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

These finding led the to formulation shown in Figure 39. The proposal is that the midget and parasol systems have evolved to extend our range of vision in different domains, with the midget system extending it in the spatial domain and the parasol system in the temporal domain. The reason two different systems have emerged to accomplish this is due to the fact that the neural requirements to optimize fine spatial vision and fine temporal analysis are in conflict. Properly configured, two systems are much more economical and can do a much better job than a single system could.