Fig. 12.

Models describing the hypothesized inputs into a Double-Opponent cell. A, One red-on/green-off Type II cell feeds the center of the Double-Opponent cell. The surround is fed by Type II cells of opposite configuration, green-on/red-off (shown ingray) (adapted from Michael, 1978). Although early studies suggest the existence of red–green Type II cells in the LGN, subsequent investigators have not found them. Thus, although LGN Type II cells may be involved in forming blue–yellow cortical Double-Opponent cells, an alternative model is required for the formation of cortical red–green Double-Opponent cells. For example,B, a group of parvocellular LGN Type I cells whose receptive field centers are dominated by the same cone class (in this case L), could feed the center, whereas the surround could be fed by Type I cells of the opposite configuration (2 cells are shown ingray). A cortical red–green Type II cell would result if the surround were insignificant.