Electrical stimulation of mammalian retinal cells with multielectrode arrays. Sekirnjak, C., Hottowy, P., Sher, A., Dabrowski, W., Litke, A. M., & Chichilnisky, E. J. J. Neurophysiology, 95:3311-27, 2006.
abstract   bibtex   
The Salk Institute for Biological Studies, San Diego, CA, USA. Existing epiretinal implants for the blind are designed to electrically stimulate large groups of surviving retinal neurons using a small number of electrodes with diameters of several hundred microm. To increase the spatial resolution of artificial sight, electrodes much smaller than those currently in use are desirable. In this study we stimulated and recorded ganglion cells in isolated pieces of rat, guinea pig, and monkey retina. We utilized micro-fabricated hexagonal arrays of 61 platinum disk electrodes with diameters between 6 and 25 microm, spaced 60 microm apart. Charge-balanced current pulses evoked one or two spikes at latencies as short as 0.2 ms, and typically only one or a few recorded ganglion cells were stimulated. Application of several synaptic blockers did not abolish the evoked responses, implying direct activation of ganglion cells. Threshold charge densities were typically below 0.1 mC/cm(2) for a pulse duration of 100 micros, corresponding to charge thresholds of less than 100 pC. Stimulation remained effective after several hours and at high frequencies. To demonstrate that closely spaced electrodes can elicit independent ganglion cell responses, we utilized the multi-electrode array to stimulate several nearby ganglion cells simultaneously. From these data we conclude that electrical stimulation of mammalian retina with small-diameter electrode arrays is achievable and can provide high temporal and spatial precision at low charge densities. We review previous epiretinal stimulation studies and discuss our results in the context of 32 other publications, comparing threshold parameters and safety limits.
@article{ Sekirnjak_etal06,
  author = {Sekirnjak, C. and Hottowy, P. and Sher, A. and Dabrowski, W. and
	Litke, A. M. and Chichilnisky, E. J.},
  title = {Electrical stimulation of mammalian retinal cells with multielectrode
	arrays},
  journal = {J. Neurophysiology},
  year = {2006},
  volume = {95},
  pages = {3311-27},
  abstract = {The Salk Institute for Biological Studies, San Diego, CA, USA. Existing
	epiretinal implants for the blind are designed to electrically stimulate
	large groups of surviving retinal neurons using a small number of
	electrodes with diameters of several hundred microm. To increase
	the spatial resolution of artificial sight, electrodes much smaller
	than those currently in use are desirable. In this study we stimulated
	and recorded ganglion cells in isolated pieces of rat, guinea pig,
	and monkey retina. We utilized micro-fabricated hexagonal arrays
	of 61 platinum disk electrodes with diameters between 6 and 25 microm,
	spaced 60 microm apart. Charge-balanced current pulses evoked one
	or two spikes at latencies as short as 0.2 ms, and typically only
	one or a few recorded ganglion cells were stimulated. Application
	of several synaptic blockers did not abolish the evoked responses,
	implying direct activation of ganglion cells. Threshold charge densities
	were typically below 0.1 mC/cm(2) for a pulse duration of 100 micros,
	corresponding to charge thresholds of less than 100 pC. Stimulation
	remained effective after several hours and at high frequencies. To
	demonstrate that closely spaced electrodes can elicit independent
	ganglion cell responses, we utilized the multi-electrode array to
	stimulate several nearby ganglion cells simultaneously. From these
	data we conclude that electrical stimulation of mammalian retina
	with small-diameter electrode arrays is achievable and can provide
	high temporal and spatial precision at low charge densities. We review
	previous epiretinal stimulation studies and discuss our results in
	the context of 32 other publications, comparing threshold parameters
	and safety limits. },
  issue = {6}
}

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