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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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2
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Xie Y, Qin P, Guo T, Al Abed A, Lovell NH, Tsai D. Modulating individual axons and axonal populations in the peripheral nerve using transverse intrafascicular multichannel electrodes. J Neural Eng 2023; 20:046032. [PMID: 37536318 DOI: 10.1088/1741-2552/aced20] [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: 02/13/2023] [Accepted: 08/03/2023] [Indexed: 08/05/2023]
Abstract
Objective.A transverse intrafascicular multichannel electrode (TIME) may offer advantages over more conventional cuff electrodes including higher spatial selectivity and reduced stimulation charge requirements. However, the performance of TIME, especially in the context of non-conventional stimulation waveforms, remains relatively unexplored. As part of our overarching goal of investigating stimulation efficacy of TIME, we developed a computational toolkit that automates the creation and usage ofin siliconerve models with TIME setup, which solves nerve responses using cable equations and computes extracellular potentials using finite element method.Approach.We began by implementing a flexible and scalable Python/MATLAB-based toolkit for automatically creating models of nerve stimulation in the hybrid NEURON/COMSOL ecosystems. We then developed a sciatic nerve model containing 14 fascicles with 1,170 myelinated (A-type, 30%) and unmyelinated (C-type, 70%) fibers to study fiber responses over a variety of TIME arrangements (monopolar and hexapolar) and stimulation waveforms (kilohertz stimulation and cathodic ramp modulation).Main results.Our toolkit obviates the conventional need to re-create the same nerve in two disparate modeling environments and automates bi-directional transfer of results. Our population-based simulations suggested that kilohertz stimuli provide selective activation of targeted C fibers near the stimulating electrodes but also tended to activate non-targeted A fibers further away. However, C fiber selectivity can be enhanced by hexapolar TIME arrangements that confined the spatial extent of electrical stimuli. Improved upon prior findings, we devised a high-frequency waveform that incorporates cathodic DC ramp to completely remove undesirable onset responses.Conclusion.Our toolkit allows agile, iterative design cycles involving the nerve and TIME, while minimizing the potential operator errors during complex simulation. The nerve model created by our toolkit allowed us to study and optimize the design of next-generation intrafascicular implants for improved spatial and fiber-type selectivity.
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Affiliation(s)
- Yuyang Xie
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
| | - Peijun Qin
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
| | - Tianruo Guo
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
| | - Amr Al Abed
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, 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
| | - David Tsai
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
- School of Electrical Engineering & Telecommunications, UNSW Sydney, NSW 2052, Australia
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3
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Ly K, Guo T, Tsai D, Muralidharan M, Shivdasani MN, Lovell NH, Dokos S. Simulating the impact of photoreceptor loss and inner retinal network changes on electrical activity of the retina. J Neural Eng 2022; 19. [PMID: 36368033 DOI: 10.1088/1741-2552/aca221] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 11/11/2022] [Indexed: 11/13/2022]
Abstract
Objective.A major reason for poor visual outcomes provided by existing retinal prostheses is the limited knowledge of the impact of photoreceptor loss on retinal remodelling and its subsequent impact on neural responses to electrical stimulation. Computational network models of the neural retina assist in the understanding of normal retinal function but can be also useful for investigating diseased retinal responses to electrical stimulation.Approach.We developed and validated a biophysically detailed discrete neuronal network model of the retina in the software package NEURON. The model includes rod and cone photoreceptors, ON and OFF bipolar cell pathways, amacrine and horizontal cells and finally, ON and OFF retinal ganglion cells with detailed network connectivity and neural intrinsic properties. By accurately controlling the network parameters, we simulated the impact of varying levels of degeneration on retinal electrical function.Main results.Our model was able to reproduce characteristic monophasic and biphasic oscillatory patterns seen in ON and OFF neurons during retinal degeneration (RD). Oscillatory activity occurred at 3 Hz with partial photoreceptor loss and at 6 Hz when all photoreceptor input to the retina was removed. Oscillations were found to gradually weaken, then disappear when synapses and gap junctions were destroyed in the inner retina. Without requiring any changes to intrinsic cellular properties of individual inner retinal neurons, our results suggest that changes in connectivity alone were sufficient to give rise to neural oscillations during photoreceptor degeneration, and significant network connectivity destruction in the inner retina terminated the oscillations.Significance.Our results provide a platform for further understanding physiological retinal changes with progressive photoreceptor and inner RD. Furthermore, our model can be used to guide future stimulation strategies for retinal prostheses to benefit patients at different stages of disease progression, particularly in the early and mid-stages of RD.
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Affiliation(s)
- Keith Ly
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW, 2052, Australia
| | - 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
| | | | - Mohit N Shivdasani
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW, 2052, 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
| | - Socrates Dokos
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW, 2052, Australia
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4
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Caravaca-Rodriguez D, Gaytan SP, Suaning GJ, Barriga-Rivera A. Implications of Neural Plasticity in Retinal Prosthesis. Invest Ophthalmol Vis Sci 2022; 63:11. [PMID: 36251317 DOI: 10.1167/iovs.63.11.11] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Retinal degenerative diseases such as retinitis pigmentosa cause a progressive loss of photoreceptors that eventually prevents the affected person from perceiving visual sensations. The absence of a visual input produces a neural rewiring cascade that propagates along the visual system. This remodeling occurs first within the retina. Then, subsequent neuroplastic changes take place at higher visual centers in the brain, produced by either the abnormal neural encoding of the visual inputs delivered by the diseased retina or as the result of an adaptation to visual deprivation. While retinal implants can activate the surviving retinal neurons by delivering electric current, the unselective activation patterns of the different neural populations that exist in the retinal layers differ substantially from those in physiologic vision. Therefore, artificially induced neural patterns are being delivered to a brain that has already undergone important neural reconnections. Whether or not the modulation of this neural rewiring can improve the performance for retinal prostheses remains a critical question whose answer may be the enabler of improved functional artificial vision and more personalized neurorehabilitation strategies.
