Non-uniform signal pooling across the foveola

Object recognition is impacted by visual crowding. This phenomenon, attributed to cortical pooling, is generally studied in the periphery. Crowding mechanisms in the foveola-the 1° retinal region with highest resolution-remain unclear due to difficulties in controlling for optical factors and incessant fixational eye motion. Using high-resolution retinal imaging and retinal-contingent stimulus rendering to overcome these limitations, we demonstrated that the critical spacing at the preferred retinal locus approximates a single cone's diameter. However, just 0.25° away, mislocalization errors start to occur and the extent of crowding exceeds cone spacing. These results reveal that cortical pooling mechanisms may play a greater role with increasing foveolar eccentricity and point to a possible cortical magnification gradient effect within the central fovea.