Cone Excitations and Color Vision
- *Departments of Ophthalmology and Physiology, University of California, San Francisco, California 94143; †Department of Neurobiology, Stanford Medical School, Stanford, California 94305; ‡Department of Chemistry, University of California, Berkeley, California 94702; §Department of Chemistry, State University of Leiden, Leiden, The Netherlands
This extract was created in the absence of an abstract.
Excerpt
The brain computes the colors in visual images by comparing the excitations of three types of retinal cones, each sensitive in a different region of the spectrum. Nearly two centuries after trichromacy was enunciated by Thomas Young (1802), Nathans et al. (1986) established its molecular basis by cloning the genes for the three cone pigments. Despite this achievement, it has been difficult to define the wavelength dependence of the cone excitations and to delineate the molecular mechanism of wavelength selectivity. Microspectro-photometry (for review, see Bowmaker 1984, 1990) has been used to measure the spectral absorption of single cones, but the small quantity of pigment in one cell restricts the measurements to wavelengths where the absorption is strong. Suitable expression systems for the cone pigments are not yet available.
We have used physiological methods to study the light-evoked cone excitations of the primate retina. In particular, we have asked:
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How sensitive
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