Topographic Representation of an Occluded Object and the Effects of Spatiotemporal Context in Human Early Visual Areas
Topographic Representation of an Occluded Object and the Effects of Spatiotemporal Context in Human Early Visual Areas
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DOI：
10.1523/jneurosci.1455-12.2013
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发表时间：
2013-10-23
影响因子：
5.3
通讯作者：
Ejima, Yoshimichi
中科院分区：
文献类型：
--
作者：
Ban, Hiroshi;Yamamoto, Hiroki;Ejima, Yoshimichi
遮挡是视觉系统在复杂的自然场景中感知物体形状所面临的主要挑战。虽然行为、神经生理学和建模研究表明，物体的遮挡部分可能在视觉处理的早期阶段完成，但我们对人类大脑如何以及在哪里实现完成知之甚少。在这里，我们提供了功能磁共振成像(FMRI)证据，证明对象的闭塞部分确实在人类V1和V2中以地形图表示。具体来说，我们找到了与V1和V2中不可见物体旋转相对应的地形皮质响应。此外，通过研究被遮挡的目标在精确定义的大脑皮层区域内旋转的神经反应，我们可以将被遮挡部分的地形神经表示与其他类型的神经处理分离，例如物体边缘处理。我们进一步证明，V1中的早期地形表示可以通过在部分遮挡之前获得的对象的整体外观的先验知识来调制。这些发现表明，初级“视觉”区V1不仅有能力处理可见或虚拟(虚幻)感知的物体，而且还能处理物体的“不可见”部分，而不会同时产生视觉感觉，如对这些部分的亮度增强。这一结果还表明，在早期区域，低水平的图像特征和较高的先前认知背景被整合成一个统一的遮挡部分的地形图表征。
Occlusion is a primary challenge facing the visual system in perceiving object shapes in intricate natural scenes. Although behavior, neurophysiological, and modeling studies have shown that occluded portions of objects may be completed at the early stage of visual processing, we have little knowledge on how and where in the human brain the completion is realized. Here, we provide functional magnetic resonance imaging (fMRI) evidence that the occluded portion of an object is indeed represented topographically in human V1 and V2. Specifically, we find the topographic cortical responses corresponding to the invisible object rotation in V1 and V2. Furthermore, by investigating neural responses for the occluded target rotation within precisely defined cortical subregions, we could dissociate the topographic neural representation of the occluded portion from other types of neural processing such as object edge processing. We further demonstrate that the early topographic representation in V1 can be modulated by prior knowledge of a whole appearance of an object obtained before partial occlusion. These findings suggest that primary "visual" area V1 has the ability to process not only visible or virtually (illusorily) perceived objects but also "invisible" portions of objects without concurrent visual sensation such as luminance enhancement to these portions. The results also suggest that low-level image features and higher preceding cognitive context are integrated into a unified topographic representation of occluded portion in early areas.