Double color-opponent receptive fields of carp bipolar cells

Bipolar cells with double color-opponent receptive fields were found in the carp retina. They were classified into two types depending on their response polarity. In the receptive field center, type I cells showed hyperpolarization to a long wavelength spot (R-) and depolarization to a short wavelength spot (G+), while in the surround they showed R+, G- responses. Type II cells showed responses of opposite polarities to those of type I cells, namely R+ G- in the center, and R- G+ in the surround. From their spectral sensitivity, R components were identified as coming from red-sensitive cones, and G components from green-sensitive cones. These bipolar cells are thought to be the origin of double color-opponent receptive fields of retinal ganglion cells.