Abstract
A detailed model of how the visual cortex represents slanted and curved surfaces in three-dimensional space is presented. These 3-D representations depend crucially on non-classical receptive field interactions with both intracortical and intercortical feedback playing major roles. Neurophysiological experiments have disclosed the existence of cells that are sensitive to angles (Pasupathy and Connor, 00), and to disparity-gradients (Hinkle and Connor, 01). The model shows how such cells are organized within the laminar circuits of cortical areas V1 and V2, notably layers 6, 4, 3B and 2/3A, for representing slanted and curved surfaces. The model can explain slant aftereffects, contrast displays that involve disparity gradients, and variants of neon color spreading in 3-D. The model also explains how 2-D pictures that implicitly represent slanted and curved 3-D surfaces can generate 3-D figure-ground percepts. Apart from binocular disparities, various monocular cues, such as occlusion, contrast, relative size, and angles, give rise to compelling 3-D percepts. Many of these monocular cues by themselves are ambiguous. For example a specific angle in an image can be associated with different surface slants. The model explains how non-classical receptive field interactions within the laminar circuits of visual cortex can contextually disambiguate the classical receptive field responses to individually ambiguous cues. The model shows how these interactions explain data such as volume completion images (Tse, 99) and Necker cube multi-stable percepts (Kawabata, 86).
Sources of support: Supported in part by AFOSR F49620-98-1-0108, AFOSR F49620-01-1-0397, NSF IIS-97-20333, ONR N0001495-1-0409, ONR N00014-95-1-0657, and ONR N00014-01-1-0624.