Spatial attention alters visual appearance

Abstract

Does attention alter appearance? This critical issue, debated for over a century, remains unsettled. From psychophysical evidence that covert attention affects early vision-it enhances contrast sensitivity and spatial resolution-and from neurophysiological evidence that attention increases the neuronal contrast sensitivity (contrast gain), one could infer that attention changes stimulus appearance. Surprisingly, few studies have directly investigated this issue. Here we developed a psychophysical method to directly assess the phenomenological correlates of attention in humans. We show that attention alters appearance; it boosts the apparent stimulus contrast. These behavioral results are consistent with neurophysiological findings suggesting that attention changes the strength of a stimulus by increasing its 'effective contrast' or salience. At any given moment, our visual system is confronted with far more information than it can process effectively. The high energy cost of neuronal activity involved in cortical computation severely limits our capacity to process this information 1. Visual attention serves as a mediating mechanism, enabling us to selectively grant priority of processing to certain aspects of the visual scene. One means of granting priority is to direct one's gaze towards the relevant location. However, many situations call for one to attend to an area in the periphery without actually directing gaze toward it. For example, when driving it is generally best to keep your eyes on the road ahead while covertly monitoring the periphery for cars, pedestrians and potential road hazards. The impact of covert attention 2 on visual performance is well-documented across a range of perceptual tasks, such as visual search 3-6 , letter identification 7,8 , contrast sensitivity 9-12 and spatial resolution 13-16. Several studies that used single-cell recording 17-22 , event-related potentials 23,24 and functional magnetic resonance imaging (fMRI) 25-27 indicate that attentional modulation occurs as early as striate and extrastriate visual cortex. Transient attention, a type of covert attention, is the stimulus-driven, reflexive capture of attention by an abrupt, salient peripheral cue 3-6,8-10,13-16,28-30. For example, a ball rolling out into the street instantly grabs one's transient attention, improving discriminability 8-16 and speeding information processing 3,4 , enabling one to make a better and faster judgment of whether to swerve away. Explanations of how attention improves performance range from claims that the deployment of attention affects processing at the decisional level 9-11,31,32 , to claims that attention actually enhances perceptual sensitivity 2-6,8-16. At the perceptual level, two prominent models have been proposed: signal enhancement

Paying attention to attention in depression

“…More recently, cognitive psychological studies have characterized the particular ways, in which attention can influence perception, from low-level visual features to high-level perceptual judgments (for review see ref. 43 ). For example, a large body of research has demonstrated that both automatic attention and voluntary attention to particular visual stimuli increases perception of both contrast and color saturation 44,45 .…”

What is visible across the visual field?

“…If the main model reflects the enhanced response state of an attended region, we can implement the withdrawal of attention by reducing Rmax. Reducing this parameter would mirror the kinds of reductions seen in neural contrast response functions (Buracas & Boynton, 2007;Gandhi et al, 1999;Luck et al, 1997), and would also reduce contrast sensitivity and perceived contrast judgments (assuming that perceived contrast is strongly linked to contrast response magnitude) in similar ways to what is observed psychophysically (Carrasco et al, 2000(Carrasco et al, , 2004Carrasco & Barbot, 2019;John M. Foley & Schwarz, 1998;Huang & Dobkins, 2005).…”

Sensitivity measures of visuospatial attention

“…Journal of Vision, 19(12):17, 1-13, https://doi.org/10.1167/19.12.17. Braun, 1999), and alters appearance (Carrasco & Barbot, 2019).…”