Three-dimensional visual information processing in the parietal cortex

为了阐明涉及三维（3D）表面方向感知的神经机制，我们使用Go/No-go型延迟匹配样本（DMTS）任务训练猴子从双眼视差线索中区分表面的三维方向，并检查了表面定向选择（SOS）神经元的特性。我们记录了日本猕猴（Macaca fuscata）顶内沟外侧库尾侧部分（CIP区）的SOS神经元。我们使用立体立体图（SFS）和无透视提示的随机点立体图（RDS）的方形板测试SOS神经元；几乎所有被测神经元对无视角提示的SFS和/或RDS表现出表面取向选择性。这些结果表明，在没有视角线索的RDS中，表现出表面取向调整的神经元是根据双眼视差梯度来计算表面取向的，而在没有视角线索的SFS中，表现出表面取向调整的神经元可能主要是根据双眼视差沿等高线的梯度来表示表面取向的。此外，我们还研究了线性视角线索对SOS神经元反应的影响。神经元只使用实体图像和透视线索进行测试。超过一半的被测神经元对视角和视差线索都敏感，但少数神经元只对视角线索敏感。被试对立体图形的反应强度在单独透视提示下弱于视差提示，说明两种线索对表面取向知觉的影响是综合的，但视差提示的作用是主导的。我们还测试了纹理渐变的效果。许多神经元对纹理梯度敏感，超过一半的神经元对视差梯度敏感，表明CIP区域纹理梯度信息与视差梯度信息相融合。这些结果表明，CIP区域的单目深度线索与视差线索相结合，建立了一个独立于信息源的表面方向的广义表示。最后，使用功能性磁共振成像（fMRI）检查皮质活动，受试者在没有任何双眼视差提示的情况下，根据阴影区分表面中央部分是突出还是凹陷，并显示右侧顶叶内区被激活。这一结果强烈表明，顶叶内区在感知物体表面的三维结构中起着重要作用，即使仅基于单眼深度线索而没有双眼视差线索。综上所述，CIP区域的SOS神经元可能通过整合多种深度线索对视差信号进行更高阶的表面知觉加工。少

In order to elucidate the neural mechanisms involved in the perception of the three-dimensional (3D) orientation of a surface, we trained monkeys to discriminate the 3D orientation of a surface from binocular disparity cues using a Go/No-go type delayed-matching-to-sample (DMTS) task and examined the properties of the surface-orientation-selective (SOS) neurons. We recorded SOS neurons from the caudal part of the lateral bank of the intraparietal sulcus (area CIP) of Japanese monkeys (Macaca fuscata). We tested SOS neurons using the square plate of a solid figure stereogram (SFS) and random-dot stereogram (RDS) without perspective cues ; almost all of tested neurons showed surface orientation selectivity for the SFS and/or the RDS without perspective cues. These results suggest that neurons which show surface orientation tuning for the RDS without perspective cues compute surface orientation from the gradient of the binocular disparity and neurons which show surface orientation tuning … More for the SFS without perspective cues may represent surface orientation primarily from the gradient of the binocular disparity along the contours. Furthermore, we investigated the effects of linear perspective cues on the response of SOS neurons. Neurons were tested using the solid figure with perspective cues alone. More than half of tested neurons were sensitive to both perspective and disparity cues, but a few were sensitive to perspective cues alone. The response magnitude to the solid figure with perspective cues alone was weaker than that with disparity cues, suggesting the integration of both cues for the perception of surface orientation, however, the dominance of disparity cues. We also tested the effects of texture gradient. Many neurons were sensitive to the texture gradient, and more than half of them were also sensitive to the disparity gradient, suggesting that texture gradient information is integrated with disparity gradient in area CIP.These results suggest that the monocular depth cues are integrated with the disparity cues in area CIP to build up a generalized representation of surface orientation independent of the source of information. Finally, cortical activities were examined using functional magnetic resonance imaging (fMRI) while subjects discriminated whether the central part of the surface was protruded or recessed based on shading without any binocular disparity cues and the right intraparietal area was shown to be activated. This result strongly suggests that the intraparietal area plays an important role in perception of a 3D structure of a surface, even when based only on monocular depth cues without binocular disparity cues.In conclusion, the SOS neurons in the area CIP are likely to operate higher order processing of disparity signals for surface perception by integrating the several kinds of depth cues. Less