Artikel
What is the optimal electrical stimulus for most RGCs?
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Veröffentlicht: | 13. Februar 2014 |
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Gliederung
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Objective: To determine optimal stimuli for wild type (wt) and rd10 retinas.
Material and Methods: Retinal ganglion cell (RGC) spiking responses were recorded in vitro from patches of wt (C3H & C57BL/6) and degenerated (rd10) retina, using a planar multi-electrode array (MEA, 60 electrodes, 200µm interelectrode distance, 30µm diameter, MCS, GmbH). Epiretinal stimuli were delivered via one of the 60 electrodes while the other electrodes recorded electrically-evoked responses. Stimuli consisted of square-wave, monophasic voltage pulses in incremental blocks (0.1V-2.5V) with randomized pulse durations. Responses were processed & analyzed offline using spike sorting software (Offline Sorter & NeuroExplorer, Plexon Inc, TX) and custom Matlab scripts (The Mathworks, Natick, MA) to generate rastergrams, peri-stimulus time histograms, and response surfaces over the 2D stimulus space.
Results: Electrical responsiveness of RGCs is a nonlinear function of both voltage and duration. By sampling a complete response surface for each RGC, we were able to determine the fraction of the recorded population that would respond to each unique stimulus at a rate both above threshold and below saturation. This allowed us to identify a small number of optimal stimuli that can be used in future studies to activate the majority of RGCs.
Discussion: Our findings present one of the first examinations of electrical stimulation in rd10 retina. Based on these findings, we propose tentative stimulation parameters appropriate for activation of rd10 and wt retina in our continued development of more efficient stimuli for the Tübingen retinal prosthesis.
Acknowledgements: Kerstan Stiftung; Neuro-Ophthalmologische Gesellschaft; Pro-Retina; BMBF, FKZ: 01GQ1002; DFG, EXC307