Lerner Y, Hendler T, Ben-Bashat D, Harel M, Malach R
Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel.
Cereb Cortex. 2001 Apr;11(4):287-97. doi: 10.1093/cercor/11.4.287.
How are objects represented in the human visual cortex? Two conflicting theories suggest either a holistic representation, in which objects are represented by a collection of object templates, or a part-based representation, in which objects are represented as collections of features or object parts. We studied this question using a gradual object-scrambling paradigm in which pictures of objects (faces and cars) were broken in a stepwise manner into an increasing number of blocks. Our results reveal a hierarchical axis oriented anterior--posteriorly in the organization of ventral object-areas. Along this axis, representations are arranged in bands of increasing sensitivity to image scrambling. The axis starts in early visual areas through retinotopic areas V4/V8 and continues into the lateral-occipital sulcus dorsally and the posterior fusiform girus ventrally, corresponding together to the previously described object-related lateral occipital complex (LOC). Regions showing the highest sensitivity to scrambling tended to be located at the most anterior-lateral regions of the complex. In these more anterior regions, breaking the images into 16 parts produced a significant reduction in activation. Interestingly, activation was not affected when images were cut in two halves, either horizontally or vertically. Car images generally produced a weaker activation compared to faces in the lateral occipital complex but showed the same tendency of increased scrambling sensitivity along the anterior--posterior axis. These results suggest the existence of a hierarchical axis along ventral occipito-temporal object-areas, in which the neuronal properties shift from sensitivity to local object features to a more global and holistic representation.
物体在人类视觉皮层中是如何被表征的？两种相互矛盾的理论提出了不同观点：一种是整体表征理论，即物体由一组物体模板来表征；另一种是基于部分的表征理论，即物体被表征为特征或物体部分的集合。我们使用一种渐进的物体打乱范式来研究这个问题，在该范式中，物体（面孔和汽车）的图片被逐步分割成越来越多的块。我们的结果揭示了腹侧物体区域组织中一条从前向后定向的层级轴。沿着这条轴，表征以对图像打乱敏感度不断增加的条带形式排列。这条轴始于早期视觉区域，经过视网膜拓扑区域V4/V8，然后背侧延伸至枕外侧沟，腹侧延伸至梭状回后部，这些区域共同对应于先前描述的与物体相关的枕外侧复合体（LOC）。对打乱最敏感的区域往往位于该复合体最前外侧的区域。在这些更靠前的区域，将图像分割成16部分会导致激活显著降低。有趣的是，当图像水平或垂直切成两半时，激活不受影响。在枕外侧复合体中，汽车图像通常比面孔图像产生的激活更弱，但在前后轴上也表现出相同的打乱敏感度增加趋势。这些结果表明，在腹侧枕颞物体区域存在一条层级轴，其中神经元属性从对局部物体特征的敏感度转变为更全局和整体的表征。
