Spatial contrast sensitivity: effects of peripheral field stimulation during monocular and dichoptic viewing.

This report examines whether a radial grating with a blank 2 deg central aperture viewed with one eye can affect contrast sensitivity for foveally-viewed, counterphasing or stationary, sine-wave gratings seen with the other eye. We find that the moving radial grating preferentially raises the threshold for the low spatial frequencies of the counterphasing but not the stationary foveal stimulus. These results closely parallel recent primate electrophysiological work which suggests that visual stimulation of the peripheral field with a moving radial grating can activate inhibitory corticofugal influences on lateral geniculate neurons. The current data are evaluated in terms of a model which suggests that the peripheral stimulus activates corticofugal mechanisms.