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Franco Pestilli, Jerry Viera, Marisa Carrasco; On the interaction between covert attention and contrast adaptation. Journal of Vision 2006;6(6):604. doi: 10.1167/6.6.604.
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© ARVO (1962-2015); The Authors (2016-present)
Background: Transient (exogenous) attention automatically enhances contrast sensitivity at valid-cue locations and impairs it at invalid-cue locations, compared to a neutral condition (Pestilli & Carrasco, 2005). Contrast adaptation reduces contrast sensitivity to stimuli similar to the adapter. Here we investigated whether attention and adaptation act on similar neural mechanisms when processing contrast signals.
Methods: We assessed accuracy in a 2AFC orientation-discrimination task for Gabors at 8 contrast levels (1–100%). There were 2 adaptation conditions and 3 attentional conditions. Adaptation: Observers adapted for 70s to either two 100%- or 0%-contrast vertical Gabors (counterphase modulated at 7.5Hz) in opposite hemifields along the horizontal meridian. Attention: Before each of the 20 test trials an uninformative precue directed transient attention to one of the Gabors. A response cue appeared after stimuli offset indicating the target Gabor. On valid-cue trials the response-cue pointed to the precued Gabor. On invalid-cue trials it pointed to the other Gabor. In the remaining trials the precue was presented at fixation and the response cue indicated either stimulus with equal probability (neutral-cue).
Results: Adaptation decreased contrast sensitivity for all cue conditions. Transient attention increased contrast sensitivity at valid-cue locations and decreased it at invalid-cue locations in both adaptation conditions. The effects of transient attention were similar in magnitude in both adaptation conditions. Attention counteracted contrast adaptation: sensitivity for the adapted stimulus following a valid-cue was similar to that for the non-adapted stimulus following a neutral-cue. These results suggest that attention and adaptation tap into similar mechanisms.
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