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Affiliation(s)
- Daniel Caravaca-Rodriguez
- Department of Applied Physics III, Technical School of Engineering, Universidad de Sevilla, Sevilla, Spain
| | - Susana P Gaytan
- Department of Physiology, Universidad de Sevilla, Sevilla, Spain
| | - Gregg J Suaning
- School of Biomedical Engineering, University of Sydney, Sydney, Australia
| | - Alejandro Barriga-Rivera
- Department of Applied Physics III, Technical School of Engineering, Universidad de Sevilla, Sevilla, Spain.,School of Biomedical Engineering, University of Sydney, Sydney, Australia
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5
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Song X, Qiu S, Shivdasani MN, Zhou F, Liu Z, Ma S, Chai X, Chen Y, Cai X, Guo T, Li L. An in-silico analysis of electrically-evoked responses of midget and parasol retinal ganglion cells in different retinal regions. J Neural Eng 2022; 19. [PMID: 35255486 DOI: 10.1088/1741-2552/ac5b18] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 03/07/2022] [Indexed: 11/12/2022]
Abstract
BACKGROUND Visual outcomes provided by present retinal prostheses that primarily target retinal ganglion cells (RGCs) through epiretinal stimulation remain rudimentary, partly due to the limited knowledge of retinal responses under electrical stimulation. Better understanding of how different retinal regions can be quantitatively controlled with high spatial accuracy, will be beneficial to the design of micro-electrode arrays (MEAs) and stimulation strategies for next-generation wide-view, high-resolution epiretinal implants. METHODS A computational model was developed to assess neural activity at different eccentricities (2 mm and 5 mm) within the human retina. This model included midget and parasol RGCs with anatomically accurate cell distribution and cell-specific morphological information. We then performed in silico investigations of region-specific RGC responses to epiretinal electrical stimulation using varied electrode sizes (5 µm - 210 µm diameter), emulating both commercialized retinal implants and recently-developed prototype devices. RESULTS Our model of epiretinal stimulation predicted RGC population excitation analogous to the complex percepts reported in human subjects. Following this, our simulations suggest that midget and parasol RGCs have characteristic regional differences in excitation under preferred electrode sizes. Relatively central (2 mm) regions demonstrated higher number of excited RGCs but lower overall activated receptive field (RF) areas under the same stimulus amplitudes (two-way ANOVA, p < 0.05). Furthermore, the activated RGC numbers per unit active RF area (number-RF ratio) were significantly higher in central than in peripheral regions, and higher in the midget than in the parasol population under all tested electrode sizes (two-way ANOVA, p < 0.05). Our simulations also suggested that smaller electrodes exhibit a higher range of controllable stimulation parameters to achieve pre-defined performance of RGC excitation. ..
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Affiliation(s)
- Xiaoyu Song
- , Shanghai Jiao Tong University, Dongchuan Road, Shanghai Minhang District No. 800, Shanghai, 200240, CHINA
| | - Shirong Qiu
- Shanghai Jiao Tong University, Dongchuan Road, Shanghai Minhang District No. 800, Shanghai, 200240, CHINA
| | - Mohit N Shivdasani
- Graduate School of Biomedical Engineering, University of New South Wales, Lower Ground, Samuels Building (F25), Kensington, New South Wales, 2052, AUSTRALIA
| | - Feng Zhou
- Shanghai Jiao Tong University, Dongchuan Road, Shanghai Minhang District No. 800, Shanghai, 200240, CHINA
| | - Zhengyang Liu
- Shanghai Jiao Tong University, Dongchuan Road, Shanghai Minhang District No. 800, Shanghai, 200240, CHINA
| | - Saidong Ma
- Shanghai Jiao Tong University, Dongchuan Road, Shanghai Minhang District No. 800, Shanghai, 200240, CHINA
| | - Xinyu Chai
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, Shanghai, 200240, CHINA
| | - Yao Chen
- Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200040, Shanghai, 200240, CHINA
| | - Xuan Cai
- Department of Ophthalmology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, Shanghai, 200233, CHINA
| | - Tianruo Guo
- the University of New South Wales, Lower Ground, Samuels Building (F25), Sydney, 2052, AUSTRALIA
| | - Liming Li
- Shanghai Jiao Tong University, Dongchuan Road, Shanghai Minhang District No. 800, Shanghai, 200240, CHINA
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6
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Song X, Guo T, Shivdasani MN, Dokos S, Lovell NH, Li X, Qiu S, Li T, Zheng S, Li L. Creation of virtual channels in the retina using synchronous and asynchronous stimulation - a modelling study. J Neural Eng 2020; 17. [PMID: 33086210 DOI: 10.1088/1741-2552/abc3a9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Accepted: 10/21/2020] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Implantable retinal prostheses aim to provide artificial vision to those suffering from retinal degenerative diseases by electrically stimulating the remaining retinal neurons using a multi-electrode array. The spatial resolution of these devices can be improved by creation of so-called virtual channels (VCs) that are commonly achieved through synchronized stimulation of multiple electrodes. It is largely unclear though if VCs can be created using asynchronous stimulation, which was the primary aim of this study. APPROACH A computational model of multi-layered retina and epi-retinal dual-electrode stimulation was developed to simulate the neural activity of populations of retinal ganglion cells (RGCs) using the VC strategy under both synchronous and asynchronous stimulation conditions. MAIN RESULTS Our simulation suggests that VCs can be created using asynchronous stimulation. VC performance under both synchronous and asynchronous stimulation conditions can be improved by optimizing stimulation parameters such as current intensity, current ratio (α) between two electrodes, electrode spacing and the stimulation waveform. In particular, two VC performance measures; (1) linear displacement of the centroid of RGC activation, and (2) the RGC activation size consistency as a function of different current ratios α, have comparable performance under asynchronous and synchronous stimulation with appropriately selected stimulation parameters. SIGNIFICANCE Our findings support the possibility of creating VCs in the retina under both synchronous and asynchronous stimulation conditions. The results provide theoretical evidence for future retinal prosthesis designs with higher spatial resolution and power efficiency whilst reducing the number of current sources required to achieve these outcomes.
