Spatial covert attention increases contrast sensitivity across the CSF: Support for signal enhancement

Marisa Carrasco, Cigdem Penpeci-Talgar, Miguel Eckstein

Research output: Contribution to journalArticlepeer-review


This study is the first to report the benefits of spatial covert attention on contrast sensitivity in a wide range of spatial frequencies when a target alone was presented in the absence of a local post-mask. We used a peripheral precue (a small circle indicating the target location) to explore the effects of covert spatial attention on contrast sensitivity as assessed by orientation discrimination (Experiments 1-4), detection (Experiments 2 and 3) and localization (Experiment 3) tasks. In all four experiments the target (a Gabor patch ranging in spatial frequency from 0.5 to 10 cpd) was presented alone in one of eight possible locations equidistant from fixation. Contrast sensitivity was consistently higher for peripherally- than for neutrally-cued trials, even though we eliminated variables (distracters, global masks, local masks, and location uncertainty) that are known to contribute to an external noise reduction explanation of attention. When observers were presented with vertical and horizontal Gabor patches an external noise reduction signal detection model accounted for the cueing benefit in a discrimination task (Experiment 1). However, such a model could not account for this benefit when location uncertainty was reduced, either by: (a) Increasing overall performance level (Experiment 2); (b) increasing stimulus contrast to enable fine discriminations of slightly tilted suprathreshold stimuli (Experiment 3); and (c) presenting a local post-mask (Experiment 4). Given that attentional benefits occurred under conditions that exclude all variables predicted by the external noise reduction model, these results support the signal enhancement model of attention. Copyright (C) 2000 Elsevier Science Ltd.

Original languageEnglish (US)
Pages (from-to)1203-1215
Number of pages13
JournalVision research
Issue number10-12
StatePublished - Jun 2000


  • Attention mechanisms
  • Contrast sensitivity
  • Covert spatial attention
  • Detection
  • External noise reduction
  • Localization
  • Mask
  • Orientation discrimination
  • Peripheral precue
  • Signal enhancement

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems


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