April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Optimal Electrical Stimuli for Activation of Retinal Ganglion Cell Populations
Author Affiliations & Notes
  • Archana Jalligampala
    Institute of Ophthalmic Research, University of Tuebingen, Tuebingen, Germany
    Graduate Training Centre of Neuroscience, University of Tüebingen, tuebingen, Germany
  • Daniel Llewellyn Rathbun
    Institute of Ophthalmic Research, University of Tuebingen, Tuebingen, Germany
    Center for Integrative Neuroscience, University of Tuebingen, tuebingen, Germany
  • Eberhart Zrenner
    Institute of Ophthalmic Research, University of Tuebingen, Tuebingen, Germany
    Center for Integrative Neuroscience, University of Tuebingen, tuebingen, Germany
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 1819. doi:
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      Archana Jalligampala, Daniel Llewellyn Rathbun, Eberhart Zrenner; Optimal Electrical Stimuli for Activation of Retinal Ganglion Cell Populations. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1819.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: Electrical responsiveness of retinal ganglion cells (RGCs) is a nonlinear function of both voltage and duration. We looked for the voltage/duration pair that activates the largest possible fraction of RGCs in adult wild-type (wt) and rd10 mice.

Methods: RGC spiking responses were recorded in vitro from adult (P28-P33) wt (C57BL/6) and degenerating (rd10) retinas, using a planar multi-electrode array (60 electrodes, 200µm pitch, 30µm Ø, MCS GmbH). Epiretinal electrical stimuli were delivered via one electrode while the other electrodes served for recording. Stimuli consisted of square-wave, monophasic voltage pulses (cathodic & anodic) in incremental blocks (0.1V-2.5V) with randomized pulse durations (.06ms-5ms) for each block. From these responses rastergrams, peri-stimulus time histograms, and firing rate response surfaces over the voltage vs. duration stimulus space were generated. We defined ‘nearby cells’ as cells recorded on the 8 electrodes around the stimulation electrode (stimulation distance ≈100-383µm). Significance was determined by the Kruskal-Wallis multiple comparisons test (p<.05).

Results: Threshold voltages did not differ between wt and rd10 at any duration. By sampling a complete voltage/duration panel for each RGC, we were able to determine the fraction of the recorded population that responded to each unique stimulus with a rate both above threshold and below saturation. Pulses of -2.3V and .84ms activated the majority (>80%) of nearby RGCs in both wt and rd10 retinas.At a fixed voltage of -1.4V (within the water electrolysis window) at least 60% of RGCs could be activated at 2.4ms in wt and rd10.We unexpectedly saw a tendency for voltage thresholds to increase with duration from .06ms up to 1ms for both mouse strains. While this tendency was not always significant for nearby cells (N≈100), it was significant when cells from additional electrodes (stimulation distance >383µm) were included (N>1000) reflecting its subtle nature. The majority of cells strongly preferred cathodic pulses in both wt and rd10 mice.

Conclusions: This study is the most complete examination to date of electrical response thresholds in rd10 retina. Accordingly, we propose tentative stimulation parameters appropriate for activation of the largest possible fraction of rd10 and wt RGCs in our continued studies of electrical stimulation of the retina.

Keywords: 508 electrophysiology: non-clinical • 691 retina: proximal (bipolar, amacrine, and ganglion cells) • 696 retinal degenerations: hereditary  
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