Abstract

Recent estimates of the cortical magnification factor suggest that the area of the cortex devoted to the fovea is considerably higher than previously estimated. Hyperacuity is thought to reflect cortical processing and for Vernier acuity, foveal and peripheral performance has been shown to differ only in terms of the area of cortex devoted to the task (Levi and Klein, 1984). Performance on a different spatial discrimination task, 3-dot bisection, was measured in the fovea and inferior peripheral field at eccentricities of 2.5°, 5°, and 10° of two subjects using a rating scale signal detection paradigm with feedback. By scaling the stimulus size in proportion to recent estimates of the cortical magnification factor at each eccentricity, the functions of s/s over a wide range of separations of reference dots were shown to remain constant in cortical units from 0° to 10°. Further experiments comparing performance for horizontal, vertical, and oblique orientations of the stimulus in different meridians of the visual field revealed performance to be more dependent on the orientation than the location of a stimulus at a given eccentricity. Specifically, position discrimination was better for tangentially than radially oriented stimuli.

© 1985 Optical Society of America