title: Inconsistent channel bandwidth estimates suggest winner-take-all nonlinearity in second-order vision.
abstract: The processing of texture patterns has been characterized by a model that postulates a first-stage linear filter to highlight a component texture, a pointwise rectification stage to convert contrast for the highlighted texture into mean response strength, followed by a second-stage linear filter to detect the texture-defined pattern. We estimated the spatial-frequency bandwidth of the second-stage filter mediating orientation discrimination of orientation-modulated second-order gratings by measuring threshold elevation in the presence of filtered noise added to the modulation signal. This experiment yielded no evidence for frequency tuning. A second experiment, in which subjects had to detect similar second-order gratings while judging their modulation frequency, produced bandwidth estimates of 1-1.5 octaves, similar to estimated bandwidths of first-order channels. We propose that an additional dominant-response-selection nonlinearity can account for these apparently contradictory results.
authors: Department of Psychology, New York University, USA.
authors: Zachary M
authors: ZM
authors: Westrick
authors: Christopher A
authors: CA
authors: Henry
authors: Michael S
authors: MS
authors: Landy
mesh_terms: D015350:Contrast Sensitivity / Q000502:physiology; D006801:Humans; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010470:Perceptual Masking / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D012684:Sensory Thresholds / Q000502:physiology