We investigated the receptive fields of neurons in the visual cortex from a theoretical viewpoint. It was assumed that if two regions in the visual field are located far apart, local images that fall on these regions are mutually independent. An information-maximization solution was used to determine the optimal receptive field by first assuming a low signal-to-noise ratio limit. We found that the optimal receptive field is a spatially localized, Gabor-function-like receptive field, similar to that of a simple cell.