Relative localization in the human fovea: radial-tangential anisotropy.
A distinction is drawn between two intrinsic directions within a simple spatial configuration. The line joining two elements is the radial direction and orthogonal to it is the tangential direction. Separation and bisection discrimination and just-detectable differences in line length are examples of radial thresholds. Vernier and alignment detection are tangential thresholds. Neural processing along these two intrinsic directions differs. There is a strong 'oblique effect' for tangential thresholds and virtually none for radial thresholds. Flank interaction impairs tangential but not radial thresholds.
Westheimer
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Division of Neurobiology, 565 Life Sciences Addition, University of California, Berkeley, CA 94720-3200, USA. gwest@socrates.berkeley.edu
D005584:Fovea Centralis / Q000502:physiology*; D006801:Humans; D014785:Vision, Ocular / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*