Department of Psychology, Cognitive Neuroscience Group, University of Amsterdam Amsterdam, Netherlands.
Front Comput Neurosci. 2012 Jun 8;6:34. doi: 10.3389/fncom.2012.00034. eCollection 2012.
Texture may provide important clues for real world object and scene perception. To be reliable, these clues should ideally be invariant to common viewing variations such as changes in illumination and orientation. In a large image database of natural materials, we found textures with low-level contrast statistics that varied substantially under viewing variations, as well as textures that remained relatively constant. This led us to ask whether textures with constant contrast statistics give rise to more invariant representations compared to other textures. To test this, we selected natural texture images with either high (HV) or low (LV) variance in contrast statistics and presented these to human observers. In two distinct behavioral categorization paradigms, participants more often judged HV textures as "different" compared to LV textures, showing that textures with constant contrast statistics are perceived as being more invariant. In a separate electroencephalogram (EEG) experiment, evoked responses to single texture images (single-image ERPs) were collected. The results show that differences in contrast statistics correlated with both early and late differences in occipital ERP amplitude between individual images. Importantly, ERP differences between images of HV textures were mainly driven by illumination angle, which was not the case for LV images: there, differences were completely driven by texture membership. These converging neural and behavioral results imply that some natural textures are surprisingly invariant to illumination changes and that low-level contrast statistics are diagnostic of the extent of this invariance.
纹理可以为真实世界的物体和场景感知提供重要线索。为了可靠起见，这些线索在理想情况下应该对常见的观察变化（例如照明和方向的变化）保持不变。在一个大型的自然材料图像数据库中，我们发现具有低水平对比度统计的纹理在观察变化下会发生很大变化，而有些纹理则保持相对不变。这使我们不禁要问，具有恒定对比度统计的纹理是否会产生比其他纹理更不变的表示。为了验证这一点，我们选择了具有高（HV）或低（LV）对比度统计方差的自然纹理图像，并将其呈现给人类观察者。在两个不同的行为分类范式中，参与者更经常将 HV 纹理判断为“不同”，而不是 LV 纹理，这表明具有恒定对比度统计的纹理被感知为更不变。在一个单独的脑电图（EEG）实验中，我们采集了对单个纹理图像（单图像 ERP）的诱发反应。结果表明，对比度统计差异与个体图像之间枕叶 ERP 幅度的早期和晚期差异均相关。重要的是，HV 纹理图像之间的 ERP 差异主要由照明角度驱动，而 LV 图像则并非如此：在 LV 图像中，差异完全由纹理成员驱动。这些神经和行为学结果的一致性表明，某些自然纹理对光照变化具有惊人的不变性，并且低水平对比度统计可用于诊断这种不变性的程度。
