Binocular processes in vernier acuity.

We investigate the role of binocular mechanisms in vernier acuity, using dichoptic variants of spatial-frequency masking and flank-line interference paradigms. The finding that grating masks and flanking lines presented to one eye elevate (worsen) thresholds for detecting vernier offsets presented to the other eye suggests that neural mechanisms mediating vernier acuity receive binocular inputs, thus placing the loci of these mechanisms at postreceptoral sites. The observation that these threshold elevation effects are orientation dependent is consistent with a contribution to vernier acuity from oriented cortical filters.