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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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Wang HZ, Wong YT. A novel simulation paradigm utilising MRI-derived phosphene maps for cortical prosthetic vision. J Neural Eng 2023; 20:046027. [PMID: 37531948 PMCID: PMC10594539 DOI: 10.1088/1741-2552/aceca2] [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: 11/17/2022] [Revised: 07/13/2023] [Accepted: 08/01/2023] [Indexed: 08/04/2023]
Abstract
Objective.We developed a realistic simulation paradigm for cortical prosthetic vision and investigated whether we can improve visual performance using a novel clustering algorithm.Approach.Cortical visual prostheses have been developed to restore sight by stimulating the visual cortex. To investigate the visual experience, previous studies have used uniform phosphene maps, which may not accurately capture generated phosphene map distributions of implant recipients. The current simulation paradigm was based on the Human Connectome Project retinotopy dataset and the placement of implants on the cortices from magnetic resonance imaging scans. Five unique retinotopic maps were derived using this method. To improve performance on these retinotopic maps, we enabled head scanning and a density-based clustering algorithm was then used to relocate centroids of visual stimuli. The impact of these improvements on visual detection performance was tested. Using spatially evenly distributed maps as a control, we recruited ten subjects and evaluated their performance across five sessions on the Berkeley Rudimentary Visual Acuity test and the object recognition task.Main results.Performance on control maps is significantly better than on retinotopic maps in both tasks. Both head scanning and the clustering algorithm showed the potential of improving visual ability across multiple sessions in the object recognition task.Significance.The current paradigm is the first that simulates the experience of cortical prosthetic vision based on brain scans and implant placement, which captures the spatial distribution of phosphenes more realistically. Utilisation of evenly distributed maps may overestimate the performance that visual prosthetics can restore. This simulation paradigm could be used in clinical practice when making plans for where best to implant cortical visual prostheses.
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Affiliation(s)
- Haozhe Zac Wang
- Department of Electrical and Computer Systems Engineering, Monash University, Melbourne, Australia
| | - Yan Tat Wong
- Department of Electrical and Computer Systems Engineering, Monash University, Melbourne, Australia
- Department of Physiology, Monash University, Melbourne, Australia
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Zha M, Muralidharan M, Ly K, Guo T, Von Wegner F, Shabani H, Hosseinzadeh Z, Lovell NH, Rathbun DL, Shivdasani MN. Probing the Contribution of Vertical Processing Layers of the Retina to White-Noise Electrical Stimulation Responses. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-4. [PMID: 38083111 DOI: 10.1109/embc40787.2023.10340816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Optimal stimulus parameters for epiretinal prostheses have been investigated by analyzing retinal ganglion cell (RGC) spiking responses to white-noise electrical stimulation, through a spike-triggered average (STA) analysis technique. However, it is currently unknown as to activation of which retinal cells contribute to features of the STA. We conducted whole-cell patch clamping recordings in ON and OFF RGCs in response to white-noise epiretinal electrical stimulation by using different inhibitors of synaptic transmission in a healthy retina. An mGluR6 agonist, L-AP4, was firstly used to selectively block the output of photoreceptors (PRs) to ON bipolar cells (BCs). We subsequently fully blocked all synaptic inputs to RGCs using a combination of pharmacological agents. Our data shows that PRs dominate the ability of ON RGCs to integrate electrical pulses and form a unique STA shape, while BCs do not contribute in any way. In addition, our results demonstrate that the ability of OFF RGCs to integrate pulses is consistently impaired after blocking the PR to ON BC pathway. We hypothesise that the mechanisms underlying this co-effect are related to the narrow field AII amacrine cells connecting ON and OFF pathways.Clinical Relevance-Recent retinal studies recorded mirror-inverted STAs in ON and OFF retinal pathways, thus raising the possibility of designing a stimulation approach that can differentially activate ON and OFF pathways with electrical stimulation. However, the detailed contribution of three major retinal cell layers in forming characteristic STAs is still unclear. It is of great clinical relevance to investigate the isolated contribution of PRs to the electrically driven STA since PRs progressively degenerate in the course of retinal disease.
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Wu KY, Mina M, Sahyoun JY, Kalevar A, Tran SD. Retinal Prostheses: Engineering and Clinical Perspectives for Vision Restoration. SENSORS (BASEL, SWITZERLAND) 2023; 23:5782. [PMID: 37447632 PMCID: PMC10347280 DOI: 10.3390/s23135782] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 06/04/2023] [Accepted: 06/19/2023] [Indexed: 07/15/2023]
Abstract
A retinal prosthesis, also known as a bionic eye, is a device that can be implanted to partially restore vision in patients with retinal diseases that have resulted in the loss of photoreceptors (e.g., age-related macular degeneration and retinitis pigmentosa). Recently, there have been major breakthroughs in retinal prosthesis technology, with the creation of numerous types of implants, including epiretinal, subretinal, and suprachoroidal sensors. These devices can stimulate the remaining cells in the retina with electric signals to create a visual sensation. A literature review of the pre-clinical and clinical studies published between 2017 and 2023 is conducted. This narrative review delves into the retinal anatomy, physiology, pathology, and principles underlying electronic retinal prostheses. Engineering aspects are explored, including electrode-retina alignment, electrode size and material, charge density, resolution limits, spatial selectivity, and bidirectional closed-loop systems. This article also discusses clinical aspects, focusing on safety, adverse events, visual function, outcomes, and the importance of rehabilitation programs. Moreover, there is ongoing debate over whether implantable retinal devices still offer a promising approach for the treatment of retinal diseases, considering the recent emergence of cell-based and gene-based therapies as well as optogenetics. This review compares retinal prostheses with these alternative therapies, providing a balanced perspective on their advantages and limitations. The recent advancements in retinal prosthesis technology are also outlined, emphasizing progress in engineering and the outlook of retinal prostheses. While acknowledging the challenges and complexities of the technology, this article highlights the significant potential of retinal prostheses for vision restoration in individuals with retinal diseases and calls for continued research and development to refine and enhance their performance, ultimately improving patient outcomes and quality of life.
