The Impact of Density and Ratio on Object-Ensemble Representation in Human Anterior-Medial Ventral Visual Cortex
The Impact of Density and Ratio on Object-Ensemble Representation in Human Anterior-Medial Ventral Visual Cortex
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DOI：
10.1093/cercor/bhu145
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发表时间：
2015-11-01
期刊：
影响因子：
3.7
通讯作者：
Xu, Yaoda
中科院分区：
文献类型：
--
作者：
Cant, Jonathan S.;Xu, Yaoda
行为研究表明，观察者可以从多个对象的集合中提取汇总统计数据。我们最近发现，前内侧腹侧视觉皮层的一个区域，在很大程度上与场景敏感的海马旁位置区（PPA）重叠，参与对象集成表示。在这里，我们研究了编码的合奏密度在这个大脑区域使用fMRI适应。在实验1中，我们通过改变物体之间的间距来改变密度，并发现PPA对这种密度变化不敏感。因此，密度可能不会被编码在PPA中，这可能是因为对象间距没有被感知为固有的整体属性。在实验2中，我们通过改变组成系综的2种类型的对象的比率来改变相对密度，并观察到PPA对这种比率变化的显着敏感性。虽然在实验2中示出了彩色的合奏，实验3表明，对物体比率变化的敏感性主要不是由颜色比率的变化驱动的。因此，虽然前内侧腹侧视觉皮层对密度（物体间距）的变化不敏感，但它确实在整体中编码相对密度（物体比率）。因此，该区域中的对象集合处理可以取决于诸如对象比率的高级视觉信息，而不是诸如间隔/空间频率的低级信息。
Behavioral research has demonstrated that observers can extract summary statistics from ensembles of multiple objects. We recently showed that a region of anterior-medial ventral visual cortex, overlapping largely with the scene-sensitive parahippocampal place area (PPA), participates in object-ensemble representation. Here we investigated the encoding of ensemble density in this brain region using fMRI-adaptation. In Experiment 1, we varied density by changing the spacing between objects and found no sensitivity in PPA to such density changes. Thus, density may not be encoded in PPA, possibly because object spacing is not perceived as an intrinsic ensemble property. In Experiment 2, we varied relative density by changing the ratio of 2 types of objects comprising an ensemble, and observed significant sensitivity in PPA to such ratio change. Although colorful ensembles were shown in Experiment 2, Experiment 3 demonstrated that sensitivity to object ratio change was not driven mainly by a change in the ratio of colors. Thus, while anterior-medial ventral visual cortex is insensitive to density (object spacing) changes, it does code relative density (object ratio) within an ensemble. Object-ensemble processing in this region may thus depend on high-level visual information, such as object ratio, rather than low-level information, such as spacing/spatial frequency.