Abstract
Abstract: :
Purpose:To investigate whether the differential distribution of cone opponency across the visual field influences the latency of color filling–in. We asked whether the steep decline of red–green opponency from center to periphery, and the more gradual loss observed for blue–yellow opponency (Mullen & Kingdom, 2002) influence filling–in process. Methods:Stimuli presented on a computer color monitor. Red–green opponent system tested with red (CIE x=0.60, y=0.32) target and green (CIE x=0.26, y=0.45) surround. Blue–yellow system tested with yellow (CIE x=0.38, y=0.53) target and blue (CIE x=0.15, y=0.06) surround. Target was a circular patch, 0.4° diameter, presented at 6° and 15° eccentricities from central fixation point, alternating between 90º and 270° field positions. Each position was tested 36 times. Subjects were instructed to press "enter" as soon as they considered that the target had disappeared. All subjects gave their informed consent and the Brasília University’s Human Research Ethics Committee has approved this protocol. Results:Red–green stimuli filling–in latencies presented no significant difference (p = 0,561657) between 6° (mean = 8,04s) and 15° (mean = 8,28s) eccentricities. Blue–yellow stimuli filling–in presented a significant difference (p = 7,64E–16) between 6° (mean = 11,97s) and 15° (mean = 7,44s) eccentricities. Conclusions:The same red–green filling–in mean latency found in 6° and 15° eccentricities, for the conditions tested here, suggests that it was not directly influenced by the decline of red–green opponency from center to periphery. This red–green result contradicts the general impression that higher artificial scotoma eccentricities produce faster filling–in latencies (De Weerd et al. 1998). On the other hand, the different latencies obtained for the blue–yellow stimuli from center to periphery corroborate recent evidences of functionally distinct blue–yellow and red–green color systems in human vision.
Keywords: color vision • perception • visual fields