Feature Selectivity in the Far Periphery

Humans can successfully recognize objects in the far periphery (30-80° of visual angle) despite limited acuity (Boucart et al., 2013; 2016; Baldwin et al., 2016; Rosenholtz, 2016). This ability may be supported by the prostriata, a brain region activated by stimuli at 60° periphery (Mikellidou et al., 2017), with retinotopic organization, and projections to the thalamus (Kurzawaski et al., 2020), similar to visual cortex. Notably, orientation selectivity generally serves as a building block for object recognition by critically supporting edge detection. However, it is unclear whether the same mechanisms are present in far peripheral sensory populations (e.g., akin to those in prostriata). Therefore we sought to determine if orientation selectivity was possible up to 90° eccentricity. Circular patches of moving or static square wave gratings were presented at 30, 60, and 90° at either cardinal (90° or 180°) or oblique (45° or 135°) orientations. Subjects (N = 30) reported whether motion was present followed by the orientation of the stimulus. Performance was above chance on motion trials across all eccentricities, and across all orientations presented below 90° eccentricity. In the orientation discrimination task, subjects performed better on cardinal orientation trials compared to oblique with the magnitude of the difference increasing with eccentricity. In a second experiment, we scaled stimuli to account for early visual cortical magnification (N = 31). This time, performance was above chance on all conditions, and interactions from Experiment 1 were no longer significant. However, we still observed a significant main effect of eccentricity and orientation. Our results suggest that despite degraded acuity in the far periphery, representations of visual orientation involved in edge detection are still maintained up to 90° periphery. These representations possibly serve as a building block for object recognition in the far periphery.