Ailene Chan

The blind spot is an area on the retina that lacks photoreceptors, thus no visual information is encoded. Yet, we can maintain the sense of a seamless visual field owing to perceptual filling-in. Traditionally viewed as a surface interpolation mechanism, filling-in has been studied predominantly under unimodal conditions. However, there are limits to this process; the brain cannot always reconstruct all surfaces. Multisensory processing may bolster the process of perceptual filling-in to occur even with complex and dynamic perceptual stimuli. In this study, we employed the Audiovisual (AV) Rabbit Illusion to investigate how auditory stimuli influence visual filling-in at the blind spot. Our findings confirmed that auditory cues can induce the perception of an illusory flash within the blind spot, indicating that the brain leverages multimodal information to enrich visual scenes. This suggests that perceptual filling-in is not merely unimodal surface interpolation but a cross-modally integrated spatial representation and therefore more similar to other visual field locations than previously hypothesized. Furthermore, for blind spot filling-in to occur, visual stimuli do not need to be spatially contiguous, they simply need to be crossmodally associated (or grouped), which supports a higher-level sensory processing in filling-in than previously understood.Competing Interest StatementThe authors have declared no competing interest.

A significant proportion of the human neurotypical population exhibits some degree of sensory eye dominance (SED), referring to the brain’s preferential processing of one eye’s input versus another. The neural substrates underlying this functional imbalance are not well known. Here, we investigated the relationship between visual white matter tract properties and SED in the human neurotypical population. Observers’ performance on two commonly used dichoptic tasks were used to index SED, along with performance on a third task to address a functional implication of binocular imbalance: stereovision. We show that diffusivity metrics of the optic radiations (ORs) well predict behavioral SED metrics. We found no relationship between SED and stereosensitivity. Our data suggest that SED is not simply reflected by gray matter structural and functional alterations, as often suggested, but relates, at least in part to the microstructural properties of thalamocortical white matter.