(A) Conceptual structure of the circuit. Units representing V1 ELCs receive a combination fo excitatory LGN input and two types of orientation-tuned intra-cortical inhibition. The single-opponent (SO) LGN input, which arises from the RGC population in the model (LGN units are not explicitly represented), generates the basic double-opponent (DO) tuning for a red-green edge. The DO inhibition to the ELC reinforces the simple RF structure, and the luminance sensitive (IN) inhibition suppresses responses to luminance edges. (The LGN input has surrounds that arise at random, and are not selective for the opposite color as implied by the icons.)

(B) The set of RGC units from the retinal mesh model (see Ret_Mesh.0) that are presynaptic to the DO unit "in_rg_5_5_1". Open/closed circles indicate OFF/ON center units. Red/Green shows L/M center units. The dim red and green spots in the background show positions of cones not connected to the postsynaptic unit. Note that the left vertical subunit of this vertical orientation preferring unit is composed of Red-OFF and Green-ON units, while the right subunit contains Red-ON and Gree-OFF units.

(C) The set of RGC units from the retinal mesh model that are presynaptic to the IN unit "in_5_5_1". The left vertical subunit of this vertical orientation preferring unit is composed of ony ON inputs, whereas the right subunit is composed of OFF inputs.