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Affiliation(s)
- Xiaoyu Song
- , Shanghai Jiao Tong University, Shanghai, 200240, CHINA
| | - Tianruo Guo
- GSBME, UNSW, Sydney, New South Wales, 2052, AUSTRALIA
| | - Mohit N Shivdasani
- Graduate School of Biomedical Engineering, University of New South Wales, Lower Ground, Samuels Building (F25), Kensington, New South Wales, AUSTRALIA
| | - Socrates Dokos
- Graduate School of Biomedical Engineering, The University of New South Wales, Sydney 2052, New South Wales, Sydney, New South Wales, 2052, AUSTRALIA
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW 2052, Sydney, 2052, AUSTRALIA
| | - Xinxin Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, CHINA
| | - Shirong Qiu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, CHINA
| | - Tong Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, CHINA
| | - Shiwei Zheng
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, CHINA
| | - Liming Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, Shanghai, CHINA
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7
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Barriga-Rivera A, Guo T, Hayashida Y, Suaning GJ. Editorial: A Conversation With the Brain: Can We Speak Its Language? Front Neurosci 2020; 14:794. [PMID: 32922253 PMCID: PMC7456930 DOI: 10.3389/fnins.2020.00794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 07/06/2020] [Indexed: 11/17/2022] Open
Affiliation(s)
- Alejandro Barriga-Rivera
- School of Biomedical Engineering, The University of Sydney, Sydney, NSW, Australia
- Department of Applied Physics III, University of Seville, Seville, Spain
- *Correspondence: Alejandro Barriga-Rivera
| | - Tianruo Guo
- Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, NSW, Australia
| | - Yuki Hayashida
- Graduate School of Engineering, Osaka University, Osaka, Japan
- Graduate School of Engineering, Mie University, Mie, Japan
| | - Gregg J. Suaning
- School of Biomedical Engineering, The University of Sydney, Sydney, NSW, Australia
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8
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Li Q, Chen M, Zhang C, Lu T, Min S, Li S. Opposite Roles of NT-3 and BDNF in Synaptic Remodeling of the Inner Ear Induced by Electrical Stimulation. Cell Mol Neurobiol 2020; 41:1665-1682. [PMID: 32770528 DOI: 10.1007/s10571-020-00935-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 08/01/2020] [Indexed: 12/11/2022]
Abstract
With the development of neural prostheses, neural plasticity including synaptic remodeling under electrical stimulation is drawing more and more attention. Indeed, intracochlear electrical stimulation used to restore hearing in deaf can induce the loss of residual hearing and synapses of the inner hair cells (IHCs). However, the mechanism under this process is largely unknown. Considering that the guinea pig is always a suitable and convenient choice for the animal model of cochlea implant (CI), in the present study, normal-hearing guinea pigs were implanted with CIs. Four-hour electrical stimulation with the intensity of 6 dB above electrically evoked compound action potential (ECAP) threshold (which can decrease the quantity of IHC synapses and the excitability of the auditory nerve) resulted in the upregulation of Bdnf (p < 0.0001) and downregulation of Nt-3 (p < 0.05). Intracochlear perfusion of exogenous NT-3 or TrkC/Fc (which blocks NT-3) can, respectively, resist or aggravate the synaptic loss induced by electrical stimulation. In contrast, local delivery of exogenous BDNF or TrkB/Fc (which blocks BDNF) to the cochlea, respectively, exacerbated or protected against the synaptic loss caused by electrical stimulation. Notably, the synaptic changes were only observed in the basal and middle halves of the cochlea. All the findings above suggested that NT-3 and BDNF may play opposite roles in the remodeling of IHC synapses induced by intracochlear electrical stimulation, i.e. NT-3 and BDNF promoted the regeneration and degeneration of IHC synapses, respectively.
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Affiliation(s)
- Qiang Li
- ENT Institute and Department of Otolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, China
| | - Min Chen
- ENT Institute and Department of Otolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, China
| | - Chen Zhang
- ENT Institute and Department of Otolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, China
| | - Tianhao Lu
- ENT Institute and Department of Otolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, China
| | - Shiyao Min
- ENT Institute and Department of Otolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, China
| | - Shufeng Li
- ENT Institute and Department of Otolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China. .,NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, China.
