The retina is part of the central nervous system and an ideal region to study information processing in the brain. It is accessible, well documented, and studied by researchers spanning the clinical, experimental, and theoretical sciences. Image processing in the retina begins in the outer plexiform layer, where bipolar, horizontal, and photoreceptor cells interact. The goal of this research is to mathematically model, in detail, the subcircuits of the outer plexiform layer, capturing spatio-temporal dynamics on two spatial scales: the scale of an individual synapse and the scale of the receptive field. The availability of electrophysiological, anatomical, and molecular biological data provides a rare opportunity to develop a complex multiscale model for the system. Mathematical modeling will be used to discover the functional impact of various circuitry elements, much the way an experimentalist does with selective pharmacological agents, except that not all the agents that are needed actually exist. A primary objective is to explore two competing hypotheses for explaining synaptic feedback effects that are observed experimentally in the outer plexiform layer of the retina. Specifically, the project will investigate if feedback effects in the cone photoreceptor's synapse are driven by electrical or chemical mechanisms, or both. New insights into the understanding of retinal circuitry from this project will impact research in health and medicine, including biomedical engineering, image processing, visual psychophysics, and pharmacology. The modeling and computational techniques resulting from this project will provide efficient and innovative approaches for other problem areas in applied mathematics and engineering.
