While scientists have known that the eye transmits several parallel representations of the world to the brain, what these are and how they are produced has been a mystery. What we have done, Roska said, is show that the retina creates a stack of image representations, how these image representations are formed and that they are the result of cross-talk between layers of cells in the retina. The results are a big step toward producing a bionic eye employing a unique computer chip that can be programmed to do visual processing just like the retina. The bionic eye s computer chip was invented in 1992 by Roska s father, Tam s Roska, and Leon Chua, professor of electrical engineering and computer sciences. The biology we are learning is going into improving the chip, which is getting more and more similar to the mammalian retina, Roska said.
Ganglion cells are the eye s output cells, forming the optic nerve connecting it to the brain.
By painstakingly measuring signals from more than 200 ganglion cells in the rabbit retina, Roska and Werblin determined that there are about a dozen different populations of ganglion cells, each spanning the full visual space and producing a different movie output. One group of ganglion cells, for example, only sends signals when it detects a moving edge. Another group fires only after a stimulus stops. Another sees large uniform areas, yet another only the area surrounding a figure. Each representation emphasizes a different feature of the visual world an edge, a blob, movement and sends the information along different paths to the brain, Werblin said.