title: Luminance spatial frequency differences facilitate the segmentation of superimposed textures.
abstract: Do superimposed textures segregate on the basis of a difference in their luminance spatial frequency? We addressed this question using orientation-gratings, which consist of dense arrays of Gabor micropatterns whose orientations vary sinusoidally across space. Two orientation gratings of the same texture spatial frequency were combined in anti-phase, to produce a 'dual-modulation' orientation grating. Thresholds for detecting the dual-modulation gratings were measured as a function of the difference in Gabor spatial frequency between the two grating components. When the two components were made from the same Gabors, thresholds were relatively high. However a one octave difference in Gabor spatial frequency between the components caused thresholds to fall close to those of single-modulation orientation gratings. The fall in threshold was accompanied by a change in appearance of the stimulus; to that of two transparent, interwoven, flow patterns. We show that these results are incompatible with current Filter-Rectify-Filter models of 'second-order' pattern detection. Rather, they favour the idea that feature analysis precedes texture analysis, with the visual system encoding local orientation content prior to the texture stage.
authors.affiliation: Department of Ophthalmology, McGill Vision Research Unit, 687 Pine Avenue West, Rm. H4-14, Montréal, Canada. fred@jiffy.vision.mcgill.ca
authors.forename: F A
authors.initials: FA
authors.lastname: Kingdom
authors.forename: D R
authors.initials: DR
authors.lastname: Keeble
mesh_terms: D006801:Humans; D008029:Lighting; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D012684:Sensory Thresholds / Q000502:physiology