Color properties of the motion detectors projecting to the goldfish tectum

Interactions between color channels (long-wave (L), middle-wave (M) and short-wave (S)) in the receptive field of direction-selective (DS) and orientation-selective (OS) ganglion cells (GCs) were investigated with combined selective stimulation of pairs of cone types (L and M, L and S, M and S). In the experiments with DS GCs of both ON and OFF types, it was shown that: (1) M and S channels were synergistic relative to each other and opponent to L channel. (2) Three-parameter signal (from L, M and S cones) is transformed to one-parameter signal at the output of DS GC, thus illustrating the principle of univariance. (3) In the experiments with OS GCs, it was shown that L and M channels were synergistic in the OFF-pathway, while the S channel was opponent to them. Our results suggested that photoreceptor synaptic connectivity of the bipolar cells hypothetically involved in the goldfish OS circuitry substantially differs from connectivity of bipolar cells presumably targeting DS GC. (4) To sum up, the results obtained on DS GCs confirmed the plausibility of proposed DS GC wiring diagrams; as to the OS circuitry of fish retina it still remains unclear and needs further investigation.