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Eye strips images of all but bare essentials before sending visual information to brain, UC Berkeley research shows
28 March 2001

By Robert Sanders, Media Relations

Neurobiologist Frank Werblin, professor of molecular and cell biology, UC Berkeley. Robert Sanders photo


Berkeley — The eye as a camera has been a powerful metaphor for poets and scientists alike, implying that the eye provides the brain with detailed snapshots that form the basis for our rich experience of the world.

Recent studies at the University of California, Berkeley, however, show that the metaphor is more poetic than real. What the eye sends to the brain are mere outlines of the visual world, sketchy impressions that make our vivid visual experience all the more amazing.

Listen to Frank Werblin
explaining the movie outputs of the eye (audio with photo).

"Even though we think we see the world so fully, what we are receiving is really just hints, edges in space and time," said Frank S. Werblin, professor of molecular and cell biology in the College of Letters & Science at UC Berkeley. Werblin, a member of the Helen Wills Neuroscience Institute, is part of UC Berkeley's Health Sciences Initiative, a collaboration among researchers throughout the campus to tackle some of today's major health problems.

The brain interprets this sparse information, probably merging it with images from memory, to create the world we know, he said.

In a paper in this week's issue of Nature, doctoral student Botond Roska, M.D., and Werblin provide evidence for between 10 and 12 output channels from the eye to the brain, each carrying a different, stripped-down representation of the visual world.

Seven of the dozen separate movies that the eye extracts from a scene and sends to the brain.
Frank Werblin image

See video page showing how the eye processes images and sends them to the brain.

"These 12 pictures of the world constitute all the information we will ever have about what's out there, and from these 12 pictures, which are so sparse, we reconstruct the richness of the visual world," Werblin said. "I'm curious how nature selected these 12 simple movies and how it can be that they are sufficient to provide us with all the information we seem to need."

While scientists have known that the eye forwards 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 chip, called a Cellular Neural Network (CNN) Universal Machine, was invented in 1992 by Roska's father, Tamás Roska, and Leon O. Chua, a professor of electrical engineering and computer sciences at UC Berkeley.

"The biology we are learning is going into improving the chip, which is getting more and more similar to the mammalian retina," Roska said. "Nevertheless, a bionic eye is a far-fetched notion until someone figures out how to connect it to the neural circuitry of the brain."