Irregular S-cone mosaics in felid retinas. Spatial interaction with axonless horizontal cells, revealed by cross correlation

In most mammals short-wavelength-sensitive (S) cones are arranged in irregu lar patterns with widely variable intercell distances. Consequently, mosaic s of connected interneurons either may show some type of correlation to pho toreceptor placement or may establish an independent lattice with compensat ory dendritic organization. Since axonless horizontal cells (A-HC's) are su pposed to direct all dendrites: to overlying cones, we studied their spatia l interaction with chromatic cone subclasses. In the cheetah, the bobcat, a nd the leopard, anti-S-opsin antibodies have consistently colabeled the A-H C's in addition to the S cones. We investigated the interaction between the two cell mosaics, using autocorrelation and cross-correlation procedures, including a Voronoi-based density probe. Comparisons with simulations of ra ndom mosaics show significantly lower densities of S cones above the cell b odies and primary dendrites of A-HC's. The pattern results in different lon g-wavelength-sensitive-L- and S-cone ratios in the central versus the perip heral zones of A-HC dendritic fields. The existence of a related pattern at the synaptic level and its potential significance for color processing may be investigated in further studies. (C) 2000 Optical Society of America [S 0740-3232(00)02203-1].