The fundamental plan of the retina

The retina, like many other central nervous system structures, contains a h uge diversity of neuronal types. Mammalian retinas contain approximately 55 distinct cell types, each with a different function. The census of cell ty pes is nearing completion, as the development of quantitative methods makes it possible to be reasonably confident that few additional types exist. Al though much remains to be learned, the fundamental structural principles ar e now becoming clear. They give a bottom-up view of the strategies used in the retina's processing of visual information and suggest new questions for physiological experiments and modeling.