MECHANISMS OF STEREOSCOPIC PROCESSING - STEREOATTENTION AND SURFACE PERCEPTION IN-DEPTH RECONSTRUCTION

Consideration of the range of phenomena from studies of human stereops is suggests that a five-stage model is required to provide a complete account of the processes involved, within which any stereoattention me chanism must operate. The information from the disparity field of the optical projections to the two eyes (stage 1) goes to a set of paralle l Keplerian arrays of disparity detectors, each array selective for a different spatiotemporal property of the visual images (stage 2). Glob al interactions produce a cyclopean depth image that is cleaned of the spurious ghost images in the Keplerian arrays (stage 3) and that may then be processed for its (hypercyclopean) form elements (stage 4). Fi nally, there must be a stage of integration of the stereoscopic depth cues with monocular and kinesthetic depth cues to form the overall map of perceived distance (stage 5). The fact that multiple cyclopean sur faces may be perceived as transparent implies that the stereoscopic sy stem is not limited by a singular-surface constraint. However, it is u nclear whether multiple surfaces can be seen simultaneously or whether only one surface is seen at a time by a selective-attention process, with the others perceived as a purely inchoate (qualitative) depth imp ression. New experiments on cueing of ambiguous stereocorrugations by singular flat planes suggest that selective stereoattention is a power ful mechanism. In fact, the results show that attention can be focused not just in horopteral planes but in a variety of depth configuration s. Moreover, this attention focus may act as a tracking mechanism to a llow perception of smooth cyclopean stereomotion, which has a frequenc y response up to similar to 5 Hz (in contrast to the similar to 15 Hz limit for detecting planar disparity shifts as jerky appearance and di sappearance effects). Finally, the spatial limits of stereosurface rec onstruction are explored with cyclopean targets to show some interesti ng asymmetries of the surface-wrapping process that may represent obje ct-oriented constraints on depth reconstruction.