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

Abstract

Attention is often regarded as a mechanism by which attended objects become perceptually more salient, akin to increasing their contrast. We demonstrate that attention is better described as a mechanism by which task relevant information impacts on ongoing processing, while excluding task irrelevant information. We asked subjects to judge the orientation of a target relative to a reference, in a single and dual task setting. The target orientation percept was systematically influenced by the presentation of prior spatio-temporal context. We found that the sign of the context influence depended on target contrast, but its strength depended on the level of attention devoted to the task. Thus the effects of attention and contrast were fundamentally different; contrast influenced the sign of contextual interactions, while attention suppressed these interactions irrespective of their sign.

Additive Effects of Attention and Stimulus Contrast in Primary Visual Cortex

“…The idea that the effects of attention are similar to an increase in stimulus contrast is not undisputed, however, as other psychophysical studies reported that attention has only little influence on perceived contrast ( Prinzmetal et al 1997 ; Liston and Stone 2008 ; Schneider and Komlos 2008 ), whereas another study demonstrated that attention and contrast can even have opposite effects ( Roberts and Thiele 2008a , 2008b ). Furthermore, observers are well able to direct their attention to low-contrast image regions and even give them priority if they are task relevant ( Pashler et al 2004 ; Einhauser et al 2008 ).…”

How Simultaneous is the Perception of Binocular Depth and Rivalry in Plaid Stimuli?

“…Subjects have a very limited ability to detect changes that happen after attention has been directed away from an object and before attention returns to that object (Wolfe et al 2006 ). Selective attention in the concurrent task conditions is also related to a mechanism by which task-relevant information impacts on ongoing processing, while task-irrelevant information is excluded (Roberts and Thiele 2008 ).…”

“…The effects of attention have often been compared to the effects of increasing stimulus contrast, in that objects or features that are attended to are more salient (Boynton 2009 ; Roberts and Thiele 2008 ). In neural models, the effects of attention on neuronal responses have been characterized in further detail as reflecting a contrast gain, baseline shift or multiplicative gain (Boynton 2009 ).…”

Attention – oscillations and neuropharmacology

“…, 1998; Zenger et al. , 2000; Roberts & Thiele, 2008) or served as a noise‐exclusion mechanism when stimuli had to be detected in noisy environments (Lu & Dosher, 1998; Dosher & Lu, 2000; Lu et al. , 2002).…”

“…A variety of human psychophysical studies have indeed demonstrated that selective spatial attention can ensure that task-irrelevant information (information surrounding a target) has a reduced influence on perception. In these studies attention served to reduce the influence of behaviourally irrelevant contextual stimuli ( Ito et al , 1998 ; Zenger et al , 2000 ; Roberts & Thiele, 2008 ) or served as a noise-exclusion mechanism when stimuli had to be detected in noisy environments ( Lu & Dosher, 1998 ; Dosher & Lu, 2000 ; Lu et al , 2002 ). In line with the above prediction, Roberts et al (2007) reported that attention reduced the spatial integration of parafoveal cells in V1 and the underlying changes were mediated by a change in the spatial summation area ( Roberts et al , 2007 ).…”