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9
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Muralidharan M, Guo T, Shivdasani MN, Tsai D, Fried S, Li L, Dokos S, Morley JW, Lovell NH. Neural activity of functionally different retinal ganglion cells can be robustly modulated by high-rate electrical pulse trains. J Neural Eng 2020; 17:045013. [DOI: 10.1088/1741-2552/ab9a97] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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10
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Tong W, Meffin H, Garrett DJ, Ibbotson MR. Stimulation Strategies for Improving the Resolution of Retinal Prostheses. Front Neurosci 2020; 14:262. [PMID: 32292328 PMCID: PMC7135883 DOI: 10.3389/fnins.2020.00262] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 03/09/2020] [Indexed: 12/17/2022] Open
Abstract
Electrical stimulation using implantable devices with arrays of stimulating electrodes is an emerging therapy for neurological diseases. The performance of these devices depends greatly on their ability to activate populations of neurons with high spatiotemporal resolution. To study electrical stimulation of populations of neurons, retina serves as a useful model because the neural network is arranged in a planar array that is easy to access. Moreover, retinal prostheses are under development to restore vision by replacing the function of damaged light sensitive photoreceptors, which makes retinal research directly relevant for curing blindness. Here we provide a progress review on stimulation strategies developed in recent years to improve the resolution of electrical stimulation in retinal prostheses. We focus on studies performed with explanted retinas, in which electrophysiological techniques are the most advanced. We summarize achievements in improving the spatial and temporal resolution of electrical stimulation of the retina and methods to selectively stimulate neurons with different visual functions. Future directions for retinal prostheses development are also discussed, which could provide insights for other types of neuromodulatory devices in which high-resolution electrical stimulation is required.
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Affiliation(s)
- Wei Tong
- National Vision Research Institute, Australian College of Optometry, Carlton, VIC, Australia
- Department of Optometry and Vision Sciences, Melbourne School of Health Sciences, The University of Melbourne, Melbourne, VIC, Australia
- School of Physics, The University of Melbourne, Melbourne, VIC, Australia
| | - Hamish Meffin
- National Vision Research Institute, Australian College of Optometry, Carlton, VIC, Australia
- Department of Optometry and Vision Sciences, Melbourne School of Health Sciences, The University of Melbourne, Melbourne, VIC, Australia
- Department of Biomedical Engineering, The University of Melbourne, Melbourne, VIC, Australia
| | - David J. Garrett
- School of Physics, The University of Melbourne, Melbourne, VIC, Australia
| | - Michael R. Ibbotson
- National Vision Research Institute, Australian College of Optometry, Carlton, VIC, Australia
- Department of Optometry and Vision Sciences, Melbourne School of Health Sciences, The University of Melbourne, Melbourne, VIC, Australia
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11
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Li Q, Lu T, Zhang C, Hansen MR, Li S. Electrical stimulation induces synaptic changes in the peripheral auditory system. J Comp Neurol 2019; 528:893-905. [PMID: 31658367 DOI: 10.1002/cne.24802] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 09/24/2019] [Accepted: 10/12/2019] [Indexed: 12/13/2022]
Abstract
Since a rapidly increasing number of neurostimulation devices are used clinically to modulate specific neural functions, the impact of electrical stimulation on targeted neural structure and function has become a key issue. In particular, the specific effect of electrical stimulation via a cochlear implant (CI) on inner hair cell (IHC) synapses remains unclear. Importantly, CI candidacy has recently expanded to include patients with partial hearing loss. Unfortunately, some CI recipients experience progressive hearing loss after activation of electrical stimulation. The mechanism(s) accounting for loss of residual hearing following electrical stimulation is unknown. Here normal-hearing guinea pigs were implanted with customized CIs. Intracochlear electrical stimulation with an intensity equal to or above electrically evoked compound action potential (ECAP) threshold decreased the excitability of auditory nerve. Furthermore, the number of synapses between IHCs and the afferent spiral ganglion neurons (SGNs) also decreased after electrical stimulation with higher intensities. However, no significant change was observed in the packing density and perikaryal area of SGNs as well as the quantity of hair cells. These results carry important implications for use of CIs in patients with residual hearing and for an increasing number of patients treated with other neurostimulation devices. Notably, the results were based on acute electrical stimulation. Considering the complex interaction between CIs and targeted tissues, it is urgent to conduct further research to clarify whether the similar changes could be induced by chronic electrical stimulation.
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Affiliation(s)
- Qiang Li
- Department of Otolaryngology & Head-Neck Surgery, Eye & ENT Hospital of Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, China
| | - Tianhao Lu
- Department of Otolaryngology & Head-Neck Surgery, Eye & ENT Hospital of Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, China
| | - Chen Zhang
- Department of Otolaryngology & Head-Neck Surgery, Eye & ENT Hospital of Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, China
| | - Marlan R Hansen
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, Iowa
| | - Shufeng Li
- Department of Otolaryngology & Head-Neck Surgery, Eye & ENT Hospital of Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, China
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12
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Ryu SB, Fried SI. Comparison of responses of visual cortical neurons in the mouse to intraocular and extraocular electric stimulation of the retina. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2019; 2018:2458-2461. [PMID: 30440905 DOI: 10.1109/embc.2018.8512795] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Retinal implants offered the promise of restoring functional vision to the blind via the delivery of electrical stimulation to the retina. To enhance the efficacy of these devices, stimulation should elicit neural responses that are similar to the responses that occur naturally in the retina as these have the best chance of carrying a robust signal to visual cortex. A corollary of this is that the responses that arise in visual cortical neurons can be used to compare the effectiveness of different stimulation strategies in the retina. Here, we studied how visual cortical neurons in the mouse respond to monophasic cathodal and anodal electric stimulation delivered via a wire electrode positioned on the outer surface of the eye (extraocular) or within the vitreous cavity of the eye (intraocular). Responses of visual cortical neurons were recorded from primary visual cortex on the side contralateral to the stimulatated eye. For both stimulation modalities, response patterns consisted of a brief burst of spikes followed by a 400-500 ms period of inhibition. Both modalities also elicited stronger responses to cathodal stimuli (vs. anodal). The preferential sensitivity to cathodal stimuli is similar to that of epiretinal stimulation (anodal stimuli are more effective with sub-retinal stimulation) suggest the extraocular approach mirrors epiretinal stimulation. Extraocular stimulation also showed some response characteristics that were different from those observed in the retina, e.g., at very strong amplitudes, cathodal and anodal stimulation produced similar responses.
