Article
Electrical receptive field mapping in blind retina using localized electrical stimulation with a subretinal implant
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Published: | March 7, 2016 |
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Objective: To map the electrical receptive fields (eRF) in healthy and blind, photoreceptor-degenerated mouse retina stimulated with a subretinal implant.
Materials and Methods: Ex vivo retina from healthy (wt) and blind (rd1 and rd10) mice were electrically stimulated using a subretinal implant (AMS, Retina Implant AG) driven by light stimulation. Simultaneously retinal ganglion cell (RGC) activity was recorded using a flexible microelectrode array in epiretinal configuration. The eRFs were mapped using narrow stripes of light (70µm) presented at equidistant positions across the implant’s surface, leading to column-wise activation of the implant’s photodiodes and subsequently to electrical stimulation of the retina. RGC activity to repetitive stimulation was analyzed and eRF sizes of individual RGCs were calculated.
Results: The average eRF size of RGCs in wt and rd10 retinas did not differ and the spatiotemporal response patterns of both were comparable. Noteworthy, apart from the most frequently observed ON-type responses, some RGCs showed OFF-type responses and were inhibited by electrical stimulation. Apart from these spatially-confined responses, a small portion of RGCs in rd10 retinas showed spatially-unconfined rhythmic activity as it is observed in rd1 retinas.
Discussion: Evaluation of the eRF sizes and the spatiotemporal response patterns suggests that the inner retinal circuitry in rd10 retinas remains intact to a large degree upon photoreceptor loss. However, the rhythmic spiking in some of the RGCs indicates a partial remodeling of the network. The future challenge is to find out if certain circuits or cell types are preferentially affected and how one could address these by electrical stimulation so that they could still carry meaningful visual information.
Acknowledgment: This work was supported by BMBF Grant No. 1312038. The subretinal microchips were provided by Retina Implant AG. Travel expenses were covered by the Graduate Training Centre of Neuroscience.