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Franco Pestilli, Barbara Montagna, Justin Gardner, David Heeger, Marisa Carrasco; Spatial attention reduces contrast adaptation. Journal of Vision 2009;9(8):219. doi: 10.1167/9.8.219.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: Directing voluntary covert attention to a location in the visual field enhances contrast sensitivity while adaptation to contrast decreases sensitivity. Does the enhancement in sensitivity brought about by attention interact with adaptation? In particular, might larger decreases in sensitivity with higher contrast adaptation be countered by larger increases in sensitivity with attention?
Methods: We measured contrast discrimination thresholds in a 2IFC task in focal-attention and distributed-attention conditions as a function of the adaptor contrast. Each block of 80 trials started with observers adapting for 70-s to either a blank field or to 4 isoeccentric, 5-Hz counterphase-modulated, 2-cpd gratings. On each trial, following 4-s top-up adaptation, four test gratings of different contrasts were presented at the adaptors' locations in two 600-ms intervals. Only one of the gratings (the target) changed contrast across temporal intervals. Observers reported the interval in which the target grating had higher contrast. We directed observers' attention either to a target location (cued by an arrow at fixation), or to 4 locations (4 arrows), 600-ms before presenting the test gratings. We measured contrast discrimination thresholds both when attention was directed to the target location (focal attention) and when attention was distributed across the four stimuli (distributed attention). Adaptor contrast varied from 0 to 100%.
Results: Discrimination thresholds increased with adaptor contrast. Thresholds were lower for focal- than distributed-attention for all adaptor contrasts, indicating that attention improved contrast discrimination. The effect of attention increased as a function of adaptor contrast, such that thresholds in the focal-attention condition approached those found without adaptation.
Conclusion: Attention counteracts the effect of adaptation; it restores visibility by bringing the adapted stimulus back to near pre-adaptation visibility levels. This is consistent with the idea that the effect of attention and adaptation might rely on common neural mechanisms.
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