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13
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Flores T, Huang T, Bhuckory M, Ho E, Chen Z, Dalal R, Galambos L, Kamins T, Mathieson K, Palanker D. Honeycomb-shaped electro-neural interface enables cellular-scale pixels in subretinal prosthesis. Sci Rep 2019; 9:10657. [PMID: 31337815 PMCID: PMC6650428 DOI: 10.1038/s41598-019-47082-y] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 07/10/2019] [Indexed: 11/08/2022] Open
Abstract
High-resolution visual prostheses require small, densely packed pixels, but limited penetration depth of the electric field formed by a planar electrode array constrains such miniaturization. We present a novel honeycomb configuration of an electrode array with vertically separated active and return electrodes designed to leverage migration of retinal cells into voids in the subretinal space. Insulating walls surrounding each pixel decouple the field penetration depth from the pixel width by aligning the electric field vertically, enabling a decrease of the pixel size down to cellular dimensions. We demonstrate that inner retinal cells migrate into the 25 μm deep honeycomb wells as narrow as 18 μm, resulting in more than half of these cells residing within the electrode cavities. Immune response to honeycombs is comparable to that with planar arrays. Modeled stimulation threshold current density with honeycombs does not increase substantially with reduced pixel size, unlike quadratic increase with planar arrays. This 3-D electrode configuration may enable functional restoration of central vision with acuity better than 20/100 for millions of patients suffering from age-related macular degeneration.
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Affiliation(s)
- Thomas Flores
- Department of Applied Physics, Stanford University, Stanford, CA, USA.
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA.
| | - Tiffany Huang
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Mohajeet Bhuckory
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
- Department of Ophthalmology, Stanford University, Stanford, CA, USA
| | - Elton Ho
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
- Department of Physics, Stanford University, Stanford, CA, USA
| | - Zhijie Chen
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Roopa Dalal
- Department of Ophthalmology, Stanford University, Stanford, CA, USA
| | - Ludwig Galambos
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Theodore Kamins
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Keith Mathieson
- Institute of Photonics, University of Strathclyde, Glasgow, Scotland, UK
| | - Daniel Palanker
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
- Department of Ophthalmology, Stanford University, Stanford, CA, USA
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14
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Guo T, Tsai D, Yang CY, Al Abed A, Twyford P, Fried SI, Morley JW, Suaning GJ, Dokos S, Lovell NH. Mediating Retinal Ganglion Cell Spike Rates Using High-Frequency Electrical Stimulation. Front Neurosci 2019; 13:413. [PMID: 31114476 PMCID: PMC6503046 DOI: 10.3389/fnins.2019.00413] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 04/11/2019] [Indexed: 12/30/2022] Open
Abstract
Recent retinal studies have directed more attention to sophisticated stimulation strategies based on high-frequency (>1.0 kHz) electrical stimulation (HFS). In these studies, each retinal ganglion cell (RGC) type demonstrated a characteristic stimulus-strength-dependent response to HFS, offering the intriguing possibility of focally targeting retinal neurons to provide useful visual information by retinal prosthetics. Ionic mechanisms are known to affect the responses of electrogenic cells during electrical stimulation. However, how these mechanisms affect RGC responses is not well understood at present, particularly when applying HFS. Here, we investigate this issue via an in silico model of the RGC. We calibrate and validate the model using an in vitro retinal preparation. An RGC model based on accurate biophysics and realistic representation of cell morphology, was used to investigate how RGCs respond to HFS. The model was able to closely replicate the stimulus-strength-dependent suppression of RGC action potentials observed experimentally. Our results suggest that spike inhibition during HFS is due to local membrane hyperpolarization caused by outward membrane currents near the stimulus electrode. In addition, the extent of HFS-induced inhibition can be largely altered by the intrinsic properties of the inward sodium current. Finally, stimulus-strength-dependent suppression can be modulated by a wide range of stimulation frequencies, under generalized electrode placement conditions. In vitro experiments verified the computational modeling data. This modeling and experimental approach can be extended to further our understanding on the effects of novel stimulus strategies by simulating RGC stimulus-response profiles over a wider range of stimulation frequencies and electrode locations than have previously been explored.
