Lorenceau J, Boucart M
Laboratoire de Psychologie Expérimentale, Université Paris V, CNRS, Paris, France.
Vision Res. 1995 Aug;35(16):2303-14. doi: 10.1016/0042-6989(94)00322-d.
We studied how the visual system integrates locally ambiguous velocities into global unambiguous coherent motion in the presence or absence of a textured background. Line drawings of complex figures were presented through invisible (i.e. same luminance and hue as the background) circular apertures such that only straight line segments were visible. These figures were either presented against a uniform background or embedded in static textures made of similar line segments in such a way that figures cannot be detected if they remain static. Under our experimental conditions, the figures translated clockwise or counterclockwise along a circular path and observers were required to discriminate the global direction of motion. Because of the aperture problem, a single moving segment cannot disambiguate the global direction of the figures and integration across multiple line segments is therefore necessary to perform the task. We found that with figures at high contrast, the presence of a texture enhanced direction discrimination, while direction discrimination of figures at low contrast was impaired by the presence of the texture. These paradoxical effects of a static texture were further tested by manipulating the relative contrast between figures and texture, the motion onset asynchrony (the delay between stimulus onset and motion onset or MOA), the density, the orientation and the distribution of texture elements. The effects of the texture, either facilitation or suppression, increase with texture contrast. Accuracy improves with MOA and decreases with texture density. In general, at high figure contrast, accuracy is better whenever referents are present in the image. We suggest that facilitation by the texture at high figure contrast is accounted for by reduced salience of segmentation cues such as line terminators and increased accuracy of local velocity measurements. On the other hand, decreased performance at low figure contrast may reflect lateral suppression of the responses to motion signals by the texture.
我们研究了视觉系统如何在有或没有纹理背景的情况下，将局部模糊的速度整合为全局明确的连贯运动。复杂图形的线条图通过不可见的（即与背景具有相同亮度和色调）圆形孔径呈现，使得只有直线段可见。这些图形要么呈现于均匀背景上，要么以这样一种方式嵌入由相似线段组成的静态纹理中：如果图形保持静止，则无法被检测到。在我们的实验条件下，图形沿圆形路径顺时针或逆时针平移，观察者被要求辨别运动的全局方向。由于孔径问题，单个移动线段无法明确图形的全局方向，因此需要跨多个线段进行整合才能完成任务。我们发现，对于高对比度的图形，纹理的存在增强了方向辨别能力，而低对比度图形的方向辨别能力则因纹理的存在而受损。通过操纵图形与纹理之间的相对对比度、运动起始异步性（刺激开始与运动开始之间的延迟或MOA）、纹理元素的密度、方向和分布，进一步测试了静态纹理的这些矛盾效应。纹理的促进或抑制作用随纹理对比度增加。准确性随MOA提高而提高，随纹理密度降低而降低。一般来说，在高图形对比度下，只要图像中有参照对象，准确性就更好。我们认为，高图形对比度下纹理的促进作用是由于诸如线条终止点等分割线索的显著性降低以及局部速度测量准确性的提高。另一方面，低图形对比度下性能的下降可能反映了纹理对运动信号响应的侧向抑制。
