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Activity‐regulated cell death contributes to the formation of ON and OFF α ganglion cell mosaics

At maturity, ON and OFF α ganglion cells in the cat retina are arrayed in regular mosaics, with adjacent cells commonly forming ON‐OFF pairs. In the present study, we investigated the role of activity‐mediated ganglion cell death in the formation of such cellular patterns. Because direct measures of ganglion cell mosaics are problematic in the developing retina, we examined the distributions of ON and OFF α cells in the postnatal cat retina by assessing the degree to which cells in closest proximity were of opposite sign (i.e., ON‐OFF pairs). Computer simulations demonstrated that superimposition of two regular distributions results in a high incidence (∼90%) of opposite sign pairs. This is also the case for ON and OFF α cells in the mature retina, reflecting the high degree of regularity exhibited by this cell class. In contrast, during the first postnatal month, α cells displayed a much lower incidence of opposite sign pairs (∼60%), comparable to the superimposition of two simulated random distributions.