Binocular Interactions in Cat Visual Cortical Cells and Coding of Parameters Involved in Static and Dynamic Depth Perception

Abstract

In the representation of the binocular visual field, almost all cortical cells are binocular. This is expressed to a certain extent by the ocular dominance of cortical cells. The binocularity of cortical cells does not necessarily imply that they show binocular interactions. Binocular interactions refer to neuronal responses to binocular stimulation different from the sum of responses to stimulation of each eye in isolation. Binocular interactions are far more important for the understanding of binocular vision than ocular dominance. In addition to binocular fusion and rivalry, binocular interactions underly the coding of a special class of visual parameters referred to as disparities i.e. differences between the eyes with respect to a given attribute. These disparities are important to binocular vision in two ways. On the one hand they have to be discarded by the visual system so as to allow fusion of the two slightly different retinal images to one cyclopean image. On the other hand they have to be used by the system in order to extract the information they contain on the third dimension of space. Students of stereopsis have mainly investigated the influence of position and orientation disparities, both cues for static depth perception (i.e. perception in depth of stationary objects). With respect to dynamic depth perception (i.e. the perception of objects moving in depth) both binocular cues (difference in velocity and direction between both eyes) and monocular cues (changing size) have been investigated. The binocularity of cortical cells will be described first.