Simulations of X and Y retinal ganglion cell behavior with a nonlinear push-pull model of spatiotemporal retinal processing.
This article describes a nonlinear model of neural processing in the vertebrate retina, comprising model photoreceptors, model push-pull bipolar cells, and model ganglion cells. Previous analyses and simulations have shown that with a choice of parameters that mimics beta cells, the model exhibits X-like linear spatial summation (null response to contrast-reversed gratings) in spite of photoreceptor nonlinearities; on the other hand, a choice of parameters that mimics alpha cells leads to Y-like frequency doubling. This article extends the previous work by showing that the model can replicate qualitatively many of the original findings on X and Y cells with a fixed choice of parameters. The results generally support the hypothesis that X and Y cells can be seen as functional variants of a single neural circuit. The model also suggests that both depolarizing and hyperpolarizing bipolar cells converge onto both ON and OFF ganglion cell types. The push-pull connectivity enables ganglion cells to remain sensitive to deviations about the mean output level of nonlinear photoreceptors. These and other properties of the push-pull model are discussed in the general context of retinal processing of spatiotemporal luminance patterns.
Gaudiano
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Department of Cognitive and Neural Systems, Boston University, MA 02215.
D000222:Adaptation, Physiological; D015350:Contrast Sensitivity / Q000502:physiology; D006801:Humans; D008433:Mathematics; D008959:Models, Neurological; D009415:Nerve Net / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010786:Photoreceptor Cells / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000502:physiology*