Analysis of 3D visual information processing in the parietal association cortex

近年来的神经生理学研究表明，顶叶皮层可以划分为若干个子区域，这些区域在空间视觉的信息加工中起着不同的作用。立体视觉是基于投射在两个视网膜上的图像来感知视觉世界深度的能力。双眼差异是构建3D视觉世界的关键线索，然而，单眼深度线索，如纹理、阴影和线性视角也非常重要。Marr （Marr 1982）在他的视觉理论中假设，物体三维表征的视觉信息处理的一个重要步骤是描述可见表面的几何形状，特别是表面的方向和曲率。心理物理学研究已经证明了几种不同的视差线索和单眼线索对表面取向的表征。这些不同类型的深度线索的综合处理是建立表面方向的神经表征所必需的。研究了警觉猴顶叶内沟外侧库尾侧部分（CIP区）的表面定向选择（SOS）神经元的特性，发现了一组对双眼视差信号和单眼深度信号敏感的神经元。我们还发现CIP区域的神经元对由Koenderink公式定义的曲面有响应。这些神经元可能有助于视觉世界中物体的三维特征的表征。

Recent neurophysiological studies have shown that the parietal cortex can be classified into sub-regions and that those regions play different roles in information processing for spatial vision. Stereopsis is the ability to perceive depth of the visual world based on images projected on the two retinae. Binocular disparities are crucial cues for building a 3D representation of the visual world, however, monocular depth cues, such as texture, shading, and linear perspective are also very important for that. Marr (Marr 1982) postulated in his theory of vision that an important step in visual information processing for 3D representation of an object is the description of the geometry of the visible surface, especially that of the surface orientation and curvature. Several kinds of disparity cues and monocular cues for the representation of surface orientation have been demonstrated from psychophysical studies. Integrative processing of these different types of depth cues is necessary to build a neural representation of the surface orientation. We examined the properties of surface orientation selective (SOS) neurons in the caudal part of the lateral bank of the intraparietal sulcus (area CIP) of alert monkeys, and identified a group of neurons which are sensitive to binocular disparity cues and also monocular depth cues. We also found that the neurons in the area CIP responded to curved surface defined by the Koenderink's formula. These neurons may contribute to the representation of the 3D feature of objects in the visual world.