September 2011
Volume 11, Issue 11
Free
Vision Sciences Society Annual Meeting Abstract  |   September 2011
Feature-based enhancement of visual stimuli at task-irrelevant locations
Author Affiliations
  • David Painter
    Queensland Brain Institute, University of Queensland, St Lucia, Queensland 4072, Australia
  • Susan Travis
    Queensland Brain Institute, University of Queensland, St Lucia, Queensland 4072, Australia
    School of Psychology, University of Queensland, St Lucia, Queensland 4072, Australia
  • Paul Dux
    School of Psychology, University of Queensland, St Lucia, Queensland 4072, Australia
  • Jason Mattingley
    Queensland Brain Institute, University of Queensland, St Lucia, Queensland 4072, Australia
    School of Psychology, University of Queensland, St Lucia, Queensland 4072, Australia
Journal of Vision September 2011, Vol.11, 133. doi:10.1167/11.11.133
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      David Painter, Susan Travis, Paul Dux, Jason Mattingley; Feature-based enhancement of visual stimuli at task-irrelevant locations. Journal of Vision 2011;11(11):133. doi: 10.1167/11.11.133.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

The visual system selects inputs for extended processing on the basis of their features or locations. To date, considerable research has investigated the mechanisms underlying both featural and spatial selection, yet the extent to which these processes interact remains unknown. Here, we tested whether feature-based attention acts independently of spatial location by examining whether a featural set applies at locations that are completely task-irrelevant (i.e., outside the focus of spatial attention). In blocks of trials, observers monitored central vision for target letters in a cued color (red or green) that appeared within multi-letter arrays. Within each array, the target was defined either by a unique color (unique feature search) or by a combination of color and shape (conjunction search). The letter arrays were surrounded by colored checkerboards in peripheral vision that were always task-irrelevant and could therefore be ignored throughout the experiment. We used ‘frequency tagging’ in which flickering stimuli produce cortical oscillations at the flicker frequency, detectable at the scalp via electroencephalography (EEG). This approach allowed us to distinguish neural responses evoked by the task-relevant central stream from activity related to the task-irrelevant peripheral checkerboards. The checkerboard stimuli contained interleaved elements of three different colors: those that matched the target color, those that matched the distractor color, and those of a third, neutral color. During unique feature search, the magnitude of checkerboard-evoked brain oscillations was independent of the search color. During conjunction search, however, we found that checkerboard elements matching the target color evoked enhanced cortical oscillations relative to those associated with distractor or neutral colors. These results provide strong evidence that feature-based attention applies globally across the visual field, irrespective of the current focus of spatial attention.

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