Red/Green Color Naming Declines in the Periphery. a??Bluea??/a??Yellowa?? Does Not. What Happens in Visual Search?

摘要

The ability to name red and green declines earlier in the periphery than the ability to name blue and yellow (Hansen, Pracejus, & Gegenfurtner, 2009; Newton & Eskew, 2003). This is thought to be due to differences in retinal wiring. In the fovea, midget retinal ganglion cells receive a single L or M cone input to their central receptive fields and multiple, random, cone input to the surround, yielding chromatic opponency. In the periphery, however, midgets receive multiple cone central input, reducing chromatic opponency (Gunther & Dobkins, 2002; Mullen & Kingdom, 1996, 2002), and apparently also reducing subjects' ability to name red and green stimuli. The ability to name blue and yellow (unique blue and yellow or retinal/physiological violet and chartreuse), however, remains farther into the periphery. These colors are processed by the small bistratified cells, which receive S vs. L+M cone input throughout their entire receptive fields, without center/surround organization, across the entire retina. Thus, a??bluea??/a??yellowa?? performance would not be predicted to vary with eccentricity. Here we test the effect of this red/green peripheral drop-off in a visual search task. We first mapped out color naming performance, and found that red/green performance declines sharply beginning around 40?° eccentricity, whereas violet/chartreuse performance declines less sharply around 45a??50?°. In a feature visual search task (e.g., red target dot amongst green distractor dots; twelve, 2.5?° diameter dots; 0, 20, and 45?° eccentricity; 12 subjects), these differences in retinal wiring significantly impaired red/green visual search more than violet/chartreuse visual search at 45?°.