Invariance of surface color representations across illuminant changes in the human cortex
Invariance of surface color representations across illuminant changes in the human cortex
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DOI：
10.1016/j.neuroimage.2017.06.079
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发表时间：
2017-09-01
期刊：
影响因子：
5.7
通讯作者：
Bartels, Andreas
中科院分区：
文献类型：
--
作者：
Bannert, Michael M.;Bartels, Andreas
色觉的一个核心问题是，从给定表面到达眼睛的光会根据照明而发生显着变化。尽管如此，我们的颜色感知，大脑对表面反射率的估计，仍然非常稳定。这种现象被称为颜色恒常性。在这里，我们研究了人类大脑区域代表表面颜色的方式是不变的照明变化。我们使用物理逼真的渲染方法来显示自然而抽象的3D场景，这些场景在三种不同的光源下显示。场景嵌入，在不同的条件下，表面不同的表面颜色（即。e.在其反射特性方面）。我们使用多变量功能磁共振成像模式分析探测神经编码的表面反射和照明，分别。虽然所有的视觉区域编码的表面颜色时，在相同的光源下观看，我们发现，只有在V1和V4阿尔法表面颜色表示是不变的照明变化。沿着视觉层次，存在从V1到V4 α的梯度，以逐渐编码表面颜色而不是照明。最后，刺激操作对个人行为的颜色恒常性指数的影响与神经编码的照明在HV4。这为等效光源模型提供了神经证据。我们的研究结果提供了一个原则性的表征颜色恒常性机制在整个视觉层次，并展示了互补的贡献，在早期和后期的处理阶段。
A central problem in color vision is that the light reaching the eye from a given surface can vary dramatically depending on the illumination. Despite this, our color percept, the brain's estimate of surface reflectance, remains remarkably stable. This phenomenon is called color constancy. Here we investigated which human brain regions represent surface color in a way that is invariant with respect to illuminant changes. We used physically realistic rendering methods to display natural yet abstract 3D scenes that were displayed under three distinct illuminants. The scenes embedded, in different conditions, surfaces that differed in their surface color (i. e. in their reflectance property). We used multivariate fMRI pattern analysis to probe neural coding of surface reflectance and illuminant, respectively. While all visual regions encoded surface color when viewed under the same illuminant, we found that only in V1 and V4 alpha surface color representations were invariant to illumination changes. Along the visual hierarchy there was a gradient from V1 to V4 alpha to increasingly encode surface color rather than illumination. Finally, effects of a stimulus manipulation on individual behavioral color constancy indices correlated with neural encoding of the illuminant in hV4. This provides neural evidence for the Equivalent Illuminant Model. Our results provide a principled characterization of color constancy mechanisms across the visual hierarchy, and demonstrate complementary contributions in early and late processing stages.