Purchase this article with an account.
Yung-Chung Lin, Chien-Chung Chen; Spatial summation of chromatic information. Journal of Vision 2005;5(8):1020. doi: 10.1167/5.8.1020.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: We investigated the extent and the shape of the receptive fields of chromatic detectors by observing the detection thresholds for spatial patterns with different size, shape and chromaticity.
Method: The stimuli were either Gabor patches (4c/deg, sine phase, horizontal) or Gaussian spots. The contrast detection thresholds were measured as a function of the length and the width of the Gaussian envelope to determine the size and the aspect ratio of the detector. The scale parameters (“standard deviation”) of the Gaussian envelope varied from 0.01 to 0.45 deg in either vertical or horizontal direction or both. The chromaticity modulated either in L−M, S or L+M cone contrast directions. The threshold was measured with a 2AFC paradigm and QUEST adaptive threshold seeking algorithm.
Result: For Gaussian stimuli in all color directions, the threshold decreased with the length or the width from 0.01 and 0.15 deg. with a slope −0.5 on a log-log plot. The threshold then reduced slowly as the length further increased. The threshold for the L+M Gabor patch revealed an elongated property as the detection threshold function leveled at a greater extent in length than in width. The threshold for the L−M or the S-cone modulated Gaussian showed an isotropic property with the threshold curve leveled at about the same point for both length and width.
Conclusion. While the luminance contrast detectors are elongated, the chromatic detectors are isotropic. In addition, the spatial extents for Gaussian and Gabor summation are about equal. It suggested a second order envelope detector involved in the chromatic contrast detection.
This PDF is available to Subscribers Only