In this article we address the major issue of space vision, how the brain represents the 3D visual world, on the basis of psychophysics, art and neurophysiology. In psychophysics, Gibson found texture gradient and width gradient as well as the gradient of binocular disparity as the major cues of surface orientation in depth. Marr proposed that surface-based representation is the main step to 3D shape representation. In art, the most important method to represent the 3D scene was the linear perspective introduced in Renaissance art and was the most successful in the domestic art of Vermeer. However, Cézanne modified the linear perspective and used surface-based representation in landscape painting. In our neurophysiological study of the monkey parietal cortex, we found surface-orientation-selective (SOS) neurons in the caudal intraparietal (CIP) area. SOS neurons responded selectively to surface orientation in depth presented in random dot stereogram (RDS) with disparity gradient. Many of the SOS neurons also responded selectively to texture gradient and linear perspective, and their responses were enhanced by the combination of these cues. It was concluded that the surface-based representation of the 3D scene might be constructed in the brain by the integration of monocular and binocular cues of depth.
- 3-dimensional world
- Caudal intraparietal (CIP) area
- Surface-orientation-selective neuron