Role of area V4 in the perception of partially occluded objects

描述（由申请人提供）：人类视觉系统快速，准确，似乎毫不费力地识别被部分遮挡的物体。我实验室的长期研究目标是确定灵长类动物的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多阶段的腹侧“形状加工”通路进行加工的。我们将研究V4区的贡献，在这一途径的中间阶段，部分闭塞的处理。当三维世界在视网膜上投射二维图像时，离观察者较近的物体部分或完全遮挡了较远的物体。这导致视网膜图像中的两种类型的失真。首先，部分遮挡产生“意外”的轮廓特征，由于被遮挡和遮挡对象的边界轮廓的意外并置。第二，被遮挡对象的部分丢失，甚至可能在视网膜图像中被分割。为了准确地识别被遮挡的物体，尽管部分遮挡，视觉系统需要折扣偶然的轮廓特征，然后通过非模态地完成缺失的轮廓将碎片部分缝合在一起。心理学和理论证据表明，在视觉处理的早期阶段，在被遮挡和遮挡轮廓的交叉路口（T形路口）的图像特征分析是遮挡处理的基础，但神经机制尚不清楚。来自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。一个竞争性假设提出，遮挡是在颞下皮质等最高处理阶段从对象的碎片部分进行鲁棒识别的结果。这两个假说对V4区的反应模式做出了不同的预测。我们将在清醒的灵长类动物中进行V4神经元的单细胞记录，执行固定和行为任务。在目标1中，我们将研究V4响应是否支持真实的和偶然的轮廓特征的差分处理。在目标2中，我们将研究区域V4中的非模态完成信号是否出现在部分遮挡对象的准确识别之前或之后。这些实验的结果将决定灵长类动物的大脑支持上述假设中的哪一个。它还将确定V4神经机制，有助于推断部分闭塞。视觉失认症是一种枕颞通路的功能障碍，其目标识别受损。这些实验的结果将使我们对物体识别背后的大脑计算的理解取得重大进展，并使我们更接近于制定缓解和治疗这种大脑疾病的策略。物体识别是人类大脑的一种基本能力，对于我们与他人的互动以及所有复杂的行为都至关重要。这种基本的大脑功能在视觉失认症中受损，这是一种枕颞通路的功能障碍。这些实验的结果将使我们对物体识别背后的大脑计算的理解取得重大进展，并使我们更接近于制定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.