The Neural Control of Vision
H. The Function of the Midget and Parasol Channels in Vision

Figure 30 shows that inactivation of either the parvo or magnocellular layers of the LGN has little effect on the responses of this complex cell in V1. However, when both regions are inactivated at the same time in the LGN, the cell no longer responds. This inference is that this cell gets a convergent input from the midget and parasol systems. Many cells do this, but also many cells get a unique input from either of these systems. In another series of experiments in John Maunsell's laboratory the inactivation of LGN layers was examined while recording in V4 and MT. These studies showed that there is input to V4 from both systems and that MT receives a more profuse input from the parasol than the midget system.