title: How vernier acuity depends on contrast.
abstract: Vernier acuity was measured by finding the just discriminable offset for an edge separating fields of different luminances. The contrast of this stimulus is easily specified by the formula c = (Lstim - Lsur)(Lstim + Lsur). Vernier thresholds are about 4-5 sec of arc for contrasts 0.22 and higher, but increase exponetially with decreasing contrast. By comparison, the presence of the stimulus could be detected at a contrast of 0.016. The possible role of the magnocellular and parvocellular pathways in carrying the input signals to the fine localization process is discussed.
authors.affiliation: Department of Physiology and Anatomy, University of California, Berkeley 94720.
authors.forename: C
authors.initials: C
authors.lastname: Wehrhahn
authors.forename: G
authors.initials: G
authors.lastname: Westheimer
mesh_terms: D005556:Form Perception / Q000502:physiology*; D006801:Humans; D010364:Pattern Recognition, Visual / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology*