Grant: Discovery Grants Program - Individual

1. Because the eyes are separated, the images of objects away from where the eyes are converged differ in horizontal location in the two retinas. These horizontal disparities are detected locally to indicate the 3-D structure of scenes. Images also differ vertically, depending on the eccenticity and absolute distance of objects. We showed that vertical disparities are averaged over wide areas rather than processed locally. Vertical disparities modify depth created by horizontal disparities. I plan to determine whether all horizontal disparities are modified or only those that define a specific depth plane. The results will indicate for the first time how the two types of disparity are combined in 3-D perception.   2. Objects at different distances in the midline introduce three complications. 1) Their images fall in opposite halves of the brain, so that disparity detection requires information to be conveyed over nerves that connect the hemispheres (corpus callosum). 2) The images are topologically  disordered. 3) The images have a steep spatial gradient of disparity. These three factors complicate detection of disparity and depth for such objects. I will dissociate the three factors to reveal how the visual system copes with each difficulty in isolation.