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Elizabeth Cutrone, David J. Heeger, Marisa Carrasco; A normalization model of attention predicts enhanced contrast appearance. Journal of Vision 2013;13(9):241. doi: https://doi.org/10.1167/13.9.241.
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Goal. Attention to a stimulus increases neural responses and increases perceived contrast. Here we investigated how perceived contrast is linked to changes in neural activity by fitting psychophysical measurements of contrast appearance with a computational model of visual cortical responses. Method. Observers viewed two tilted Gabor stimuli (test and standard) on each trial and reported the orientation of the stimulus that appeared to have higher contrast (2-AFC). Exogenous attention was manipulated via a pre-cue, either at fixation (neutral) or near the location of either stimulus. We measured the point of subjective equality (PSE), the contrast at which observers chose the test stimulus with probability 0.5, for six standards of different contrasts. We used the normalization model of attention (Reynolds and Heeger, 2009) to predict neural responses corresponding to the different pre-cues (neutral, cue-test, cue-standard), then fit the model to the psychophysical PSEs. Results. Attention significantly boosted perceived contrast: the PSE was higher when the standard was cued compared to the neutral cue, and lower when the test stimulus was cued. In the best-fitting model, the pre-cue caused an increase in the baseline activity of simulated neurons with corresponding receptive fields. Conclusions. The effect of attention on perceived contrast is mediated by an additive increase in neural responses. This baseline increase is qualitatively consistent with fMRI measurements of visual cortical responses to attended stimuli. Reynolds JH & Heeger DJ, Neuron, 61:168-185, 2009.
Meeting abstract presented at VSS 2013
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