Introduction

In understanding visual processing, it is important to establish not only the local response properties for elements in the visual field, but also the scope of neural interactions when two or more elements are present at different locations in the field. Since the original report by Polat and Sagi (1993), the presence of interactions in the two-dimensional (2D) field has become well established by threshold measures (Polat and Tyler, 1999; Chen and Tyler, 1999, 2001, 2008; Levi et al., 2002). A large array of other studies have also looked at such interactions with suprathreshold paradigms (e.g., Field et al., 1993; Hess et al., 2003). The basic story from both kinds of studies is that there are facilitatory effects between oriented elements that are collinear with an oriented test target and inhibitory effects elsewhere in the 2D spatial domain of interaction (although the detectability of a contrast increment on a Gabor pedestal also reveals strong collinear masking effects).

The present work extends this question to the third dimension of visual space as specified by binocular disparity, asking both what interactions are present through the disparity dimension and how these interactions vary with the spatial location of the disparate targets. Answering these questions is basic to the understanding of the visual processing of the 3D environment in which we find ourselves.