-Aviv University, Ramat-Aviv, Tel-Aviv, 69978, Israel
| | - Yael Hanein
- School of Electrical Engineering, Tel-Aviv University, Ramat-Aviv, Tel-Aviv, 69978, Israel
| | - Evelyne Sernagor
- Institute of Neuroscience, Faculty of Medical Sciences, Newcastle University, Framlington Place, Newcastle-upon-Tyne, NE2 4HH, United Kingdom.
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22
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Weitz AC, Nanduri D, Behrend MR, Gonzalez-Calle A, Greenberg RJ, Humayun MS, Chow RH, Weiland JD. Improving the spatial resolution of epiretinal implants by increasing stimulus pulse duration. Sci Transl Med 2016; 7:318ra203. [PMID: 26676610 DOI: 10.1126/scitranslmed.aac4877] [Citation(s) in RCA: 128] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Retinal prosthetic implants are the only approved treatment for retinitis pigmentosa, a disease of the eye that causes blindness through gradual degeneration of photoreceptors. An array of microelectrodes triggered by input from a camera stimulates surviving retinal neurons, with each electrode acting as a pixel. Unintended stimulation of retinal ganglion cell axons causes patients to see large oblong shapes of light, rather than focal spots, making it difficult to perceive forms. To address this problem, we performed calcium imaging in isolated retinas and mapped the patterns of cells activated by different electrical stimulation protocols. We found that pulse durations two orders of magnitude longer than those typically used in existing implants stimulated inner retinal neurons while avoiding activation of ganglion cell axons, thus confining retinal responses to the site of the electrode. Multielectrode stimulation with 25-ms pulses can pattern letters on the retina corresponding to a Snellen acuity of 20/312. We validated our findings in a patient with an implanted epiretinal prosthesis by demonstrating that 25-ms pulses evoke focal spots of light.
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Affiliation(s)
- Andrew C Weitz
- Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Devyani Nanduri
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Matthew R Behrend
- Department of Electrical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Alejandra Gonzalez-Calle
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | | | - Mark S Humayun
- Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Robert H Chow
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA. Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
| | - James D Weiland
- Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA.
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Retinal gene delivery by adeno-associated virus (AAV) vectors: Strategies and applications. Eur J Pharm Biopharm 2015; 95:343-52. [DOI: 10.1016/j.ejpb.2015.01.009] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 01/10/2015] [Accepted: 01/12/2015] [Indexed: 11/20/2022]
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24
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Generation of a Homozygous Transgenic Rat Strain Stably Expressing a Calcium Sensor Protein for Direct Examination of Calcium Signaling. Sci Rep 2015; 5:12645. [PMID: 26234466 PMCID: PMC4522653 DOI: 10.1038/srep12645] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 07/03/2015] [Indexed: 12/16/2022] Open
Abstract
In drug discovery, prediction of selectivity and toxicity require the evaluation of cellular calcium homeostasis. The rat is a preferred laboratory animal for pharmacology and toxicology studies, while currently no calcium indicator protein expressing rat model is available. We established a transgenic rat strain stably expressing the GCaMP2 fluorescent calcium sensor by a transposon-based methodology. Zygotes were co-injected with mRNA of transposase and a CAG-GCaMP2 expressing construct, and animals with one transgene copy were pre-selected by measuring fluorescence in blood cells. A homozygous rat strain was generated with high sensor protein expression in the heart, kidney, liver, and blood cells. No pathological alterations were found in these animals, and fluorescence measurements in cardiac tissue slices and primary cultures demonstrated the applicability of this system for studying calcium signaling. We show here that the GCaMP2 expressing rat cardiomyocytes allow the prediction of cardiotoxic drug side-effects, and provide evidence for the role of Na+/Ca2+ exchanger and its beneficial pharmacological modulation in cardiac reperfusion. Our data indicate that drug-induced alterations and pathological processes can be followed by using this rat model, suggesting that transgenic rats expressing a calcium-sensitive protein provide a valuable system for pharmacological and toxicological studies.
