Contributed Session II: Computational modeling of shift in unique yellow for small stimuli.

Abstract

Unique yellow (UY) is largely invariant to L:M cone proportion for spatially-extended stimuli in healthy trichromats. However, a recent adaptive-optics-based study by Boehm et al. reveals that when stimulus size is reduced to a few arcmin, color appearance depends on the local L:M proportion in the patch of the retina on which the stimulus was imaged. We aimed to determine if such findings are consistent with a normative account of visual processing. A series of 3.5 and 10 arcmin stimuli were simulated as isoluminant mixtures of 540 and 680 nm primaries. We modeled sensory encoding under adaptive-optics conditions using the open-source software ISETBio, for simulated retinal cone mosaics with varying local L:M proportions. The resultant cone excitations were decoded using a Bayesian image reconstruction algorithm (Zhang et al., 2022). For the 3.5 arcmin stimuli, as local L:M proportion decreased, the 540 nm component of the reconstructions increased relative to the 680 nm component. This is qualitatively consistent with the experimental observations of Boehm et al. For 10 arcmin stimuli, in contrast, reconstructions were stable across variation in local L:M cone proportion. Notably, reconstructions depend not only on the local L:M cone proportion, but also on the proportion in the immediately surrounding retina, leading to a testable prediction. The computational observations frame the experimental results as a normative consequence of visual processing.