Evidence for surface-based processing of binocular disparity.
It is convenient to think of an object's location as a point within a Cartesian framework; the x axis corresponds to right and left, the y axis to up and down, and the z axis to forward or backward. When an observer is looking straight ahead, binocular disparities provide information about distance along the z axis from the fixation plane. In this coordinate system, changes in disparity are treated as independent of changes in location along the orthogonal x and y axes. Does the human visual system use this three-dimensional coordinate system, or does it specify feature location in a coordinate frame determined by other nearby visible features? Here we show that the sensitivity of the human stereo system is determined by the distance of points with respect to a local reference plane, rather than by the distance along the z axis with respect to the fixation plane. There is a distinct advantage to using a local frame of reference for specifying location. It obviates the need to construct a complex three-dimensional space in either eye-centered or head-centered coordinates that must be updated with every shift of the eyes and head.
Glennerster
Andrew
A
University Laboratory of Physiology, Parks Road, OX1 3PT, Oxford, United Kingdom. ag@physiol.ox.ac.uk
McKee
Suzanne P
SP
Birch
Martin D
MD
D055592:Biophysical Phenomena; D001703:Biophysics; D003867:Depth Perception / Q000502:physiology; D006801:Humans; D008954:Models, Biological; D015357:Vision Disparity / Q000502:physiology*