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Affiliation(s)
- Tianruo Guo
- Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, NSW, Australia
| | - David Tsai
- Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, NSW, Australia.,Department of Biological Sciences, Columbia University, New York, NY, United States.,Department of Electrical Engineering, Columbia University, New York, NY, United States
| | - Chih Yu Yang
- Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, NSW, Australia
| | - Amr Al Abed
- Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, NSW, Australia
| | - Perry Twyford
- VA Boston Healthcare System, Boston, MA, United States
| | - Shelley I Fried
- VA Boston Healthcare System, Boston, MA, United States.,Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
| | - John W Morley
- School of Medicine, Western Sydney University, Penrith, NSW, Australia
| | - Gregg J Suaning
- Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, NSW, Australia.,School of Biomedical Engineering, The University of Sydney, Sydney, NSW, Australia
| | - Socrates Dokos
- Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, NSW, Australia
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, NSW, Australia
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15
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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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16
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Fellner A, Stiennon I, Rattay F. Analysis of upper threshold mechanisms of spherical neurons during extracellular stimulation. J Neurophysiol 2019; 121:1315-1328. [PMID: 30726157 DOI: 10.1152/jn.00700.2018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Exceeding a certain stimulation strength can prevent the generation of somatic action potentials, as has been demonstrated in vitro with extracellularly stimulated dorsal root ganglion cells as well as retinal ganglion cells. This phenomenon, termed upper threshold, is currently thought to be a consequence of sodium current reversal in strongly depolarized regions. Here we analyze the contribution of membrane kinetics, using spherical model neurons that are stimulated externally with a microelectrode, in more detail. During extracellular pulse application, the electric field depolarizes one part and hyperpolarizes the other part of the cell. Strong transmembrane currents are generated only in the active depolarized region, changing the overall polarization level. The asymmetric membrane voltage distribution caused by the stimulus strongly influences the cell's behavior during and even after the stimulus. Effects on membrane voltage and transmembrane currents during and after the stimulus are shown and discussed in detail. Aside from the sodium current reversal, two more key mechanisms were identified in causing the upper threshold: strong potassium currents and inactivation of sodium channels. The contributions of the mechanisms involved strongly depend on cell properties, stimulus parameters, and other factors such as temperature. The conclusions presented here are based on several retinal ganglion cell models of the Fohlmeister group, a model with original Hodgkin-Huxley membrane, and a pyramidal cell model. NEW & NOTEWORTHY The upper threshold phenomenon in extracellular stimulation is analyzed in detail for spherical cells. Three main mechanisms were identified that prevent the generation of action potentials at high stimulation strengths: 1) strong potassium currents, 2) inactivating sodium ion channels, and 3) sodium current reversal. Ion channel kinetics in retinal ganglion cells, pyramidal cells, and the original Hodgkin-Huxley model were investigated under the influence of an extracellular stimulus.
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Affiliation(s)
- Andreas Fellner
- Institute for Analysis and Scientific Computing, Vienna University of Technology , Vienna , Austria
| | - Isabel Stiennon
- Institute for Analysis and Scientific Computing, Vienna University of Technology , Vienna , Austria
| | - Frank Rattay
- Institute for Analysis and Scientific Computing, Vienna University of Technology , Vienna , Austria
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17
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Barriga-Rivera A, Suaning GJ, Delgado-Garcia JM, Gruart A. Optic nerve and retinal electrostimulation in rats: direct activation of the retinal ganglion cells. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2018; 2018:1226-1229. [PMID: 30440611 DOI: 10.1109/embc.2018.8512517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Visual prosthesis is competing with biological approaches to restore vision to the blind. Understanding and developing the ability to replicate the neural code of the retina are key factors that can bring bionic vision significant advantage. Here, electrically evoked potentials were recorded in anesthetized rats from the dorsal surface of the superior colliculus. Electrical stimuli of different amplitudes were delivered at the retina and the optic nerve. An evoked potential appeared in both cases within the first 5 ms post-stimulus suggesting that this component of the response was initiated by direct activation of the retinal ganglion cells. However, in the case of retinal neurostimulation, a second evoked potential occurred $9.0 \pm 3.4$ ms after the stimulus delivery. Because this component was not present in the case of optic nerve electrostimulation, it is expected to be originated by the activation of other cells in the retinal network.
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18
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Spike-Conducting Integrate-and-Fire Model. eNeuro 2018; 5:eN-TNC-0112-18. [PMID: 30225348 PMCID: PMC6140110 DOI: 10.1523/eneuro.0112-18.2018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 08/13/2018] [Accepted: 08/14/2018] [Indexed: 11/29/2022] Open
Abstract
Modeling is a useful tool for investigating various biophysical characteristics of neurons. Recent simulation studies of propagating action potentials (spike conduction) along axons include the investigation of neuronal activity evoked by electrical stimulation from implantable prosthetic devices. In contrast to point-neuron simulations, where a large variety of models are readily available, Hodgkin–Huxley-type conductance-based models have been almost the only option for simulating axonal spike conduction, as simpler models cannot faithfully replicate the waveforms of propagating spikes. Since the amount of available physiological data, especially in humans, is usually limited, calibration, and justification of the large number of parameters of a complex model is generally difficult. In addition, not all simulation studies of axons require detailed descriptions of nonlinear ionic dynamics. In this study, we construct a simple model of spike generation and conduction based on the exponential integrate-and-fire model, which can simulate the rapid growth of the membrane potential at spike initiation. In terms of the number of parameters and equations, this model is much more compact than conventional models, but can still reliably simulate spike conduction along myelinated and unmyelinated axons that are stimulated intracellularly or extracellularly. Our simulations of auditory nerve fibers with this new model suggest that, because of the difference in intrinsic membrane properties, the axonal spike conduction of high-frequency nerve fibers is faster than that of low-frequency fibers. The simple model developed in this study can serve as a computationally efficient alternative to more complex models for future studies, including simulations of neuroprosthetic devices.
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19
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Bareket L, Barriga-Rivera A, Zapf MP, Lovell NH, Suaning GJ. Progress in artificial vision through suprachoroidal retinal implants. J Neural Eng 2018; 14:045002. [PMID: 28541930 DOI: 10.1088/1741-2552/aa6cbb] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Retinal implants have proven their ability to restore visual sensation to people with degenerative retinopathy, characterized by photoreceptor cell death and the retina's inability to sense light. Retinal bionics operate by electrically stimulating the surviving neurons in the retina, thus triggering the transfer of visual sensory information to the brain. Suprachoroidal implants were first investigated in Australia in the 1950s. In this approach, the neuromodulation hardware is positioned between the sclera and the choroid, thus providing significant surgical and safety benefits for patients, with the potential to maintain residual vision combined with the artificial input from the device. Here we review the latest advances and state of the art devices for suprachoroidal prostheses, highlight future technologies and discuss challenges and perspectives towards improved rehabilitation of vision.
