Role of area V4 in the perception of partially occluded objects

描述(申请人提供)：人类视觉系统快速、准确、看似毫不费力地识别部分遮挡的物体。我实验室研究的长期目标是确定灵长类视觉系统是如何实现这一点的。先前的研究已经证明，到达我们眼睛的视觉信息是沿着腹侧的多阶段“形状处理”途径进行处理的。我们将研究V4区，这一通路的中间阶段，在部分闭塞过程中的作用。当三维世界将二维图像投射到视网膜上时，距离观察者较近的对象会部分或完全遮挡较远的对象。这会在视网膜图像中造成两种类型的失真。首先，由于被遮挡对象和被遮挡对象的边界轮廓意外地并置，部分遮挡会产生“偶然”的轮廓特征。其次，被遮挡的物体的部分缺失，甚至可能在视网膜图像中出现碎片。为了在部分遮挡的情况下准确地识别被遮挡的物体，视觉系统需要剔除偶然的轮廓特征，然后通过动态地补齐丢失的轮廓来缝合碎片部分。心理学和理论证据表明，在视觉加工的早期阶段，对遮挡和遮挡轮廓线(类T形交叉点)的图像特征的分析是遮挡加工的基础，但其神经机制尚不清楚。损伤研究和神经生理学研究的证据表明，V4区可能发挥重要作用。一个相互竞争的假说提出，遮挡是由于在加工的最高阶段，如下颞叶皮质中，从物体的碎片化部分中对物体进行稳健识别的结果。这两个假设对V4区的反应模式做出了截然不同的预测。我们将对清醒的灵长类动物进行V4神经元的单细胞记录，这些灵长类动物正在执行注视和行为任务。在目标1中，我们将调查V4响应是否支持对真实和意外轮廓特征的差异处理。在目标2中，我们将调查V4区的动态完成信号是在准确识别部分遮挡对象之前还是之后出现的。这些实验的结果将决定上述哪一种假设在灵长类动物的大脑中得到支持。它还将识别有助于推断部分闭塞的V4神经机制。视觉失认症是枕颞部通路的一种功能障碍，物体识别能力受损。拟议中的实验结果将是我们对作为物体识别基础的大脑计算的理解的重大进步，并将使我们更接近于设计出缓解和治疗这种大脑疾病的策略。与公共健康相关的物体识别是人脑的一种基本能力，对于我们与他人的互动以及所有复杂的行为都是至关重要的。这种基本的大脑功能在视觉失认中受损，这是一种枕颞部通路的功能障碍。拟议中的实验结果将是我们对作为物体识别基础的大脑计算的理解的重大进步，并将使我们更接近于设计出缓解和治疗这种大脑疾病的策略。

Description (provided by applicant): The human visual system rapidly, accurately, and seemingly effortlessly, recognizes objects that are partially occluded. The long-term goal of research in my laboratory is to determine how this is achieved by the primate visual system. Previous research has demonstrated that visual information that reaches our eyes is processed along the multi-stage ventral "shape processing" pathway. We will investigate the contributions of area V4, an intermediate stage in this pathway, to the processing of partial occlusion. When the three-dimensional world casts a two-dimensional image on the retina, objects that are closer to the viewer partially or completely occlude objects that are farther away. This causes two types of distortions in the retinal image. First, partial occlusions produce "accidental" contour features due to the accidental juxtaposition of the bounding contours of the occluded and occluding objects. Second, parts of the occluded object are missing and may even be fragmented in the retinal image. To accurately recognize the occluded object despite partial occlusion, the visual system needs to discount the accidental contour features and then sew together the fragmented parts by amodally completing the missing contours. Psychological and theoretical evidence suggests that analysis of image features at the intersecting junctions of the occluded and occluding contours (T-like junctions) in the early stages of visual processing underlies processing of occlusion but the neural mechanisms are unknown. Evidence from lesion studies and neurophysiological studies suggest that area V4 is likely to play an important role. A competing hypothesis proposes that occlusion is inferred as a result of robust recognition of objects from their fragmented parts in the highest stages of processing such as inferotemporal cortex. The two hypotheses make distinct predictions about the patterns of responses in area V4. We will conduct single cell recordings of V4 neurons in awake primates performing fixation and behavioral tasks. In aim 1, we will investigate if V4 responses support differential processing of real and accidental contour features. In aim 2, we will investigate if amodal completion signals in area V4 appear before or after accurate recognition of the partially occluded object. Results from these experiments will determine which of the above hypotheses is supported in the primate brain. It will also identify V4 neural mechanisms that contribute to inference about partial occlusion. Object recognition is impaired in visual agnosia, a dysfunction of the occipitotemporal pathway. Results from the proposed experiments will constitute a major advance in our understanding of the brain computations that underlie object recognition and will bring us closer to devising strategies to alleviate and treat this brain disorder. PUBLIC HEALTH RELEVANCE Object recognition is a fundamental capacity of the human brain essential for our interaction with others and for all complex behavior in general. This fundamental brain function is impaired in visual agnosia, a dysfunction of the occipitotemporal pathway. Results from the proposed experiments will constitute a major advance in our understanding of the brain computations that underlie object recognition and will bring us closer to devising strategies to alleviate and treat this brain disorder.