relatively large value of J1does not restrict the growth of the network response with increasing stimulus strength. Thus, the anisotropic tuning introduced by the external input and the recur-rent interactions act cooperatively to raise the network 's response to the stimulus hue, and competitively to tune its selectivity. In contrast, J 0acts cooperatively with the external stimulus to sharpen the curves. As shown in Figure 11, the tuning curves narrow with decreasing values of J0, that is, with an increase in the relative strength of global inhibition to global excitation, a trend which is conserved for various stimulus strengths. Furthermore, there is no trend reversal at T= 0. Rather, for much of the parameter space, J0acts with the thresholding to sharpen the tuning curves, as is illustrated in Figure 12. This could be expected from the fact that at each point throughout the dynamics, both Tand J0act isotropically on all hue preferences, lowering or raising the input for all con-tributing neurons. However, this commonality also means that for | T|> >| c| (where the effect of TonΔcsaturates, as explained above), the thresholding suppresses the role of J0, analogous to the competition between cand J1. Finally, Figures 11 and12also show that increasing the global inhibition acts to reduce the value of a∞(θ/C22) for all cand T. Figure 11. Effect of J0on the tuning curve properties for varying stimulus strengths. β=1, T=-2,J1= 2, and θ/C22=0. ( A ) c=1. ( B ) c=6. Figure 12. Effect of J0on the tuning curve properties for varying values of T. β=1, c=1, J1= 2, and θ/C22=0. ( A ) T=-5. (B) T= 0. 2. Network Neuroscience 694Pattern forming mechanisms of color vision Downloaded from http://direct. mit. edu/netn/article-pdf/7/2/679/2118501/netn_a_00294. pdf by guest on 09 August 2024 