Korea Brain Research Institute.
Harvard University.
J Cogn Neurosci. 2017 Oct;29(10):1778-1789. doi: 10.1162/jocn_a_01156. Epub 2017 Jun 9.
A host of recent studies have reported robust representations of visual object information in the human parietal cortex, similar to those found in ventral visual cortex. In ventral visual cortex, both monkey neurophysiology and human fMRI studies showed that the neural representation of a pair of unrelated objects can be approximated by the averaged neural representation of the constituent objects shown in isolation. In this study, we examined whether such a linear relationship between objects exists for object representations in the human parietal cortex. Using fMRI and multivoxel pattern analysis, we examined object representations in human inferior and superior intraparietal sulcus, two parietal regions previously implicated in visual object selection and encoding, respectively. We also examined responses from the lateral occipital region, a ventral object processing area. We obtained fMRI response patterns to object pairs and their constituent objects shown in isolation while participants viewed these objects and performed a 1-back repetition detection task. By measuring fMRI response pattern correlations, we found that all three brain regions contained representations for both single object and object pairs. In the lateral occipital region, the representation for a pair of objects could be reliably approximated by the average representation of its constituent objects shown in isolation, replicating previous findings in ventral visual cortex. Such a simple linear relationship, however, was not observed in either parietal region examined. Nevertheless, when we equated the amount of task information present by examining responses from two pairs of objects, we found that representations for the average of two object pairs were indistinguishable in both parietal regions from the average of another two object pairs containing the same four component objects but with a different pairing of the objects (i.e., the average of AB and CD vs. that of AD and CB). Thus, when task information was held consistent, the same linear relationship may govern how multiple independent objects are represented in the human parietal cortex as it does in ventral visual cortex. These findings show that object and task representations coexist in the human parietal cortex and characterize one significant difference of how visual information may be represented in ventral visual and parietal regions.
大量近期研究报告称，在人类顶叶皮层中存在与腹侧视觉皮层相似的视觉对象信息的强大表示。在腹侧视觉皮层中，猴子神经生理学和人类 fMRI 研究都表明，一对不相关对象的神经表示可以通过单独显示的组成对象的平均神经表示来近似。在这项研究中，我们研究了人类顶叶皮层中的对象表示是否存在这种对象之间的线性关系。我们使用 fMRI 和多体素模式分析，分别检查了人类下顶内沟和上顶内沟两个顶叶区域以及外侧枕叶区域的对象表示，这两个区域先前都与视觉对象选择和编码有关。我们还检查了来自腹侧对象处理区域的反应。当参与者观看这些对象并执行 1 背重复检测任务时，我们获得了对对象对及其组成对象的 fMRI 响应模式。通过测量 fMRI 响应模式相关性，我们发现所有三个脑区都包含单个对象和对象对的表示。在外侧枕叶区域，一对对象的表示可以通过其组成对象的平均表示来可靠地近似，这与腹侧视觉皮层中的先前发现相吻合。然而，在检查的两个顶叶区域中，没有观察到这种简单的线性关系。尽管如此，当我们通过检查两个对象对的反应来平衡存在的任务信息量时，我们发现两个顶叶区域中两个对象对的平均值的表示与另两个包含相同四个组成对象但对象对不同的对象对（即 AB 和 CD 的平均值与 AD 和 CB 的平均值）的表示没有区别。因此，当任务信息量保持一致时，相同的线性关系可能会支配多个独立对象在人类顶叶皮层中的表示方式，就像它在腹侧视觉皮层中一样。这些发现表明，对象和任务表示在人类顶叶皮层中并存，并描述了视觉信息在腹侧视觉和顶叶区域中可能如何表示的一个显著差异。
