Decoding of temporal visual information from electrically evoked retinal ganglion cell activities in photoreceptor-degenerated retinas.

Purpose: To restore visual function via the prosthetic stimulation of retina, visual information must be properly represented in the electrically evoked neural activity of retinal ganglion cells (RGCs). In this study, the RGC responses in photoreceptor-degenerated retinas were shown to actually encode temporal information on visual input when they were stimulated by biphasic pulse trains with amplitude modulation.

Methods: Multiple RGC spike trains were recorded from rd1 mouse retinal patches mounted on planar microelectrode arrays while being stimulated by pulse trains with amplitudes modulated by the intensity variation of a natural scene.

Retinal ganglion cell responses to voltage and current stimulation in wild-type and rd1 mouse retinas.

Retinal prostheses are being developed to restore vision for those with retinal diseases such as retinitis pigmentosa or age-related macular degeneration. Since neural prostheses depend upon electrical stimulation to control neural activity, optimal stimulation parameters for successful encoding of visual information are one of the most important requirements to enable visual perception. In this paper, we focused on retinal ganglion cell (RGC) responses to different stimulation parameters and compared threshold charge densities in wild-type and rd1 mice.

Retinal ganglion cell (RGC) responses to different voltage stimulation parameters in rd1 mouse retina.

Retinal prostheses are being developed to restore vision for the blind with retinal diseases such as retinitis pigmentosa (RP) or age-related macular degeneration (AMD). Since neural prostheses depend upon electrical stimulation to control neural activity, optimal stimulation parameters for successful encoding of visual information are one of the most important requirements to enable visual perception. Therefore, in this paper, we focused on RGC responses to different stimulation parameters in degenerated retina.

Temporal response properties of retinal ganglion cells in rd1 mice evoked by amplitude-modulated electrical pulse trains.

Purpose: The electrophysiological properties of degenerated retinas responding to amplitude-modulated electrical pulse trains were investigated to provide a guideline for the development of a stimulation strategy for retinal prostheses.

Methods: The activities of retinal ganglion cells (RGCs) in response to amplitude-modulated pulse trains were recorded from an in vitro model of retinal prosthesis, which consisted of an rd1 mouse retinal patch attached to a planar multielectrode array. The ability of the population activities of RGCs to effectively represent, or encode, the information on the visual intensity time series, when the intensity of visual input is transformed to pulse amplitudes, was investigated.

Decoding of retinal ganglion cell spike trains evoked by temporally patterned electrical stimulation.

For successful restoration of vision by retinal prostheses, the neural activity of retinal ganglion cells (RGCs) evoked by electrical stimulation should represent the information of spatiotemporal patterns of visual input. We propose a method to evaluate the effectiveness of stimulation pulse trains so that the crucial temporal information of a visual input is accurately represented in the RGC responses as the amplitudes of pulse trains are modulated according to the light intensity. This was enabled by spike train decoding.

Electrically-evoked Neural Activities of rd1 Mice Retinal Ganglion Cells by Repetitive Pulse Stimulation.

For successful visual perception by visual prosthesis using electrical stimulation, it is essential to develop an effective stimulation strategy based on understanding of retinal ganglion cell (RGC) responses to electrical stimulation. We studied RGC responses to repetitive electrical stimulation pulses to develop a stimulation strategy using stimulation pulse frequency modulation. Retinal patches of photoreceptor-degenerated retinas from rd1 mice were attached to a planar multi-electrode array (MEA) and RGC spike trains responding to electrical stimulation pulse trains with various pulse frequencies were observed.

Functional connectivity map of retinal ganglion cells for retinal prosthesis.

Retinal prostheses are being developed to restore vision for the blind with retinal diseases such as retinitis pigmentosa (RP) or age-related macular degeneration (AMD). Among the many issues for prosthesis development, stimulation encoding strategy is one of the most essential electrophysiological issues. The more we understand the retinal circuitry how it encodes and processes visual information, the greater it could help decide stimulation encoding strategy for retinal prosthesis.

Accurate Representation of Light-intensity Information by the Neural Activities of Independently Firing Retinal Ganglion Cells.

For successful restoration of visual function by a visual neural prosthesis such as retinal implant, electrical stimulation should evoke neural responses so that the information on visual input is properly represented. A stimulation strategy, which means a method for generating stimulation waveforms based on visual input, should be developed for this purpose. We proposed to use the decoding of visual input from retinal ganglion cell (RGC) responses for the evaluation of stimulus encoding strategy.

Characterization of retinal ganglion cell activities evoked by temporally patterned electrical stimulation for the development of stimulus encoding strategies for retinal implants.

For successful restoration of visual function by retinal implant, a method for electrical stimulation should be devised so that the evoked activities of retinal ganglion cells (RGCs) should convey sufficient information on visual input. By observing RGC activities under different stimulation constraints, it may be possible to determine optimal pulse parameters, such as pulse rate, intensity, and duration, for faithful transmission of visual information. To test the feasibility of this approach, we analyzed RGC spike trains evoked by temporally patterned stimulation from retinal patches mounted on a planar multielectrode array.

Comparison of electrically-evoked ganglion cell responses in normal and degenerate retina.

Retinal prosthesis is regarded as a promising method for restoring vision for the blind with retinal diseases such as retinitis pigmentosa (RP) and age related macular degeneration (ARMD). Among the several prerequisites for retinal prosthesis to succeed, one of the most important factors is the optimization of electrical stimulation applied through the prosthesis. From the previous study, we showed that the electrical characteristics of diseased retina are different from those of normal retina.

Comparison of voltage parameters for the stimulation of normal and degenerate retina.

Retinal prosthesis is regarded as a promising method for restoring vision for the blind with retinal diseases such as retinitis pigmentosa (RP) and age related macular degeneration (ARMD). Among the several prerequisites for retinal prosthesis to succeed, one of the most important is the optimization of electrical stimuli applied through the prosthesis. Since the electrical characteristics of diseased retina are expected to be different with those of normal retina, we investigated different voltage parameters to stimulate normal and degenerate retina.

Electrical stimulation of isolated rabbit retina.

Several research groups in the world are trying to restore useful vision for the patients of degenerate retina, such as retinitis pigmentosa (RP) and age related macular degeneration (ARMD) with retinal prosthesis. Recently Korean consortium launched for developing retinal prosthesis and as part of Korean retinal prosthesis project we provide preliminary experimental results regarding voltage parameters for the stimulation of isolated retina. Voltage stimulus was delivered via one of the channel of microelectrode array (MEA) and ganglion cell activities were recorded with remained 59 channels.