Spatial pattern summation is phase-insensitive in the fovea but not in the periphery.

We measured the effect of phase coherence on the detectability of a chain of Gabor patches. The stimuli were elongated patterns consisting of 1-8 vertical Gabor patches, aligned vertically and either in phase or 180 deg out of phase from their immediate neighbors. In the fovea, the phase configuration had no effect on detection threshold, suggesting a full-wave rectification operation mediating foveal spatial summation. At 5 deg in the periphery, detection thresholds for the in-phase configuration were lower than those for the alternating-phase configuration, to an extent compatible with a half-wave rectification operation mediating peripheral spatial summation.