Symmetry as a cue to object and scene representations in human visual cortex

人类视觉系统必须将到达视网膜的2D图像转换为我们可以用来感知世界并与世界互动的视觉场景的3D表示。视觉对称性是这一过程的一个重要线索，已被发现在视觉反应的大脑区域引起强烈的反应。大多数关于视觉感知中对称性的研究都使用了有限范围的刺激参数：(1)反射而不是其他类型的对称性；(2)单一图像位置的对称轴；(3)正面平行图像平面上的对称性。拟议的研究计划建立在最新进展的基础上，以解决这些限制，并加强我们对对称性的理解，将其作为物体和场景感知的线索。项目1将探索对称类型、平铺和倾斜是如何调节对对称的敏感性的。我之前的工作表明，视觉大脑区域对反射以外的对称性很敏感，对称在平面上平铺的纹理会产生强大的视觉反应，但尚不清楚平铺和对称类型如何调节大脑区域的活动。这种倾斜操作的动机是这样一个事实，尽管对称性通常发生在自然界中，但在自然观察下，对称的图像平面投影到视网膜上的情况很少发生。因此，人们很自然地会问，视觉系统能在多大程度上克服当世界上的对称性在视网膜上产生“扭曲”的投射时产生的扭曲。为了解释这样一种假设，即这些操作以不同的方式驱动人类视觉皮质中不同的对称敏感子网络，我将使用大脑成像方法以高时间和空间精度测量对对称反应的幅度、时间和皮质来源。这个项目将提供视觉系统中对称性调谐的更完整的特征，并有可能将不同的文学分支联系起来。项目2将解决这样的假设，即对对称的敏感性是婴幼儿在视觉环境中暴露于对称的学习的结果，因此人类视觉皮质对对称的反应应该在早期发育过程中发生变化。我将通过比较婴儿和成年人的对称性反应来测试这一点。据我们所知，这将是第一个研究婴儿或幼儿对称性知觉的大脑成像研究。这项研究将揭示早期视觉发育中可能存在的对对称性的敏感性，并提供关于对称性的编码如何随着暴露在自然世界中而变化的线索。这项研究计划解决了对称性和3D对象和场景感知文献之间的一个重要差距，使用控制良好的刺激结合最先进的大脑成像技术。这些发现有可能加深我们对对称性在自然视觉中的作用的理解，并为视觉神经科学和计算机视觉的相关研究提供信息。

The human visual system must convert the 2D image arriving at the retina into a 3D representation of the visual scene that we can use to perceive and interact with the world. Visual symmetry is an important cue to this process and has been found to elicit strong responses in visually responsive brain areas. Most studies of symmetry in the context of visual perception have used a limited range of stimulus parameters: (1) Reflection rather than other types of symmetry, (2) symmetry axes at a single image location, and (3) symmetries in the fronto-parallel image plane. The proposed research program builds on recent advances in order to address these limitations and enhance our understanding of symmetry as a cue to object and scene perception. Project 1 will explore how sensitivity to symmetry is modulated by symmetry type, tiling and skew. My prior work shows that visual brain areas are sensitive to symmetries other than reflection, and that textures in which symmetries are tiled across the plane produce robust visual responses, but it is unclear how tiling and symmetry type modulate activity across brain areas. The skew manipulation is motivated by the fact that although symmetries commonly occur in the natural world, symmetrical image-plane projections onto the retina rarely occur under natural viewing. It is thus natural to ask to what extent the visual system can overcome distortions introduced when symmetries in the world produce "skewed" projections onto the retina. To address the hypothesis that these manipulations differentially drive distinct symmetry-sensitive sub-networks in human visual cortex, I will use brain imaging methods to measure the amplitude, timing and cortical sources of responses to symmetry with high temporal and spatial precision. This project will provide a more complete characterization of symmetry tuning in the visual system and has the potential to connect distinct branches of the literature. Project 2 will address the hypothesis that sensitivity to symmetry is the result of learning as infants and young children are exposed to symmetries in their visual environment, and that responses to symmetry in human visual cortex should therefore change over early development. I will test this by comparing symmetry responses in infants and adults. To our knowledge, this will be the first brain imaging study to investigate symmetry perception in infants or young children. This study will reveal any sensitivity to symmetry that may exist in early visual development, and provide cues as to how encoding of symmetry changes with exposure to the natural world. This research program addresses an important gap between the symmetry and 3D object and scene perception literatures using well-controlled stimuli combined with state-of-the-art brain imaging techniques. The findings have the potential to deepen our understanding of the role of symmetry in natural vision, and inform related research in visual neuroscience and computer vision.