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Affiliation(s)
- Kevin Y. Wu
- Department of Surgery, Division of Ophthalmology, University of Sherbrooke, Sherbrooke, QC J1G 2E8, Canada; (K.Y.W.)
| | - Mina Mina
- Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Jean-Yves Sahyoun
- Faculty of Medicine, University of Montreal, Montreal, QC H3T 1J4, Canada
| | - Ananda Kalevar
- Department of Surgery, Division of Ophthalmology, University of Sherbrooke, Sherbrooke, QC J1G 2E8, Canada; (K.Y.W.)
| | - Simon D. Tran
- Faculty of Dental Medicine and Oral Health Sciences, McGill University, Montreal, QC H3A 1G1, Canada
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Guo T, Chang YC, Li L, Dokos S, Li L. Editorial: Advances in bioelectronics and stimulation strategies for next generation neuroprosthetics. Front Neurosci 2023; 16:1116900. [PMID: 36704005 PMCID: PMC9872720 DOI: 10.3389/fnins.2022.1116900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 12/13/2022] [Indexed: 01/11/2023] Open
Affiliation(s)
- Tianruo Guo
- Graduate School of Biomedical Engineering, The University of New South Wales Sydney, Sydney, NSW, Australia
| | - Yao-chuan Chang
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, Manhasset, NY, United States,Medtronic PLC, Minneapolis, MN, United States
| | - Luming Li
- National Engineering Research Center of Neuromodulation, School of Aerospace Engineering, Tsinghua University, Beijing, China,Precision Medicine and Healthcare Research Center, Tsinghua-Berkeley Shenzhen Institute, Tsinghua University, Shenzhen, China,IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing, China
| | - Socrates Dokos
- Graduate School of Biomedical Engineering, The University of New South Wales Sydney, Sydney, NSW, Australia
| | - Liming Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China,*Correspondence: Liming Li ✉
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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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Lu Z, Zhou M, Guo T, Liang J, Wu W, Gao Q, Li L, Li H, Chai X. An in-silico analysis of retinal electric field distribution induced by different electrode design of trans-corneal electrical stimulation. J Neural Eng 2022; 19. [PMID: 36044887 DOI: 10.1088/1741-2552/ac8e32] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 08/31/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Trans-corneal electrical stimulation (TcES) produces therapeutic effects on many ophthalmic diseases non-invasively. Existing clinical TcES devices use largely variable design of electrode distribution and stimulation parameters. Better understanding of how electrode configuration paradigms and stimulation parameters influence the electric field distribution on the retina, will be beneficial to the design of next-generation TcES devices. APPROACH In this study, we constructed a realistic finite element human head model with fine eyeball structure. Commonly used DTL-Plus and ERG-Jet electrodes were simulated. We then conducted in silico investigations of retina observation surface (ROS) electric field distributions induced by different return electrode configuration paradigms and different stimulus intensities. MAIN RESULTS Our results suggested that the ROS electric field distribution could be modulated by re-designing TcES electrode settings and stimulus parameters. Under far return location (FRL) paradigms, either DTL-Plus or ERG-Jet approach could induce almost identical ROS electric field distribution regardless where the far return was located. However, compared with the ERG-Jet mode, DTL-Plus stimulation induced stronger nasal lateralization. In contrast, ERG-Jet stimulation induced relatively stronger temporal lateralization. The ROS lateralization can be further tweaked by changing the DTL-Plus electrode length. SIGNIFICANCE These results may contribute to the understanding of the characteristics of DTL-Plus and ERG-Jet electrodes based electric field distribution on the retina, providing practical implications for the therapeutic application of TcES.
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Affiliation(s)
- Zhuofan Lu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Address: 800 Dongchuan Road, Minhang District, Shanghai, Shanghai, 200240, CHINA
| | - Meixuan Zhou
- Shanghai Jiao Tong University, Shanghai 200240, Shanghai, 200240, CHINA
| | - Tianruo Guo
- GSBME, University of New South Wales, Graduate School of Biomedical Engineering, University of New South Wales, NSW 2052, Sydney, Australia, Sydney, New South Wales, 2052, AUSTRALIA
| | - Junling Liang
- Shanghai Jiao Tong University, Address: 800 Dongchuan Road, Minhang District, Shanghai Shanghai, CN 200240, Shanghai, 200240, CHINA
| | - Weilei Wu
- Shanghai Jiao Tong University, School of Biomedical Engineering Shanghai Jiao Tong University , Shanghai Jiao Tong University, 800 Dongchuan Road, Minhang District, Shanghai Shanghai, CN 200240, Shanghai, 200240, CHINA
| | - Qi Gao
- Shanghai Jiao Tong University, Address: 800 Dongchuan Road, Minhang District, Shanghai, Shanghai, 200240, CHINA
| | - Liming Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, Shanghai, 200240, CHINA
| | - Heng Li
- Shanghai Jiao Tong University, Address: 800 Dongchuan Road, Minhang District, Shanghai Shanghai, CN 200240, Shanghai, 200240, CHINA
| | - Xinyu Chai
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, Shanghai, 200240, CHINA
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