title: Exogenous attention enhances 2nd-order contrast sensitivity.
abstract: Natural scenes contain a rich variety of contours that the visual system extracts to segregate the retinal image into perceptually coherent regions. Covert spatial attention helps extract contours by enhancing contrast sensitivity for 1st-order, luminance-defined patterns at attended locations, while reducing sensitivity at unattended locations, relative to neutral attention allocation. However, humans are also sensitive to 2nd-order patterns such as spatial variations of texture, which are predominant in natural scenes and cannot be detected by linear mechanisms. We assess whether and how exogenous attention--the involuntary and transient capture of spatial attention--affects the contrast sensitivity of channels sensitive to 2nd-order, texture-defined patterns. Using 2nd-order, texture-defined stimuli, we demonstrate that exogenous attention increases 2nd-order contrast sensitivity at the attended location, while decreasing it at unattended locations, relative to a neutral condition. By manipulating both 1st- and 2nd-order spatial frequency, we find that the effects of attention depend both on 2nd-order spatial frequency of the stimulus and the observer's 2nd-order spatial resolution at the target location. At parafoveal locations, attention enhances 2nd-order contrast sensitivity to high, but not to low 2nd-order spatial frequencies; at peripheral locations attention also enhances sensitivity to low 2nd-order spatial frequencies. Control experiments rule out the possibility that these effects might be due to an increase in contrast sensitivity at the 1st-order stage of visual processing. Thus, exogenous attention affects 2nd-order contrast sensitivity at both attended and unattended locations.
authors.affiliation: Department of Psychology, New York University, New York, NY 10003, United States. antoine.barbot@nyu.edu
authors.forename: Antoine
authors.initials: A
authors.lastname: Barbot
authors.forename: Michael S
authors.initials: MS
authors.lastname: Landy
authors.forename: Marisa
authors.initials: M
authors.lastname: Carrasco
mesh_terms: D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology*; D003463:Cues; D004192:Discrimination, Psychological / Q000502:physiology; D006801:Humans; D010364:Pattern Recognition, Visual / Q000502:physiology*; D012399:Rotation; D014794:Visual Fields / Q000502:physiology