A spectral element method with adaptive segmentation for accurately simulating extracellular electrical stimulation of neurons

Eiber, Calvin D.; Dokos, Socrates; Lovell, Nigel H.; Suaning, Gregg J.

doi:10.1007/s11517-016-1558-x

Cited by 4 publications

(2 citation statements)

References 40 publications

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“…Based on these anisotropic tissue characteristics, it is expected that the orientation of a neurite in retinal tissue can have a significant effect on its activation. However, a common approximation employed by existing computational models of epiretinal stimulation is that the retinal layers are isotropic [ 11 , 16 , 18 , 24 ]. In order to assess the effect of neurite orientation and its interaction with different multi-electrode configurations, computational models of current flow and axonal activation must be developed that can describe the anisotropic characteristics of key retinal layers.…”

Section: Introductionmentioning

confidence: 99%

Minimizing activation of overlying axons with epiretinal stimulation: The role of fiber orientation and electrode configuration

et al. 2018

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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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Section: Introductionmentioning

confidence: 99%

Minimizing activation of overlying axons with epiretinal stimulation: The role of fiber orientation and electrode configuration

et al. 2018

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show abstract

“…It is expected that, based on these anisotropic tissue characteristics, the orientation of a neurite in retinal tissue can have a significant effect on its activation. However, a common approximation employed by existing computational models of epiretinal stimulation is that the retinal layers are isotropic [11,16,18,23]. In order to assess the effect of neurite orientation, and its interaction with different multi-electrode configurations, computational models of current flow and axonal activation should be developed that can describe the anisotropic characteristics of different retinal layers.…”

Section: Introductionmentioning

confidence: 99%

Minimizing activation of overlying axons with epiretinal stimulation: The role of fiber orientation and electrode configuration

Esler

Kerr

Tahayori

et al. 2018

Preprint

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Objective. Currently, a challenge in electrical stimulation of the retina is to excite only the cells lying directly under the electrode in the ganglion cell layer, while avoiding excitation of the axons that pass over the surface of the retina in the nerve fiber layer. Since these passing fibers may originate from distant regions of the ganglion cell layer. Stimulation of both target retinal ganglion cells and overlying axons results in irregular visual percepts, significantly 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 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 modified version of the standard 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. The dependence of fiber activation on the anisotropic nature of the nerve fiber layer is first established. Via a comprehensive search of key parameters, our model shows that the 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 with only a slight increase in total stimulus current and 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 neural volume. Significance. These results elucidate a strategy for more targeted stimulation of retinal ganglion cells with experimentally-relevant multi-electrode geometries and readily achievable stimulation requirements.

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Computational modelling of nerve stimulation and recording with peripheral visceral neural interfaces

et al. 2021

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Objective. Neuromodulation of visceral nerves is being intensively studied for treating a wide range of conditions, but effective translation requires increasing the efficacy and predictability of neural interface performance. Here we use computational models of rat visceral nerve to predict how neuroanatomical variability could affect both electrical stimulation and recording with an experimental planar neural interface. Approach. We developed a hybrid computational pipeline, Visceral Nerve Ensemble Recording and Stimulation (ViNERS), to couple finite-element modelling of extracellular electrical fields with biophysical simulations of individual axons. Anatomical properties of fascicles and axons in rat pelvic and vagus nerves were measured or obtained from public datasets. To validate ViNERS, we simulated pelvic nerve stimulation and recording with an experimental four-electrode planar array. Main results. Axon diameters measured from pelvic nerve were used to model a population of myelinated and unmyelinated axons and simulate recordings of electrically evoked single-unit field potentials (SUFPs). Across visceral nerve fascicles of increasing size, our simulations predicted an increase in stimulation threshold and a decrease in SUFP amplitude. Simulated threshold changes were dominated by changes in perineurium thickness, which correlates with fascicle diameter. We also demonstrated that ViNERS could simulate recordings of electrically-evoked compound action potentials (ECAPs) that were qualitatively similar to pelvic nerve recording made with the array used for simulation. Significance. We introduce ViNERS as a new open-source computational tool for modelling large-scale stimulation and recording from visceral nerves. ViNERS predicts how neuroanatomical variation in rat pelvic nerve affects stimulation and recording with an experimental planar electrode array. We show ViNERS can simulate ECAPS that capture features of our recordings, but our results suggest the underlying NEURON models need to be further refined and specifically adapted to accurately simulate visceral nerve axons.

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A spectral element method with adaptive segmentation for accurately simulating extracellular electrical stimulation of neurons

Cited by 4 publications

References 40 publications

Minimizing activation of overlying axons with epiretinal stimulation: The role of fiber orientation and electrode configuration

Minimizing activation of overlying axons with epiretinal stimulation: The role of fiber orientation and electrode configuration

Minimizing activation of overlying axons with epiretinal stimulation: The role of fiber orientation and electrode configuration

Computational modelling of nerve stimulation and recording with peripheral visceral neural interfaces

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