Figure 2. a, b, Phase portraits of Equation 7 for a dichromatic network with red and green photoreceptors, and with the parameters wHR=1.5,wRH=−1.7,wHG=0.9,wGH=−1.1,S(λ)=N(λ=380,1)
, and (a) wGR=wRG=0
corresponding to Type-I and (b) wGR=wRG=1.8
, corresponding to a Type-II network. c, Bifurcation diagram of hR for the intercone coupling parameters wGR=wRG=[1,2.5]
. d, Normalized phase portraits for red and green responses with two stable fixed points at a distance DRG (dashed line). The plot on the left (right) corresponds to the phase portrait of a Type-II network with the excitatory couplings wRG=wGR=2.0
(wRG=wGR=2.2
). e, Distance DRG between stable fixed points in the phase plane as a function of the excitatory coupling; the parameters are the same as in c. The distribution on the right corresponds the SD, ΔDRG
, obtained from zebrafish experimental data; the dashed red line is the mean error. f, Trichromatic sketch of a fully connected network with an external stimulus, S(λ). R: red cones, G: green cones, B: blue cones, H: horizontal cells. Solid black arrows represent inhibitory synaptic connections on cones from horizontal cells. Dashed black arrows represent excitatory synaptic connections between cones. g, Proportion of networks exhibiting multistability. Color intensity represents the normalized sum over the discrete interval wRG = [0.1, …, 2.0], for a fixed combination of the excitatory parameters, wGR and wBR. All points correspond to the same combination of inhibitory parameters used before.