Response of Photoreceptors, Dynamic Modeling of Adaptation and Saturation

Photoreceptors have the ability to generate biological responses as a result of stimulation via light. The purpose of this research project is to mathematically model the photoreceptor responses such that we are able to quantitatively capture its key aspects, like the observed adaptation over time and saturation under extreme stimulus. Past photoreceptor models were examined and modified to yield a new dynamic model that was able to provide excellent fits to response of the retinal cells under a variety of stimulus conditions, such as bright and “dark” flashes of light on top of some given initial “background” lighting. Our analysis strongly suggests that just a direct coupling of membrane potential to light is not sufficient to capture the behavior of photoreceptors. Nonlinear coupling between the membrane potential and some “internal” variable that controls adaptation in the cell is necessary to accurately predict the photoreceptor response. On one hand our research may provide insight into the microphysical processes inside the cell, and on the other, help improve exploring the complexities of neural networks.