Effects of different three-dimensional electrodes on epiretinal electrical stimulation by modeling analysis

Cao, Xun; Sui, Xiaohong; Lyu, Qing; Li, Liming; Chai, Xinyu

doi:10.1186/s12984-015-0065-x

Cited by 26 publications

(27 citation statements)

References 38 publications

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“…Irregular visual percept shapes are commonly described by recipients of epiretinal implants due to stimulation of axons of passage [13,15,20,21]. This effect has been confirmed experimentally and in simulations, and results in a reduction in the spatial selectivity of epiretinal stimulation [11,[15][16][17][20][21][22].…”

Section: Introductionmentioning

confidence: 63%

“…We can first calculate extracellular potential in the region of interest using Equations (10) and then sample it along the desired axon trajectory. This sampled extracellular potential can then be substituted into Equations (16) to yield the membrane potential along the axon.…”

Section: F Generalisation Of Neurite Equationsmentioning

confidence: 99%

“…7 shows that by recruiting more stimulating electrodes the induced area activated becomes greater, it should be noted that this will not necessarily reduce perceived resolution. Previously, recipients of epiretinal implants have reported elongated and line-like phosphenes, thought to be caused by stimulation of passing axons in the NFL that originate from distant regions of the GCL [1,[11][12][13][14][15][16][17][18][19]. Hence, despite an increase in the region of activation in the GCL when using a four-electrode stimulation strategy, the overall resolution is expected to increase due to the elimination of activation of the NFL.…”

Section: B Choosing a Stimulation Strategymentioning

confidence: 99%

“…Although progress to date is highly encouraging, many aspects of the performance of retinal prostheses remain limited, hinging on the ability of these devices to target either specific retinal cell types [9,10] or more precise retinal volumes [1,3,11]. In the case of epiretinal stimulation, a factor limiting performance is the inability of electrical stimulation to preferentially activate target neuronal structures in the ganglion cell layer (GCL) while avoiding activation of overlying axons in the nerve fiber layer (NFL) [1,[11][12][13][14][15][16][17][18][19], illustrated in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

“…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%

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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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