Cite as:
Krebs W K, Essock E A, Buttrey S E, Sinai M J, McCarley J S, 2000, "An oblique effect of chromatic gratings measured by color-mixture thresholds" Perception 29(8) 927 – 935
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An oblique effect of chromatic gratings measured by color-mixture thresholds

William K Krebs, Edward A Essock, Samuel E Buttrey, Michael J Sinai, Jason S McCarley

Received 30 November 1999, in revised form 3 April 2000

Abstract. Contrast sensitivity is lower for obliquely oriented achromatic gratings than for vertical or horizontal gratings at high spatial and low temporal frequencies. Although this response is suggestive of mediation by P-pathway cortical correlates, no clear sensory (ie class 1) oblique effect has been demonstrated with isoluminant chromatic stimuli. In the present experiment, a two-alternative forced-choice detection task was used to measure observers' sensitivity to spatio-temporal sinusoids varying in orientation and color contrast. A maximum-likelihood method fit ellipses to the thresholds, with the length of each ellipse taken as a measure of chromatic contrast sensitivity at isoluminance, and the width as luminance contrast threshold. A chromatic oblique effect was observed at about 3 cycles deg^-1 suggesting an orientation bias within the cortical stream conveying P-cell activity.

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