Functional Connectivity Map of Retinal Ganglion Cells for Retinal Prosthesis
Jang Hee Ye1,3, Sang Baek Ryu2,3, Kyung Hwan Kim2,3, and Yong Sook Goo1,3
1Department of Physiology, Chungbuk National University School of Medicine, Cheongju 361-763, 2Department of Biomedical Engineering, College of Health Science, Yonsei University, Wonju 220-710, 3Nano Artificial Vision Research Center, Seoul National University Hospital, Seoul 110-744, Korea
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. Therefore, we examined how retinal ganglion cells (RGCs) in in-vitro retinal preparation act together to encode a visual scene with multielectrode array (MEA). Simultaneous recording of many RGCs with MEA showed that nearby neurons often fired synchronously, with spike delays mostly within 1 ms range. This synchronized firing - narrow correlation - was blocked by gap junction blocker, heptanol, but not by glutamatergic synapse blocker, kynurenic acid. By tracking down all the RGC pairs which showed narrow correlation, we could harvest 40 functional connectivity maps of RGCs which showed the cell cluster firing together. We suggest that finding functional connectivity map would be useful in stimulation encoding strategy for the retinal prosthesis since stimulating the cluster of RGCs would be more efficient than separately stimulating each individual RGC.