Curvature detection in the visual field and a possible physiological correlate.

Discrimination of curvature in nearly straight stimuli was measured for twelve stimulus orientations, corresponding to the hours of the clock, at eleven positions in the visual field of human observers. Displacements below the diameter of a photoreceptor can be detected foveally. In the periphery of the visual field, stimuli oriented towards the fovea yield best results. This anisotropy of orientation discrimination seems not to have an optical cause. It has a close correlation both to the structure and functional properties of cat ganglion cells, to the organization of receptive fields in area 17 and to the geometry of ocular dominance stripes.