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25
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Tanamoto R, Shindo Y, Miki N, Matsumoto Y, Hotta K, Oka K. Electrical stimulation of cultured neurons using a simply patterned indium-tin-oxide (ITO) glass electrode. J Neurosci Methods 2015; 253:272-8. [PMID: 26185873 DOI: 10.1016/j.jneumeth.2015.07.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Revised: 07/03/2015] [Accepted: 07/04/2015] [Indexed: 11/20/2022]
Abstract
BACKGROUND Indium-tin-oxide (ITO) glass electrodes possess the properties of optical transparency and high electrical conductivity, which enables the electrical stimulation of cultured cells to be performed whilst also measuring the responses with fluorescent imaging techniques. However, the quantitative relationship between the intensity of the stimulating current and the cell response is unclear when using conventional methods that employ a separated configuration of counter and stimulation electrodes. NEW METHOD A quantitative electrical current stimulation device without the use of a counter electrode was fabricated. RESULTS Nerve growth factor (NGF)-induced differentiated PC12 cells were cultured on an ITO single glass electrode, and the Ca(2+) response to electrical stimuli was measured using fluorescent Ca(2+) imaging. ITO electrode devices with a width less than 0.1mm were found to evoke a Ca(2+) response in the PC12 cells. Subsequent variation in the length of the device in the range of 2-10mm was found to have little influence on the efficiency of the electric stimulus. We found that the stimulation of the cells was dependent on the electrical current, when greater than 60 μA, rather than on the Joule heat, regardless of the width and length of the conductive area. COMPARISON WITH EXISTING METHOD(S) Because of the cells directly in contact with the electrode, our device enables to stimulate the cells specifically, comparing with previous devices with the counter electrode. CONCLUSIONS The ITO device without the use of a counter electrode is a useful tool for evaluating the quantitative neural excitability of cultured neurons.
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Affiliation(s)
- Ryo Tanamoto
- Department of Bioscience and Informatics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, 223-8522, Japan
| | - Yutaka Shindo
- Department of Bioscience and Informatics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, 223-8522, Japan
| | - Norihisa Miki
- Department of Mechanical Engineering, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, 223-8522, Japan
| | - Yoshinori Matsumoto
- Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, 223-8522, Japan
| | - Kohji Hotta
- Department of Bioscience and Informatics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, 223-8522, Japan
| | - Kotaro Oka
- Department of Bioscience and Informatics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, 223-8522, Japan.
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Bogner B, Boye SL, Min SH, Peterson JJ, Ruan Q, Zhang Z, Reitsamer HA, Hauswirth WW, Boye SE. Capsid Mutated Adeno-Associated Virus Delivered to the Anterior Chamber Results in Efficient Transduction of Trabecular Meshwork in Mouse and Rat. PLoS One 2015; 10:e0128759. [PMID: 26052939 PMCID: PMC4460001 DOI: 10.1371/journal.pone.0128759] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 04/30/2015] [Indexed: 12/19/2022] Open
Abstract
Background Adeno associated virus (AAV) is well known for its ability to deliver transgenes to retina and to mediate improvements in animal models and patients with inherited retinal disease. Although the field is less advanced, there is growing interest in AAV’s ability to target cells of the anterior segment. The purpose of our study was to fully articulate a reliable and reproducible method for injecting the anterior chamber (AC) of mice and rats and to investigate the transduction profiles of AAV2- and AAV8-based capsid mutants containing self-complementary (sc) genomes in the anterior segment of the eye. Methodology/Principle Findings AC injections were performed in C57BL/6 mice and Sprague Dawley rats. The cornea was punctured anterior of the iridocorneal angle. To seal the puncture site and to prevent reflux an air bubble was created in the AC. scAAVs expressing GFP were injected and transduction was evaluated by immunohistochemistry. Both parent serotype and capsid modifications affected expression. scAAV2- based vectors mediated efficient GFP-signal in the corneal endothelium, ciliary non-pigmented epithelium (NPE), iris and chamber angle including trabecular meshwork, with scAAV2(Y444F) and scAAV2(triple) being the most efficient. Conclusions/Significance This is the first study to semi quantitatively evaluate transduction of anterior segment tissues following injection of capsid-mutated AAV vectors. scAAV2- based vectors transduced corneal endothelium, ciliary NPE, iris and trabecular meshwork more effectively than scAAV8-based vectors. Mutagenesis of surface-exposed tyrosine residues greatly enhanced transduction efficiency of scAAV2 in these tissues. The number of Y-F mutations was not directly proportional to transduction efficiency, however, suggesting that proteosomal avoidance alone may not be sufficient. These results are applicable to the development of targeted, gene-based strategies to investigate pathological processes of the anterior segment and may be applied toward the development of gene-based therapies for glaucoma and acquired or inherited corneal anomalies.
