Color vision has been studied for centuries, but the molecular and cellular intricacies of its neural circuitry have remained an enigma, until now. As reported in a May issue of the Journal of Neuroscience, Penn researchers, led by Peter Sterling, PhD, have -- for the first time -- determined the wiring, neurochemical pathways, and three-dimensional layout of cells in the retina that are involved in blue-yellow color vision that is evident in all mammals.
Knowledge of this retinal structure and biochemistry will lay the foundation for designing artificial retinas and better understanding rare eye diseases. Using the intact retina of a macaque, the scientists created a three-dimensional map of the location of the blue-yellow cells by taking electron micrographs of 320 cross-sections of the retina.
"We photographed the mosaic of retinal cells piece by piece, analyzed over 2,000 images, and then used a computer program to build up a library of the complete structure," explains Sterling, a professor of neuroscience. "By composing this exacting model, we can now isolate and identify the interacting circuitry between layers of the retina."
The findings of Sterling's group also provide clues to the neural processes at work in red-green vision -- the additional, complementary color-vision system that is found in all Old World primates, including humans. Indeed, anthropologists surmise that the red-green system evolved in these primates to allow them to distinguish red, ripe fruits from green tree foliage and to discriminate gender-specific markings during mating season.
The University of Pennsylvania Medical Center's sponsored research and training ranks third in the United States based on grant support from the National Institutes of Health, the primary funder of biomedical research and training in the nation -- $175 million in federal fiscal year 1997. In addition, for the third consecutive year, the institution posted the highest annual growth in these areas -- 17.6 percent -- of the top ten U.S. academic medical centers.
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