The size and shape of rod and cone centres of cat retinal ganglion cells.

Receptive field centres of cat retinal ganglion cells, as mediated by rod and by cone inputs, were mapped as contours of iso-sensitivity at a mid-mesopic adapting luminance using, respectively, 452 nm-blue and 578 nm-yellow narrow-band lights at an intensity 1 log unit above threshold for the most sensitive locus. Based on the sizes and shapes of mapped or rod and cone centres for 74 ganglion cells, four receptive field centre categories were distinguished. Cone and rod centres were usually elliptical, and in almost 60% of cells the major axis through the receptive field centre was oriented within +/- 20 degrees of horizontal. In 69%, rod and cone centres were non-concentric, 66% rod and cone centres were non-concentric, 66% had larger rod than cone centres - area ratios ranging from 0.6 : 1 to 2.9 : 1, and in only two cases was the rod centre actually smaller than the cone centre.