Neural correlates of spatiotemporal form intergation

 描述(申请人提供)：传统上，物体知觉的神经关联被识别在形成视觉处理层次的腹侧皮质区域，更深的区域包含具有更大感受野的细胞，这些细胞被认为是抽象(视点、位置和尺度不变)物体表征的基础。这些形式的表象不变性对于静态对象的分类和识别很重要。然而，由于遮挡，自然环境中的大多数对象并不完全可见，并且在它们或我们移动时不是静态的。视觉系统不是表象不变性，而是需要关于对象碎片位置、速度和方向的精确表示，以便将许多跨越时空的碎片集成到感知整体或时空对象中。我们已经进行了两项初步研究，表明背侧区域(V3A、V3B和顶内沟)可能参与动态形式的表征。这就提出了这样一个问题：背侧和腹侧区域的形状信息是相似的还是多余的，或者它们之间是否存在信息的通信和传递，最终导致腹侧区域的不变表示和背侧区域的特定表示。为了识别信号通路(目标1)，受试者将对随着时间逐渐显现的物体(时空物体)或在记录脑电数据的同时立即获得形状信息的物体执行形状识别任务。为了将信号时程与皮质区域联系起来，将收集结构和功能MRI数据，以提高源定位的准确性，并在源定位空间中定义感兴趣区。使用MVPA，我们将解码作为时间函数的每个ROI中的形状标识。如果时空对象表征首先在背部构造 刺激开始后，背侧区域的形状解码可能早于腹侧区域。静态对象标识可能仅在腹侧区域中可被解码。为了证实背侧区域在时空物体表征中的因果作用(目标2)，我们将进行两个实验，在这些实验中，我们对后顶叶皮质(背侧视觉区域)施加经颅直流电刺激(TDC)以破坏动态形式整合。如果背侧区域对于形状信息的整合是必要的，则tdcs应该减少这种形式可以整合的时间，但应该不会对静态形状的感知产生影响。

 DESCRIPTION (provided by applicant): The neural correlates of object perception have been traditionally identified in ventral cortical regions that form a visual processing hierarchy, with deeper regions containing cells with larger receptive fields that are thought to underlie abstract (viewpoint-, position-, and scale-invariant) object representations. These forms of representational invariance are important for the categorization and identification of static objects. However, most objects in our natural environment are not fully visible due to occlusion and are not static as they or as we move. Rather than representational invariance, the visual system requires precise representations about object fragment position, velocity, and orientation in order to integrate many fragments across space and time into perceptual wholes or spatiotemporal objects. We have conducted two preliminary studies that suggest that dorsal regions (V3A, V3B, and the intraparietal sulcus) may be involved in the representation of dynamic forms. This opens the question of whether shape information in dorsal and ventral areas is similar or redundant or whether there is communication and a relaying of information between them that ultimately leads to both invariant representations in ventral areas and specific representations in dorsal areas. To identify the signaling pathway (Aim 1), subjects will perform a shape identification task with objects that are gradually revealed over time (spatiotemporal objects) or with objects whose shape information is available all at once while EEG data is recorded. In order to relate the signaling time-course to cortical areas, structural and functional MRI data will be collected in order to enhance source-localization accuracy and to define ROIs in source-localized space. Using MVPA, we will decode shape identity in each ROI as a function of time. If spatiotemporal object representations are first constructed in dorsal areas and then passed down to ventral ones, shape decoding will be possible earlier after stimulus onset in dorsal areas than in ventral. Static object identity may only be decodable in ventral regions. To confirm the causal role of dorsal areas in spatiotemporal object representation (Aim 2), we will conduct two experiments in which we apply transcranial direct current stimulation (tDCS) to posterior parietal cortex (dorsal visual areas) to disrupt dynamic form integration. If dorsal areas are necessary for integration of shape information over time, tDCS should decrease the time over which such forms can be integrated, but should have no effect on the perception of static shapes.