Burr David, Ross John
Istituto di Neuroscienze del CNR, Pisa 56100, Italy.
Vision Res. 2006 Mar;46(6-7):1139-44. doi: 10.1016/j.visres.2005.09.018. Epub 2005 Oct 25.
Glass patterns--randomly positioned coherently orientated dipoles--create a strong sensation of oriented spatial structure. On the other hand, coherently oriented dipoles comprising dots of opposite polarity ("anti-Glass" patterns) have no distinct spatial structure and are very hard to distinguish from random noise. Although anti-Glass patterns have no obvious spatial structure themselves, their presence can destroy the structure created by Glass patterns. We measured the strength of this effect for both static and dynamic Glass patterns, and showed that anti-Glass patterns can raise thresholds for Glass patterns by a factor of 2-4, increasing with density. The dependence on density suggests that the interactions occur at a local level. When the Glass and anti-Glass dipoles were confined to alternate strips (in translational and circular Glass patterns), the detrimental effect occurred for stripe widths less than about 1.5 degrees, but had little effect for larger stripe widths, reinforcing the suggestion that the interaction occurred over a limited spatial extent. The extent of spatial interaction was much less than that for spatial summation of these patterns, at least 30 degrees under matched experimental conditions. The results suggest two stages of analysis for Glass patterns, an early stage of limited spatial extent where orientation is extracted, and a later stage that sums these orientation signals.
格拉斯图案——随机分布但方向一致的偶极子——会产生强烈的定向空间结构感。另一方面，由极性相反的点组成的方向一致的偶极子（“反格拉斯”图案）没有明显的空间结构，很难与随机噪声区分开来。尽管反格拉斯图案本身没有明显的空间结构，但它们的存在会破坏格拉斯图案所形成的结构。我们测量了静态和动态格拉斯图案这种效应的强度，结果表明反格拉斯图案能使格拉斯图案的阈值提高2至4倍，且随密度增加。对密度的依赖性表明这种相互作用发生在局部层面。当格拉斯和反格拉斯偶极子被限制在交替的条带中（平移和圆形格拉斯图案）时，条纹宽度小于约1.5度时会产生有害影响，但条纹宽度较大时影响很小，这进一步表明相互作用发生在有限的空间范围内。空间相互作用的范围远小于这些图案的空间总和，在匹配的实验条件下至少相差30度。结果表明格拉斯图案的分析有两个阶段，一个是空间范围有限的早期阶段，用于提取方向，另一个是后期阶段，对这些方向信号进行求和。
