Fig. 6.

One-dimensional receptive field profiles of two models ON ganglion cells measured with cone specific straight line stimuli. Red and green curves correspond to L and M cone-isolating stimuli, respectively. The curves with open circles were generated with active model amacrine cells. The curves with closed circles depict the profiles with the amacrine cell signals switched off. The curves with Xs depict signals from the model amacrine cells. (A)The profiles for model ganglion cell #870 with an L ON center. (B)The profiles for model ganglion cell #413 with an M ON center. Note the negative going regions in both responses to stimulation of the central cone type without amacrine cells. (C) Fig. 6C illustrates the role of the model amacrine cells. The curves marked with open circles, red for L stimulus and green for the M stimulus, depict the summed signal of 4 ON and 4 OFF amacrine cells that provide input to model ganglion cell #870. A comparison of the peak values shows the presence of a bias. The negative response of the OFF amacrine cell to the M stimulus is larger in absolute value than the positive response of the ON amacrine cell, and the opposite is true for the L stimulus. Curves with Xs depict the sums of ON and OFF signals for both the stimuli. These curves differ from similar curves in Fig 6A only by scale; this is attributable to slight differences in the amplification factors.