Model - Koppenwallner et al. - Short pulse epiretinal stimulation allows focal activation of retinal ganglion cells
Creators
- 1.
TU Wien
Description
Multi-compartment model associated with Koppenwallner et al. - Short pulse epiretinal stimulation allows focal activation of retinal ganglion cells
Model to simulate neuronal responses to electrical stimulation including simple plot function. The model is the basis for modeling figures 5 & 6 in Koppenwallner et al. (10.1109/TNSRE.2025.3529940). Functionality includes running a specified model RGC and plotting spiking output (e.g., membrane voltage over time) but does not perform threshold searching or other, more complex, analysis.
Context and methodology
- Models of mouse retinal ganglion cells (RGCs) based on 3d tracings of reconstructed cells. Reconstructed cells are based on intracellular Neurobiotin fills, fixation, immunohistochemistry followed by condocal imaging and tracing.
- Electrical stimulation can be applied to test the effect of 10-μs-long biphasic pulses on RGC activation threshold.
Technical details
- Model has been tested in Python 3.13.5 with NEURON (https://neuron.yale.edu/neuron/)
- .mod files in the nrn folder must be compiled prior to run the model using NEURON's mknrndll
- Parameter Stim['somaAxis'] is used to create the main soma axis either along the x, y or z dimension to probe the effect of soatic polarization (Fig. 5 in the paper)
- Parameter Stim['stimPos'] is used to easily position the stimulation electrode either at the soma, the axon or a user-defined position (flex)
- Electrophysiologcial parameters of model RGCs can be modified in rgcTemplate.py
- If help is needed feel free to reach out to Paul Werginz
Data is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0), software is licensed under a MIT License.
Abstract
Epiretinal implants suffer from a lack of spatial resolution, which is greatly influenced by the undesired co-activation of distal cells with their axons passing close to targeted somas. Short current pulses in the range of 50μs have been shown to preferentially activate somas, but the low specificity may limit practical applications. In this paper, we explored decreasing pulse durations down to 10μs for achieving focal activation, i.e., a large differentiation between axonal and somatic activation in epiretinal configuration. We determined thresholds for pulses ranging between 10 and 500μs in retinal ganglion cells of both wild-type and photoreceptor-degenerated mouse retina. Ex-vivo stimulation using biphasic rectangular pulses was performed using a custom-built modified Howland-type current-controlled stimulator and a microelectrode. We demonstrate reliable direct activation of retinal ganglion cells using 10μ s pulses for both somatic and axonal electrode positions. Cells from wild-type and photoreceptor-degenerated retinas exhibited similar thresholds. Axonal thresholds were significantly higher for all pulse durations, with the ratio between axonal and somatic thresholds strongly increasing with decreasing pulse duration (1.32 and 4.39 for pulse durations of 500 and 10μs, respectively). Computational modeling points to somatic polarization as the underlying mechanism for lower somatic thresholds. Our results demonstrate focal activation with pulses in the range of 10μs as a potential strategy to avoid the long-standing problem of axonal co-activation in epiretinal implants.
Files
Model_Patch_Koppenwallner_et_al.zip
Additional details
Related works
- Is source of
- Publication: 10.1109/TNSRE.2025.3529940 (DOI)
- Is supplement to
- Dataset: 10.48436/dpn2c-ssd67 (DOI)
Funding
- FWF Austrian Science Fund
- Biophysical diversity in retinal ganglion cells P35488
Dates
- Created
- 2025-10-08