title: An oblique effect of chromatic gratings measured by color-mixture thresholds.
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 (i.e. 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 spatiotemporal 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.
authors.affiliation: Naval Postgraduate School, Department of Operations Research, Monterey, CA 93943, USA. william.krebs@faa.gov
authors.forename: W K
authors.initials: WK
authors.lastname: Krebs
authors.forename: E A
authors.initials: EA
authors.lastname: Essock
authors.forename: S E
authors.initials: SE
authors.lastname: Buttrey
authors.forename: M J
authors.initials: MJ
authors.lastname: Sinai
authors.forename: J S
authors.initials: JS
authors.lastname: McCarley
mesh_terms: D000328:Adult; D003118:Color Perception; D015350:Contrast Sensitivity; D006801:Humans; D008297:Male; D010775:Photic Stimulation / Q000379:methods; D011594:Psychometrics / Q000379:methods; D012684:Sensory Thresholds