Retinal origin of orientation maps in visual cortex

The orientation map is a hallmark of primary visual cortex in higher mammals. It is not yet known how orientation maps develop, what function they play in visual processing and why some species lack them. Here we advance the notion that quasi-periodic orientation maps are established by moiré interference of regularly spaced ON and OFF-center retinal ganglion cell mosaics. A key prediction of the theory is that the centers of iso-orientation domains must be arranged in a hexagonal lattice on the cortical surface. Here we show that such pattern is observed in individuals of four different species: monkey, cat, tree shrew and ferret. The proposed mechanism explains how orientation maps can develop without requiring precise patterns of spontaneous activity or molecular guidance. Further, it offers a possible account for the emergence of orientation tuning in single neurons despite the absence of orderly orientation maps in rodents species. It has long been known that the primary visual cortex of higher mammals is organized into functional maps1. One of the most studied is the orientation map, which captures the preferred orientation of neurons across the cortical surface. Optical imaging methods2–3 have revealed that preferred orientation on the cortex changes continuously in a quasi