Lateral interactions between targets and flankers in low-level vision depend on attention to the flankers

Abstract

Detection of an oriented visual target can be facilitated by collinear visual flankers. Such lateral interactions are thought to reflect integrative processes in low-level vision. In past studies, the flankers were task-irrelevant, and were typically assumed to be unattended. Here we manipulated attention to the flankers directly, by requiring observers to judge the relative alignment of two flankers while ignoring a second flanker-pair. Under identical stimulus conditions, attended flankers produced typical lateral interactions, but ignored flankers did not. These data show that lateral interactions can depend on attention to the flanking context, revealing the functional consequences of attentional modulation in low-level vision.

Automatic spread of attentional response modulation along Gestalt criteria in primary visual cortex

“…1c, the two relevant central bars had the same orientation and the effect of cueing on the representation of the irrelevant bars cannot be explained by feature-based attention. A previous study 14 showed that a chain of taskrelevant collinear bars induces attentional modulation in V1 whereas the present results show that attention spreads from attended bars to nearby irrelevant bars, but only if they are collinear 15 . The present and previous results, taken together, suggest a common framework for the effects of collinearity and feature similarity.…”

Configuration-Specific Attentional Modulation of Flanker – Target Lateral Interactions

“…Finally, a fresh replication of the original Freeman et al (2001) design with non-rotated single-axis (figures 1a and 1b) and dual-axis stimuli (figures 1c and 1d) was also included, to allow within-subjects comparisons against the novel conditions introduced in this experiment.…”

“…We recently reported psychophysical data suggesting that lateral interactions between a target and collinear flankers might be modified by top^down attention (Freeman et al 2001(Freeman et al , 2003. We used displays that comprised four suprathreshold flankers (figures 1c and 1d) surrounding a central near-threshold target (ie two pairs of flankers, rather than the usual single pair; see figures 1a and 1b).…”

“…If true, we should find that the attentional effects always ride on top' of any fundamental effects of flanker collinearity on target visibility, with residual facilitation from collinear flankers even when they are task-irrelevant. Uncertainty over this issue remains because in our previous attentional studies (Freeman et al 2001(Freeman et al , 2003 we only manipulated whether collinear flankers were attended for the secondary task or were instead ignored, not whether collinearity was physically present or absent in the dual-axis (ie four-flanker) stimulus. In the present study, our modified (collinearity disrupted) stimuli (see figures 1e^1h) should make it possible to measure directly the impact of ignored collinear versus noncollinear flankers on target detection (see experiment 1 below).…”

Attention and contrast differently affect contextual integration in an orientation discrimination task

“…Local context influences the ability to detect or discriminate visual targets (Ito et al 1998;Ito and Gilbert 1999;Zenger et al 2000;Freeman et al 2001;Albright and Stoner 2002;Schwartz et al 2007;Thiele 2007). Certain contextual configurations result in pop-out which enhance stimulus detection (Nothdurft 1993;Wang et al 1994;Braun and Julesz 1998), while others result in crowding and impair stimulus detection (Pelli et al 2004).…”