Dopaminergic amacrine cells in the inner nuclear layer and ganglion cell layer comprise a single functional retinal mosaic

Abstract

Many types of retinal neuron are distributed in an orderly manner across the surface of the retina. Indeed, the existence of such regularity amongst a population of neurons, termed a retinal mosaic, may be a defining feature of functionally independent types of retinal neuron. We have examined the spatial distribution of dopaminergic amacrine cells in the ferret retina both in the inner nuclear layer (INL) and in the ganglion cell layer (GCL) to determine whether the cells in each layer form an independent retinal mosaic as evidence of whether they should be considered as two separate types. Ferret retinas contain approximately 1,900 dopaminergic amacrine cells, of which 27% are located in the GCL, and the rest in the INL. Based on analysis of their Voronoi domains as well as autocorrelation analysis and tests for complete spatial randomness, we found that the distribution of INL cells was statistically regular, while that of the GCL cells was not. However, by using cross-correlation analysis, these two groups of cells were found to be spatially dependent: an exclusion zone was detected in the cross-correlogram of roughly the same size as that found in the autocorrelograms of both INL and GCL cells. Such a pattern would be expected if dopaminergic amacrine cells in the INL and GCL were members of a single regular population differing only in their somatic depth. By using computer simulations, we tested this hypothesis directly, confirming that a random assignment of 27% from the total population produces cross-correlograms that are indistinguishable from those of the biological mosaics. We conclude, therefore, that the cells in the two layers form a single functional population; those in the GCL appear to be misplaced. Somatic positioning with respect to depth within the retina is not, by itself, a reliable guide for functional classification.

Topographic Arrangement of S-cone Photoreceptors in the Retina of the Diurnal Nile Grass Rat (Arvicanthis niloticus)

“…51 Absence of cell body-specific labels for each cone subtype led us to rely on markers expressed in the OS to map cone mosaics in A. niloticus. This approach revealed contrasting spatial arrangements between cone subtypes: the S-cone mosaic is distinctly irregular (with nearest-neighbor RI and Rn indexes just above the theoretical upper limit for randomness 52 ), whereas that of the M/L-cones is more ordered. Among rodents, such dissimilar patterning has been described recently in the diurnal agouti, Dasyprocta aguti.…”

Spatial patterning of cholinergic amacrine cells in the mouse retina

“…The NN analysis considers the relationship between a cell and only one of its neighbors, and consequently does not always discriminate real distributions of nerve cells from random distributions (Eglen et al, 2003). This was clearly the case with cholinergic amacrine cells in the GCL, for when VD analysis was conducted the average VDRI for the INL was again greater than that for the GCL (Fig.…”

Two types of Drosophila R7 photoreceptor cells are arranged randomly: A model for stochastic cell‐fate determination

“…Recent work examining the distribution of dopaminergic amacrine cells in the ferret retina utilized the bivariate L-function in individual patterns (Eglen et al, 2003). The L-function is particularly well suited for the present studies, because it is a sensitive method for distinguishing between CSR, clustering (aggregation) and regularity (repulsion), and is useful for detecting both local and global deviations from CSR and independence.…”