Bredfeldt Christine E, Cumming Bruce G
Laboratory of Sensorimotor Research, National Eye Institute, Bethesda, Maryland 20892, USA.
J Neurosci. 2006 Jul 19;26(29):7581-96. doi: 10.1523/JNEUROSCI.5308-05.2006.
It has been shown recently that neurons in V2 respond selectively to the edges of figures defined only by disparity (cyclopean edges). These responses are orientation selective, often preferring similar orientations for cyclopean and luminance contours, suggesting that they may support a cue-invariant representation of contours. Here, we investigate the extent to which processing of purely local visual information (in the vicinity of the receptive field) might explain such results, using the most impoverished stimulus possible containing a cyclopean edge (a circular patch of random dots divided into two regions by a single edge). Many V2 cells responded better to the cyclopean edge than to uniform disparities, and most of these were at least broadly selective for the orientation of the cyclopean edge. Two characteristics argue against a cue-invariant contour representation: (1) the cyclopean edge response was frequently abolished by small changes to the component disparities; and (2) although V2 cells frequently responded to both signs of a cyclopean edge (defined by which side of the edge is in front), they did so at different edge locations. These characteristics are consistent with a simple feedforward scheme in which V2 neurons receive inputs from several V1 subunits with different disparity selectivity. We also found a correlation between the preferred orientations for cyclopean edges and contrast stimuli, suggesting that this feedforward wiring is not random. These characteristics suggest that V2 responses to cyclopean edges may be useful in supporting a cue-invariant contour representation higher in the visual pathway.
最近的研究表明，V2区的神经元对仅由视差定义的图形边缘（独眼巨人边缘）有选择性反应。这些反应具有方向选择性，通常对独眼巨人轮廓和亮度轮廓偏好相似的方向，这表明它们可能支持轮廓的线索不变表示。在这里，我们使用包含独眼巨人边缘的最简化刺激（一个由单个边缘分成两个区域的随机点圆形斑块），研究纯粹局部视觉信息（在感受野附近）的处理在多大程度上可以解释这些结果。许多V2细胞对独眼巨人边缘的反应比对均匀视差的反应更好，并且其中大多数至少对独眼巨人边缘的方向具有广泛的选择性。有两个特征与线索不变的轮廓表示相悖：（1）独眼巨人边缘反应经常因组成视差的微小变化而消除；（2）虽然V2细胞经常对独眼巨人边缘的两个方向（由边缘的哪一侧在前定义）都有反应，但它们在不同的边缘位置这样做。这些特征与一种简单的前馈方案一致，即V2神经元从几个具有不同视差选择性的V1亚单位接收输入。我们还发现独眼巨人边缘的偏好方向与对比度刺激之间存在相关性，这表明这种前馈布线不是随机的。这些特征表明，V2对独眼巨人边缘的反应可能有助于支持视觉通路中更高层次的线索不变轮廓表示。
