Trichromatic colour opponency in ganglion cells of the rhesus monkey retina.

Two hundred and eleven colour-opponent ganglion cells were studied in the central 10 degrees of the retina of the rhesus monkey, to determine the inputs which they were receiving from different cone mechanisms. Spectral-sensitivity measurements in the presence of neutral and coloured back-grounds showed that 24% of these cells appeared to receive input from all three cone mechanisms. 2. In 3% of the cells, the red-sensitive cone mechanism opposed the blue- and green-sensitive ones. In 18% of the cells, the blue-sensitive cone mechanism opposed the green- and red-sensitive ones. In 3% of the cells, the green-sensitive cone mechanism opposed the blue- and red-sensitive ones. 3. In 12% of the cells receiving opponent green- and red-sensitive cone inputs, responses from the beta-band of the red-sensitive cone mechanism could be detected and distinguished from blue-sensitive cone input. 4. All cells receiving blue-sensitive cone input appeared to be trichromatic. The retinal distribution of cells with trichromatic input and that of cells with beta-band responses seemed to parallel the availability of blue-sensitive cones in the retinal area being considered. 5. The results indicate that trichromatic interactions in the macaque visual system begin in the retina.