Figure 3. Receptive field centre size and sensitivity.

A, centre radius, estimated from difference-of-Gaussian fits, as a function of eccentricity for PC (points), MC (+), blue-on (triangles) and blue-off (filled circles) cells. Centre radius is estimated from achromatic gratings for PC and MC cells, and from S-cone selective gratings for blue-on and blue-off cells. B, comparison of the centre radii estimated from achromatic gratings (x-axis) and S-cone selective gratings (y-axis) in blue-on (triangles) and blue-off (filled circles) cells. C, comparison of the mean centre radius of on- and off-centre PC and MC cells, blue-on cells, and blue-off cells. Means are calculated only from cells with receptive fields located within 10 deg of the fovea. Mean radii (and standard errors of the mean) for the different cell types are: PC-on, 0.0586 (0.0033, n = 80); PC-off, 0.0639 (0.0032, n = 89); MC-on, 0.1291 (0.0138, n = 17); MC-off, 0.1328 (0.0149, n = 15); blue-on, 0.194 (0.0224, n = 44); blue-off, 0.5566 (0. 1821, n = 11). D, centre sensitivity (k_c) plotted as a function of centre radius (r_c). Conventions as in A. E, centre radius of blue-on and blue-off cells in the central 10 deg. Blue-off cells have larger centre radius than most blue-on cells at the same eccentricity. F, distribution of centre radius within the central 10 deg. Note the unimodal distribution. The vertical bar indicates the anatomical range of dendritic field radius divided by 2 (DFR/2) of small bistratified cells over this eccentricity range (Szmajda et al. 2008). This shows that dendritic field radius of small bistratified cells corresponds to approximately ±2 Gaussian standard deviations of the blue-on S-cone mechanism.