Laboratory of Biological Psychology, University of Leuven (K.U.Leuven), Leuven, Belgium.
Neuroimage. 2011 Jun 1;56(3):1372-81. doi: 10.1016/j.neuroimage.2011.02.079. Epub 2011 Mar 3.
Object knowledge is hierarchical. Several hypotheses have proposed that this property might be reflected in the spatial organization of ventral visual cortex. For example, all exemplars of a category might activate the same patches of cortex, but with a slightly different position of the peak of activation in each patch. According to this view, category selectivity would be organized at a larger spatial scale compared to exemplar selectivity. No empirical evidence for such proposals is available from experiments with human subjects. Here, we compare the relative scale of organization for category and exemplar selectivity in two datasets with two methods: (i) by investigating the previously reported beneficial effect of spatial smoothing of the fMRI data on the reliability of multi-voxel selectivity patterns; and (ii) by comparing the relative weight of lower and higher spatial frequencies in the spatial frequency spectrum of these selectivity patterns. The findings are consistent with the proposal that selectivity for stimulus properties that underlie finer distinctions between objects is organized at a finer scale than selectivity for stimulus properties that differentiate categories. This finding confirms the existence of multiple scales of organization in the ventral visual pathway.
物体知识具有层次性。有几种假设提出，这种特性可能反映在腹侧视觉皮层的空间组织中。例如，一个类别中的所有示例都可能激活相同的皮层斑块，但每个斑块中激活的峰值位置略有不同。根据这种观点，类别选择性的组织尺度会比示例选择性的组织尺度大。但是，人类受试者实验中尚无此类建议的经验证据。在这里，我们使用两种方法在两个数据集上比较类别和示例选择性的相对组织尺度：（i）通过研究 fMRI 数据的空间平滑对多体素选择性模式可靠性的有益影响；（ii）通过比较这些选择性模式的空间频率谱中较低和较高空间频率的相对权重。这些发现与以下假设一致，即构成物体之间更细微区别的刺激属性的选择性组织尺度比区分类别刺激属性的选择性组织尺度更精细。这一发现证实了腹侧视觉通路中存在多种组织尺度。
