Center for Perceptual Systems, University of Texas at Austin, Austin, United States; Department of Psychology, University of Texas at Austin, Austin, United States; Center for Theoretical and Computational Neuroscience, Austin, United States; Department of Neuroscience, University of Texas at Austin, Austin, United States; Department of Neurosurgery, Rutgers University, New Brunswick, United States
Yuzhi Chen
Center for Perceptual Systems, University of Texas at Austin, Austin, United States; Department of Psychology, University of Texas at Austin, Austin, United States; Center for Theoretical and Computational Neuroscience, Austin, United States; Department of Neuroscience, University of Texas at Austin, Austin, United States
Wilson S Geisler
Center for Perceptual Systems, University of Texas at Austin, Austin, United States; Department of Psychology, University of Texas at Austin, Austin, United States; Center for Theoretical and Computational Neuroscience, Austin, United States
Center for Perceptual Systems, University of Texas at Austin, Austin, United States; Department of Psychology, University of Texas at Austin, Austin, United States; Center for Theoretical and Computational Neuroscience, Austin, United States; Department of Neuroscience, University of Texas at Austin, Austin, United States
Visual detection is a fundamental natural task. Detection becomes more challenging as the similarity between the target and the background in which it is embedded increases, a phenomenon termed ‘similarity masking’. To test the hypothesis that V1 contributes to similarity masking, we used voltage sensitive dye imaging (VSDI) to measure V1 population responses while macaque monkeys performed a detection task under varying levels of target-background similarity. Paradoxically, we find that during an initial transient phase, V1 responses to the target are enhanced, rather than suppressed, by target-background similarity. This effect reverses in the second phase of the response, so that in this phase V1 signals are positively correlated with the behavioral effect of similarity. Finally, we show that a simple model with delayed divisive normalization can qualitatively account for our findings. Overall, our results support the hypothesis that a nonlinear gain control mechanism in V1 contributes to perceptual similarity masking.
