Spatially patterned electrical stimulation of the retina for improved specificity

Current retinal prostheses suffer from a lack of spatial specificity, resulting in indiscriminate stimulation of many distinct retinal ganglion cell (RGC) types over a large region. Re-creation of the complex spatiotemporal activity patterns of retinal ganglion cells requires single-cell spatial resolution, which is difficult to achieve with monopolar stimulation, even using high-density electrode arrays. Here we investigate the potential of spatial patterns of current injection for improving spatial specificity. We found that current injection through neighboring electrodes modulates RGC activation thresholds, and that this modulation can be described by a simple empirical model. Such a model could be used to determine optimal spatial patterns of current injection to activate a target RGC without also activating other nearby RGCs.