Pettet M W, McKee S P, Grzywacz N M
Smith-Kettlewell Eye Research Institute, San Francisco, CA 94115, USA.
Vision Res. 1998 Mar;38(6):865-79. doi: 10.1016/s0042-6989(97)00238-1.
Contour detection may be mediated by lateral interactions between neighboring cortical neurons whose receptive fields have collinear axes of preferred orientation. This hypothesis was tested in psychophysical experiments and computer simulations using a contour detection task in which observers searched for groups of Gabor patches that followed spatially extended contour paths embedded in noise consisting of several hundred Gabor patches with random positions and orientations. The orientation-selective units in the simulated neural network were linked by facilitatory interconnections whose strength depended on the geometry (distance, curvature, change in curvature) of smooth curves connecting the orientation axes of units in a pairwise fashion. Psychophysical detection performance was much higher for contour signal groups that followed closed rather than open-ended paths. However, just two sudden changes in orientation of neighboring Gabor patch elements in closed-path contours reduced detection performance to the same levels obtained with open-ended contours. These psychophysical data agreed with the results of the neural network simulations. Furthermore, the simulations also accounted for previous findings that removal of a single Gabor patch element from a closed-path contour group significantly degraded detection performance. We conclude that closure alone is not sufficient to enhance the visibility of a contour. However, if a closed contour meets certain geometric constraints, then lateral interactions based on these constraints can generate facilitation that reverberates around the closed path, thereby enhancing the contour's visibility.
轮廓检测可能由相邻皮质神经元之间的侧向相互作用介导，这些神经元的感受野具有共线的偏好取向轴。该假设在心理物理学实验和计算机模拟中得到了检验，实验使用了轮廓检测任务，观察者在其中搜索一组Gabor斑块，这些斑块沿着嵌入在由数百个具有随机位置和取向的Gabor斑块组成的噪声中的空间扩展轮廓路径排列。模拟神经网络中的方向选择性单元通过促进性互连相连，其强度取决于以成对方式连接单元方向轴的平滑曲线的几何形状（距离、曲率、曲率变化）。对于遵循闭合路径而非开放式路径的轮廓信号组，心理物理学检测性能要高得多。然而，在闭合路径轮廓中，相邻Gabor斑块元素的方向仅发生两次突然变化，就会使检测性能降低到与开放式轮廓相同的水平。这些心理物理学数据与神经网络模拟的结果一致。此外，模拟还解释了先前的发现，即从闭合路径轮廓组中移除单个Gabor斑块元素会显著降低检测性能。我们得出结论，仅闭合不足以提高轮廓的可见性。然而，如果闭合轮廓满足某些几何约束，那么基于这些约束的侧向相互作用可以产生在闭合路径周围回荡的促进作用，从而提高轮廓的可见性。
