The Midget and Parasol Systems

Abstract The midget and parasol systems originate in the retina. The midget retinal ganglion cells are most numerous among the ganglion cells; they have small receptive fields, especially in the foveal area, and can process fine detail as well as color information. The parasol ganglion cells have larger receptive fields than the midget ganglion cells and receive convergent input from the red and green cones and bipolar cells. The parasol ganglion cells are very sensitive and play a central role in processing motion information. Both of these cell types come in ON and OFF sub-varieties. This chapter has four sections. Section A describes the basic organization of the midget and parasol systems. Section B delineates the central projections of these two systems. Section C describes the behavioral studies that assess the functions of midget and parasol systems. In section D a summary is provided of the topics covered in the chapter.