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Affiliation(s)
- Lilach Bareket
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia
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20
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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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21
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Barriga-Rivera A, Suaning GJ. Visual prostheses, optogenetics, stem cell and gene therapies: splitting the cake. Neural Regen Res 2018; 13:805-806. [PMID: 29863005 PMCID: PMC5998616 DOI: 10.4103/1673-5374.232469] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Affiliation(s)
- Alejandro Barriga-Rivera
- Division of Neuroscience, University Pablo de Olavide, Sevilla, Spain; Faculty of Engineering and Information Technologies, The University of Sydney, Sydney, Australia
| | - Gregg J Suaning
- Faculty of Engineering and Information Technologies, The University of Sydney, Sydney, Australia
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22
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23
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Meng K, Fellner A, Rattay F, Ghezzi D, Meffin H, Ibbotson MR, Kameneva T. Upper stimulation threshold for retinal ganglion cell activation. J Neural Eng 2018; 15:046012. [PMID: 29616983 DOI: 10.1088/1741-2552/aabb7d] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE The existence of an upper threshold in electrically stimulated retinal ganglion cells (RGCs) is of interest because of its relevance to the development of visual prosthetic devices, which are designed to restore partial sight to blind patients. The upper threshold is defined as the stimulation level above which no action potentials (direct spikes) can be elicited in electrically stimulated retina. APPROACH We collected and analyzed in vitro recordings from rat RGCs in response to extracellular biphasic (anodic-cathodic) pulse stimulation of varying amplitudes and pulse durations. Such responses were also simulated using a multicompartment model. MAIN RESULTS We identified the individual cell variability in response to stimulation and the phenomenon known as upper threshold in all but one of the recorded cells (n = 20/21). We found that the latencies of spike responses relative to stimulus amplitude had a characteristic U-shape. In silico, we showed that the upper threshold phenomenon was observed only in the soma. For all tested biphasic pulse durations, electrode positions, and pulse amplitudes above lower threshold, a propagating action potential was observed in the distal axon. For amplitudes above the somatic upper threshold, the axonal action potential back-propagated in the direction of the soma, but the soma's low level of hyperpolarization prevented action potential generation in the soma itself. SIGNIFICANCE An upper threshold observed in the soma does not prevent spike conductance in the axon.
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Affiliation(s)
- Kevin Meng
- National Vision Research Institute, Australian College of Optometry, Australia. Department of Biomedical Engineering, The University of Melbourne, Australia
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24
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Guo T, Yang CY, Tsai D, Muralidharan M, Suaning GJ, Morley JW, Dokos S, Lovell NH. Closed-Loop Efficient Searching of Optimal Electrical Stimulation Parameters for Preferential Excitation of Retinal Ganglion Cells. Front Neurosci 2018; 12:168. [PMID: 29615857 PMCID: PMC5867314 DOI: 10.3389/fnins.2018.00168] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 03/01/2018] [Indexed: 12/20/2022] Open
Abstract
The ability for visual prostheses to preferentially activate functionally-distinct retinal ganglion cells (RGCs) is important for improving visual perception. This study investigates the use of high frequency stimulation (HFS) to elicit RGC activation, using a closed-loop algorithm to search for optimal stimulation parameters for preferential ON and OFF RGC activation, resembling natural physiological neural encoding in response to visual stimuli. We evaluated the performance of a wide range of electrical stimulation amplitudes and frequencies on RGC responses in vitro using murine retinal preparations. It was possible to preferentially excite either ON or OFF RGCs by adjusting amplitudes and frequencies in HFS. ON RGCs can be preferentially activated at relatively higher stimulation amplitudes (>150 μA) and frequencies (2-6.25 kHz) while OFF RGCs are activated by lower stimulation amplitudes (40-90 μA) across all tested frequencies (1-6.25 kHz). These stimuli also showed great promise in eliciting RGC responses that parallel natural RGC encoding: ON RGCs exhibited an increase in spiking activity during electrical stimulation while OFF RGCs exhibited decreased spiking activity, given the same stimulation amplitude. In conjunction with the in vitro studies, in silico simulations indicated that optimal HFS parameters could be rapidly identified in practice, whilst sampling spiking activity of relevant neuronal subtypes. This closed-loop approach represents a step forward in modulating stimulation parameters to achieve appropriate neural encoding in retinal prostheses, advancing control over RGC subtypes activated by electrical stimulation.
