ELECTRORETINOGRAM OF FRESH-WATER TURTLE: SELECTIVE ADAPTATION TO COLORED LIGHT

Abstract

Previous studies indicating 3 types of cones in the turtle retina, sensitive to red, orange and yellow-green light, are reinforced by measurement of the reduction in responses to test flashes of various colors following light adaptation by the same and different colors. Testing with flashes of fixed color and intensity the effects of exposure to colors ranging from red to blue-green gives curves relating reduction to wave length of adapting light. These curves show steep gradients and shoulders, supporting the evidence from quantitative study of color-shift response. In general, exposure to light of any color depresses subsequent response to the same color more than response to a different color, but strong adapting stimuli with orange light causes more reduction of a red test response than does equally intense adapting stimulus with red light.