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Maria Lev, Uri Polat; Decision criterion is determined by interaction's strength from inside or outside the perceptive field. Journal of Vision 2009;9(8):1033. doi: 10.1167/9.8.1033.
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Signal Detection Theory (SDT) assumes that sensitivity (d') is determined by the strength of the sensory input and the background noise (the signal-to-noise ratio). However, the decision criterion (Cr) is affected by internal properties that are not directly related to the sensory input. It was shown, using two temporal alternative forced choice, that two collinear Gabor patches (GPs) placed outside the perceptive field (PF) increase the d' (facilitation) of the target GP but decrease d' (suppression) when they were placed inside the PF. We recently showed, using a Yes/No paradigm, that d' does not follow the expected collinear facilitation. On the other hand, subjects tend to report targets present in a consistent way with the spatial tuning of collinear facilitation. Here we investigated, using the Yes/No paradigm, whether Cr is modulated by suppression from inside and facilitation from outside the PF. We measured the results for inside the PF for a target-flanker separation of 1.5 (fovea) and 3 wavelengths (periphery, 4 deg), whereas effects outside the PF were tested for 3 (fovea) and 7 wavelengths (periphery, 4 deg). Target-flanker orientation's differences (0, 11, 22.5, 45, 90 degrees) were intermixed. We found that pHit for the collinear is lower than the orthogonal configuration inside the PF and the collinear outside the PF. Cr for collinear configuration is shifted from positive inside the PF to negative outside the PF. Thus, subjects tend to report targets absent for the collinear configuration inside the PF and targets present outside the PF. All together, our results show that Cr is directly modulated by center-surround neural activity, following suppression from the center and facilitation from the surround of the PF. The decision criterion may provide a good estimate for the visual crowding effect that increases with increasing eccentricities.
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