Non-uniform contextual interactions in the visual cortex place fundamental limits on spatial vision

A common assumption is that contextual integration in the primary visual cortex (V1) is spatially uniform. However, perceptual phenomena such as visual crowding reveal non-uniform interactions, with flankers at specific geometries exerting stronger effects. To resolve this discrepancy, we investigated how flanker geometry impacted the representation of a target stimulus in the laminar microcircuits of V1. Our study indicates that flanker location differentially impairs stimulus representation in excitatory neurons in the superficial and input layers of V1 through tuned suppression and untuned facilitation of orientation responses. Mechanistically, this effect can be explained by asymmetrical spatial kernels in a normalization model of cortical activity. Strikingly, these non-uniform modulations of neural representation mirror perceptual anisotropies. These results demonstrate that the non-uniform spatial integration of information in the earliest stages of cortical processing places a fundamental limit on spatial vision.