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Affiliation(s)
- Tianruo Guo
- Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, NSW, Australia
| | - Chih Yu Yang
- Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, NSW, Australia
| | - David Tsai
- Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, NSW, Australia.,Biological Sciences, Columbia University, New York, NY, United States.,Electrical Engineering, Columbia University, New York, NY, United States
| | | | - Gregg J Suaning
- School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, Sydney, NSW, Australia
| | - John W Morley
- School of Medicine, Western Sydney University, Penrith, NSW, Australia
| | - Socrates Dokos
- Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, NSW, Australia
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, NSW, Australia
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25
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Barriga-Rivera A, Tatarinoff V, Lovell NH, Morley JW, Suaning GJ. Long-term anesthetic protocol in rats: feasibility in electrophysiology studies in visual prosthesis. Vet Ophthalmol 2017; 21:290-297. [PMID: 29148158 DOI: 10.1111/vop.12507] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Electrical stimulation of excitable cells provides therapeutic benefits for a variety of medical conditions, including restoration of partial vision to those blinded via some types of retinal degeneration. To improve visual percepts elicited by the current technology, researchers are conducting acute electrophysiology experiments, mainly in cats. However, the rat can provide a model of a range of retinal diseases and possesses a sufficiently large eye to be used in this field. This article presents a long-term anesthetic protocol to enable electrophysiology experiments to further the development of visual prostheses. Six Long-Evans rats (aged between 14 and 16 weeks) were included in this study. Surgical anesthesia was maintained for more than 15 h by combining constant intravenous infusion of ketamine (24.0-34.5 mg/kg/h), xylazine (0.9-1.2 mg/kg/h), and inhaled isoflurane in oxygen (<0.5%). Overall heart rate, respiratory rate, and body temperature remained between 187-233 beats/min, 45-58 breaths/min, and 36-38 °C, respectively. Neural responses to 200-ms light pulses were recorded from the superior colliculus using a 32-channel neural probe at the beginning and before termination of the experiment. Robust responses were recorded from distinct functional types of retinal pathways. In addition, a platinum electrode was implanted in the retrobulbar space. The retina was electrically stimulated, and the activation threshold was determined to be 5.24 ± 0.24 μC/cm2 . This protocol may be used not only in the field of visual prosthesis research, but in other research areas requiring longer term acute experiments.
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Affiliation(s)
- Alejandro Barriga-Rivera
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW, 2052, Australia.,Division of Neuroscience, University Pablo de Olavide, Sevilla, 41013, Spain
| | - Veronica Tatarinoff
- Sydney Imaging Core Research Facility, The University of Sydney, NSW, 2006, Australia
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW, 2052, Australia
| | - John W Morley
- School of Medicine, The University of Western Sydney, Sydney, NSW, Australia.,School of Medical Science, UNSW, Sydney, NSW, 2052, Australia
| | - Gregg J Suaning
- Sydney Medical School, The University of Sydney, NSW, 2006, Australia.,Faculty of Engineering and Information Technologies, The University of Sydney, NSW, 2006, Australia
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26
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Barriga-Rivera A, Bareket L, Goding J, Aregueta-Robles UA, Suaning GJ. Visual Prosthesis: Interfacing Stimulating Electrodes with Retinal Neurons to Restore Vision. Front Neurosci 2017; 11:620. [PMID: 29184478 PMCID: PMC5694472 DOI: 10.3389/fnins.2017.00620] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 10/23/2017] [Indexed: 01/06/2023] Open
Abstract
The bypassing of degenerated photoreceptors using retinal neurostimulators is helping the blind to recover functional vision. Researchers are investigating new ways to improve visual percepts elicited by these means as the vision produced by these early devices remain rudimentary. However, several factors are hampering the progression of bionic technologies: the charge injection limits of metallic electrodes, the mechanical mismatch between excitable tissue and the stimulating elements, neural and electric crosstalk, the physical size of the implanted devices, and the inability to selectively activate different types of retinal neurons. Electrochemical and mechanical limitations are being addressed by the application of electromaterials such as conducting polymers, carbon nanotubes and nanocrystalline diamonds, among other biomaterials, to electrical neuromodulation. In addition, the use of synthetic hydrogels and cell-laden biomaterials is promising better interfaces, as it opens a door to establishing synaptic connections between the electrode material and the excitable cells. Finally, new electrostimulation approaches relying on the use of high-frequency stimulation and field overlapping techniques are being developed to better replicate the neural code of the retina. All these elements combined will bring bionic vision beyond its present state and into the realm of a viable, mainstream therapy for vision loss.
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Affiliation(s)
- Alejandro Barriga-Rivera
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW, Australia
- Faculty of Engineering and Information Technologies, University of Sydney, Sydney, NSW, Australia
- Division of Neuroscience, University Pablo de Olavide, Sevilla, Spain
| | - Lilach Bareket
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW, Australia
- Faculty of Engineering and Information Technologies, University of Sydney, Sydney, NSW, Australia
| | - Josef Goding
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | | | - Gregg J. Suaning
- Faculty of Engineering and Information Technologies, University of Sydney, Sydney, NSW, Australia
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27
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Barriga-Rivera A, Morley JW, Lovell NH, Suaning GJ. Retinal electrostimulation in rats: Activation thresholds from superior colliculus and visual cortex recordings. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2017; 2017:1166-1169. [PMID: 29060082 DOI: 10.1109/embc.2017.8037037] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Retinal neuromodulation is an emerging therapeutic approach to restore functional vision to those suffering retinal photoreceptor degeneration. The retina encodes visual information and transmits it to the brain. Replicating this retinal code through electrical stimulation is essential to improving the performance of visual prostheses. In doing so, the first step relies on precise neural recordings from visual centers that allow studying the response of these neurons to electrical stimulation of the retina. This paper demonstrates the feasibility of a rat model to conduct highly reliable electrophysiological studies in the field of retinal neuromodulation. A disc electrode, implanted in the retrobulbar space was used to stimulate the retina of Long-Evans rats. Buzsaki multi-electro arrays were inserted in the superior colliculus (SC) to record electrical activity propagated from the retinal ganglion cells (RGCs). Activation thresholds calculated from local field potentials (visual cortex) and from neural spikes (SC) were contrasted. Both values were comparable to those in humans and in other animal models, and were slightly higher when estimated from SC recordings. However, differences were not statistically significant.
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