Cortico-cortical recurrent processes mediate convex figure context effects and cortico-thalamic recurrent processes resolve figure-ground ambiguity

Poster Session F - Tuesday, April 16, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

Mary A Peterson¹ (mapeters@arizona.edu), Elizabeth S Campbell¹; ¹University of Arizona

Previous theory held that image factors like convexity were sufficient for unambiguous figure assignment. However, for unmasked 100-ms displays, we found that the probability of perceiving a figure on the convex side of a border is only slightly higher than chance for two-region displays and increases with the number of display regions. These convexity context effects (CCEs) were observed only when concave regions were homogeneously colored; convex region homogeneity was irrelevant. A Bayesian observer replicated the CCEs by supplementing convexity with a homogeneous background prior and predicted that classic displays with homogeneous convex and concave regions are ambiguous. We examined the temporal evolution of CCEs by presenting pattern masks after 100-ms displays at ISIs of 0, 50, or 100 ms. We expected the masks would add noise to recurrent processing, delaying the outcome of processes in which they play a role. In Exp. 1 participants viewed two- and eight-region displays with homogeneous convex regions. In Exp. 2 they viewed displays with heterogeneous convex regions. CCEs developed over time and emerged earlier in Exp. 2 than Exp. 1 supporting the ambiguity prediction and implicating recurrent processing in CCEs and ambiguity resolution. In Exp. 3, displays and masks were presented to different eyes, thereby delaying subcortical mask interference up to 100ms. Now CCEs emerged at the same time for both display types suggesting that corticofugal recurrent processes resolve the ambiguity of homogeneous convex displays. Our results add to evidence that perceptual organization entails recurrent processing and reveal that corticofugal feedback resolves ambiguity.

Topic Area: PERCEPTION & ACTION: Vision