Distinct effects of contour smoothness and observer bias on visual persistence

Abstract

Stable object perception relies on persistent yet temporary neural representations under constantly fluctuating stimulus conditions. The mechanisms by which such representations are formed and maintained are not fully understood but presumably involve interplay between early and higher-tier visual cortical mechanisms. Here we show that the visual persistence of highly camouflaged contours is based on the persistent operation of mechanisms sensitive to contour smoothness, which we dissociate from individual differences in response bias. Our results are consistent with existing models of visual cortical processing that predict persistent contour perception, which until now has not been studied systematically in relation to contour integration. We argue that the surprisingly long duration of contour persistence is in part due to response bias but that the strong modulatory effects of contour smoothness on persistence indicate sustained reverberation of a contour binding mechanism in visual cortex, a unique type of short-term visual memory that supports perceptual continuity.