Exogenous attention enhances 2nd-order contrast sensitivity

Abstract

Natural scenes contain a rich variety of contours that the visual system extracts to segregrate 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.

Differential effects of exogenous and endogenous attention on second-order texture contrast sensitivity

“…At more peripheral locations, exogenous attention enhanced second-order contrast sensitivity for low second-order spatial frequencies. Barbot et al (2011a) showed that these effects were consistent with the resolution hypothesis (Carrasco et al, 2006; Carrasco & Yeshurun, 2009; Yeshurun & Carrasco, 2000), whereby exogenous spatial attention increases resolution by increasing the sensitivity of the smallest second-order filters at the attended location.…”

“…Note that second-order spatial frequencies separated by an octave or more should activate separate channels (Landy & Oruç, 2002). Similar patterns have been used in psychophysical and neuroimaging studies of texture segmentation (Barbot et al, 2011a; El-Shamayleh & Movshon, 2011; Landy & Oruç, 2002; Larsson et al, 2006). …”

“…Recently, we have documented that exogenous attention helps extract texture-defined boundaries by enhancing contrast sensitivity for second-order information at the attended location, while reducing sensitivity at unattended locations, relative to a neutral condition (Barbot, Landy, & Carrasco, 2011a). However, these effects of attention were a function of the second-order spatial frequency of the stimulus and its eccentricity.…”

Perceptual Learning: Toward a Comprehensive Theory

“…We call this new type of VPL task-irrelevant VPL. A number of subsequent studies have reported task-irrelevant VPL (Barbot et al 2011, Baumann et al 2008, Beste & Dinse 2013, Beste et al 2011, Carrasco et al 2008, Gutnisky et al 2009, Leclercq et al 2013, Leclercq & Seitz 2012, Rosenthal & Humphreys 2010, Seitz & Watanabe 2005, Seitz & Watanabe 2003, Seitz et al 2005b, Tsushima et al 2008, Watanabe et al 2002, Xu et al 2012b, Zhang & Kourtzi 2010, Zhang et al 2010b). …”

Interactions between voluntary and involuntary attention modulate the quality and temporal dynamics of visual processing

“…They have shown that exogenous and endogenous attention not only enhance perceptual sensitivity but also modulate the rate of information accrual, allowing discriminability to reach asymptote faster at attended relative to unattended locations. Exogenous and endogenous attention lead to similar behavioral consequences in most instances (Herrmann, Montaser-Kouhsari, Carrasco, & Heeger, 2010; Montagna, Pestilli, & Carrasco, 2009) but not all (Barbot, Landy, & Carrasco, 2011; Yeshurun, Montagna, & Carrasco, 2008). In short, covert spatial attention not only modulates how we process incoming stimuli, but actually changes they way in which we subjectively experience the world.…”