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Affiliation(s)
- Barbara Bogner
- Department of Ophthalmology and Optometry, SALK/Paracelsus Medical University, Salzburg, Austria
| | - Sanford L. Boye
- Department of Ophthalmology, University of Florida, Gainesville, United States of America
| | - Seok Hong Min
- Department of Ophthalmology, University of Florida, Gainesville, United States of America
| | - James J. Peterson
- Department of Ophthalmology, University of Florida, Gainesville, United States of America
| | - Qing Ruan
- Department of Ophthalmology, University of Florida, Gainesville, United States of America
| | - Zhonghong Zhang
- Department of Ophthalmology and Optometry, SALK/Paracelsus Medical University, Salzburg, Austria
| | - Herbert A. Reitsamer
- Department of Ophthalmology and Optometry, SALK/Paracelsus Medical University, Salzburg, Austria
| | - William W. Hauswirth
- Department of Ophthalmology, University of Florida, Gainesville, United States of America
| | - Shannon E. Boye
- Department of Ophthalmology, University of Florida, Gainesville, United States of America
- * E-mail:
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Samba R, Herrmann T, Zeck G. PEDOT–CNT coated electrodes stimulate retinal neurons at low voltage amplitudes and low charge densities. J Neural Eng 2015; 12:016014. [DOI: 10.1088/1741-2560/12/1/016014] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Wang B, Petrossians A, Weiland JD. Reduction of edge effect on disk electrodes by optimized current waveform. IEEE Trans Biomed Eng 2014; 61:2254-63. [PMID: 25051544 DOI: 10.1109/tbme.2014.2300860] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Rectangular pulses applied to disk electrodes result in high current density at the edges of the disk, which can lead to electrode corrosion and tissue damage. We explored a method for reducing current density and corrosion, by varying the leading edge of the current pulse. Finite-element modeling and mathematical analysis were used to predict an optimal waveform that reduces current density at the edge while also maintaining short pulse duration. An approximation of the optimized waveform was implemented experimentally and applied to platinum disk electrodes. Surface analysis using energy-dispersive spectroscopy showed significant reduction of corrosion on the periphery of these electrodes after pulsing, compared to those pulsed with the control rectangular waveform.
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Kiral-Kornek FI, OʼSullivan-Greene E, Savage CO, McCarthy C, Grayden DB, Burkitt AN. Improved visual performance in letter perception through edge orientation encoding in a retinal prosthesis simulation. J Neural Eng 2014; 11:066002. [PMID: 25307496 DOI: 10.1088/1741-2560/11/6/066002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Objective. Stimulation strategies for retinal prostheses predominately seek to directly encode image brightness values rather than edge orientations. Recent work suggests that the generation of oriented elliptical phosphenes may be possible by controlling interactions between neighboring electrodes. Based on this, we propose a novel stimulation strategy for prosthetic vision that extracts edge orientation information from the intensity image and encodes it as oriented elliptical phosphenes. We test the hypothesis that encoding edge orientation via oriented elliptical phosphenes leads to better alphabetic letter recognition than standard intensity-based encoding. Approach. We conduct a psychophysical study with simulated phosphene vision with 12 normal-sighted volunteers. The two stimulation strategies were compared with variations of letter size, electrode drop-out and spatial offsets of phosphenes. Main results. Mean letter recognition accuracy was significantly better with the new proposed stimulation strategy (65%) compared to direct grayscale encoding (47%). All examined parameters-stimulus size, phosphene dropout, and location shift-were found to influence the performance, with significant two-way interactions between phosphene dropout and stimulus size as well as between phosphene dropout and phosphene location shift. The analysis delivers a model of perception performance. Significance. Displaying available directional information to an implant user may improve their visual performance. We present a model for designing a stimulation strategy under the constraints of existing retinal prostheses that can be exploited by retinal implant developers to strategically employ oriented phosphenes.
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Affiliation(s)
- F Isabell Kiral-Kornek
- NeuroEngineering Laboratory, Department of Electrical & Electronic Engineering, The University of Melbourne, Australia. Centre for Neural Engineering, The University of Melbourne, Australia. NICTA, c/- Department of Electrical & Electronic Engineering, The University of Melbourne, Australia
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Sargoy A, Barnes S, Brecha NC, Pérez De Sevilla Müller L. Immunohistochemical and calcium imaging methods in wholemount rat retina. J Vis Exp 2014:e51396. [PMID: 25349920 DOI: 10.3791/51396] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
In this paper we describe the tools, reagents, and the practical steps that are needed for: 1) successful preparation of wholemount retinas for immunohistochemistry and, 2) calcium imaging for the study of voltage gated calcium channel (VGCC) mediated calcium signaling in retinal ganglion cells. The calcium imaging method we describe circumvents issues concerning non-specific loading of displaced amacrine cells in the ganglion cell layer.
