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Joseph Corbo; The cone photoreceptor mosaics of the avian retina. Journal of Vision 2010;10(15):4. doi: 10.1167/10.15.4.
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© ARVO (1962-2015); The Authors (2016-present)
The avian retina possesses one of the most sophisticated cone photoreceptor systems among vertebrates. Birds have five types of cones including four single cones which support tetrachromatic color vision and a double cone which is thought to mediate achromatic motion perception. Despite this richness, very little is known about the spatial organization of avian cones. We recently found that the five cone types of the chicken independently tile the retina as highly ordered mosaics with a characteristic spacing between cones of the same type. Although cones show spacing interactions which are cell type-specific, all cone types use the same density-dependent yardstick to measure intercone distance. Despite the lack of heterotypic repulsion between cones of the same type, the regularity of the individual cone mosaics appears to be interdependent. As a consequence, it is possible to use a single parameter, the global regularity index, to define the regularity of all five cone mosaics. The presence of similar cone distributions in three additional avian species suggests that these patterning principles are universal among birds. Since regular photoreceptor spacing is critical for uniform sampling of visual space, the cone mosaics of the avian retina represent an elegant example of the emergence of adaptive global patterning secondary to simple local interactions between individual photoreceptors.
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