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It has been argued that the emergence of roughly periodic orientationpreference maps (OPMs) in the primary visual cortex (V1) of carnivores andprimates can be explained by a so-called statistical connectivity model. Thismodel assumes that input to V1 neurons is dominated by feed-forward projectionsoriginating from a small set of retinal ganglion cells (RGCs). The typicalspacing between adjacent cortical orientation columns preferring the sameorientation then arises via Moir\'{e}-Interference between hexagonal ON/OFF RGCmosaics. While this Moir\'{e}-Interference critically depends on long-rangehexagonal order within the RGC mosaics, a recent statistical analysis of RGCreceptive field positions found no evidence for such long-range positionalorder. Hexagonal order may be only one of several ways to obtain spatiallyrepetitive OPMs in the statistical connectivity model. Here, we investigate amore general requirement on the spatial structure of RGC mosaics that can seedthe emergence of spatially repetitive cortical OPMs, namely that angularcorrelations between so-called RGC dipoles exhibit a spatial structure similarto that of OPM autocorrelation functions. Both in cat beta cell mosaics as wellas primate parasol receptive field mosaics we find that RGC dipole angles arespatially uncorrelated. To help assess the level of these correlations, weintroduce a novel point process that generates mosaics with realistic nearestneighbor statistics and a tunable degree of spatial correlations of dipoleangles. Using this process, we show that given the size of available data sets,the presence of even weak angular correlations in the data is very unlikely. Weconclude that the layout of ON/OFF ganglion cell mosaics lacks the spatialstructure necessary to seed iso-orientation domains in the primary visualcortex.

Can retinal ganglion cell dipoles seed iso-orientation domains in the visual cortex?