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Affiliation(s)
- Allison Sargoy
- Department of Neurobiology, University of California, Los Angeles
| | - Steven Barnes
- Department of Neurobiology, University of California, Los Angeles; Veterans Administration Greater Los Angeles Healthcare System; Departments of Physiology & Biophysics and Ophthalmology & Visual Sciences, Dalhousie University
| | - Nicholas C Brecha
- Department of Neurobiology, University of California, Los Angeles; Veterans Administration Greater Los Angeles Healthcare System; Departments of Neurobiology and Medicine, Jules Stein Eye Institute, CURE-Digestive Diseases Research Center, David Geffen School of Medicine, University of California, Los Angeles
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31
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Weitz AC, Behrend MR, Ahuja AK, Christopher P, Wei J, Wuyyuru V, Patel U, Greenberg RJ, Humayun MS, Chow RH, Weiland JD. Interphase gap as a means to reduce electrical stimulation thresholds for epiretinal prostheses. J Neural Eng 2014; 11:016007. [PMID: 24654269 DOI: 10.1088/1741-2560/11/1/016007] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Epiretinal prostheses are designed to restore functional vision to the blind by electrically stimulating surviving retinal neurons. These devices have classically employed symmetric biphasic current pulses in order to maintain a balance of charge. Prior electrophysiological and psychophysical studies in peripheral nerve show that adding an interphase gap (IPG) between the two phases makes stimulation more efficient than pulses with no gap. This led us to investigate the effect of IPG duration on retinal stimulation thresholds. APPROACH We measured retinal ganglion cell (RGC) electrical thresholds in salamander retina and phosphene perceptual thresholds in epiretinal prosthesis patients during stimulation with different IPG lengths. We also built Hodgkin-Huxley-type models of RGCs to further study how IPG affects thresholds. MAIN RESULTS In general, there was a negative exponential correlation between threshold and IPG duration. Durations greater than or equal to ~0.5 ms reduced salamander RGC thresholds by 20-25%. Psychophysical testing in five retinal prosthesis patients indicated that stimulating with IPGs can decrease perceptual thresholds by 10-15%. Results from computational models of RGCs corroborated the observed behavior. SIGNIFICANCE Incorporating interphase gaps can reduce the power consumption of epiretinal prostheses and increase the available dynamic range of phosphene size and brightness.
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Eickenscheidt M, Zeck G. Action potentials in retinal ganglion cells are initiated at the site of maximal curvature of the extracellular potential. J Neural Eng 2014; 11:036006. [DOI: 10.1088/1741-2560/11/3/036006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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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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Loss of Pde6 reduces cell body Ca(2+) transients within photoreceptors. Cell Death Dis 2013; 4:e797. [PMID: 24030149 PMCID: PMC3789190 DOI: 10.1038/cddis.2013.332] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 07/21/2013] [Accepted: 07/29/2013] [Indexed: 11/30/2022]
Abstract
Modulation of Ca2+ within cells is tightly regulated through complex and dynamic interactions between the plasma membrane and internal compartments. In this study, we exploit in vivo imaging strategies based on genetically encoded Ca2+ indicators to define changes in perikaryal Ca2+ concentration of intact photoreceptors. We developed double-transgenic zebrafish larvae expressing GCaMP3 in all cones and tdTomato in long-wavelength cones to test the hypothesis that photoreceptor degeneration induced by mutations in the phosphodiesterase-6 (Pde6) gene is driven by excessive [Ca2+]i levels within the cell body. Arguing against Ca2+ overload in Pde6 mutant photoreceptors, simultaneous analysis of cone photoreceptor morphology and Ca2+ fluxes revealed that degeneration of pde6cw59 mutant cones, which lack the cone-specific cGMP phosphodiesterase, is not associated with sustained increases in perikaryal [Ca2+]i. Analysis of [Ca2+]i in dissociated Pde6βrd1mouse rods shows conservation of this finding across vertebrates. In vivo, transient and Pde6-independent Ca2+ elevations (‘flashes') were detected throughout the inner segment and the synapse. As the mutant cells proceeded to degenerate, these Ca2+ fluxes diminished. This study thus provides insight into Ca2+ dynamics in a common form of inherited blindness and uncovers a dramatic, light-independent modulation of [Ca2+]i that occurs in normal cones.
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Yin L, Geng Y, Osakada F, Sharma R, Cetin AH, Callaway EM, Williams DR, Merigan WH. Imaging light responses of retinal ganglion cells in the living mouse eye. J Neurophysiol 2013; 109:2415-21. [PMID: 23407356 DOI: 10.1152/jn.01043.2012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
This study reports development of a novel method for high-resolution in vivo imaging of the function of individual mouse retinal ganglion cells (RGCs) that overcomes many limitations of available methods for recording RGC physiology. The technique combines insertion of a genetically encoded calcium indicator into RGCs with imaging of calcium responses over many days with FACILE (functional adaptive optics cellular imaging in the living eye). FACILE extends the most common method for RGC physiology, in vitro physiology, by allowing repeated imaging of the function of each cell over many sessions and by avoiding damage to the retina during removal from the eye. This makes it possible to track changes in the response of individual cells during morphological development or degeneration. FACILE also overcomes limitations of existing in vivo imaging methods, providing fine spatial and temporal detail, structure-function comparison, and simultaneous analysis of multiple cells.
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Affiliation(s)
- Lu Yin
- Flaum Eye Institute, University of Rochester, Rochester, NY, USA
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