Orientation selectivity of the human visual system as a function of retinal eccentricity and visual hemifield.

An adaptation method was used to determine the specificity of orientation-selective channels in the human visual system at different retinal eccentricities (up to 16 deg) in both hemifields of each eye. For a vertical test grating, the elevation in contrast threshold produced by adapting to a high-contrast grating of the same spatial frequency but variable orientation was equated with the contrast levels of a vertical adapting grating that produced equivalent effects (equivalent-contrast transformation). This enabled comparisons to be made between the orientation tuning of the aftereffect at different retinal loci. For the spatial frequency employed (3 cycles deg-1), no systematic change in orientation selectivity was found as a function of either retinal eccentricity or the hemifield (and hence the cerebral hemisphere) stimulated.