Harris Alison, Aguirre Geoffrey Karl
Department of Neurology, University of Pennsylvania, Philadelphia, PA 19104, USA.
J Cogn Neurosci. 2008 May;20(5):863-78. doi: 10.1162/jocn.2008.20509.
Although face perception is often characterized as depending on holistic, rather than part-based, processing, there is behavioral evidence for independent representations of face parts. Recent work has linked "face-selective" regions defined with functional magnetic resonance imaging (fMRI) to holistic processing, but the response of these areas to face parts remains unclear. Here we examine part-based versus holistic processing in "face-selective" visual areas using face stimuli manipulated in binocular disparity to appear either behind or in front of a set of stripes [Nakayama, K., Shimojo, S., & Silverman, G. H. Stereoscopic depth: Its relation to image segmentation, grouping, and the recognition of occluded objects. Perception, 18, 55-68, 1989]. While the first case will be "filled in" by the visual system and perceived holistically, we demonstrate behaviorally that the latter cannot be completed amodally, and thus is perceived as parts. Using these stimuli in fMRI, we found significant responses to both depth manipulations in inferior occipital gyrus and middle fusiform gyrus (MFG) "face-selective" regions, suggesting that neural populations in these areas encode both parts and wholes. In comparison, applying these depth manipulations to control stimuli (alphanumeric characters) elicited much smaller signal changes within face-selective regions, indicating that the part-based representation for faces is separate from that for objects. The combined adaptation data also showed an interaction of depth and familiarity within the right MFG, with greater adaptation in the back (holistic) condition relative to parts for familiar but not unfamiliar faces. Together, these data indicate that face-selective regions of occipito-temporal cortex engage in both part-based and holistic processing. The relative recruitment of such representations may be additionally influenced by external factors such as familiarity.
尽管面部感知通常被认为依赖于整体加工而非基于部分的加工，但有行为学证据表明面部各部分存在独立表征。最近的研究将通过功能磁共振成像（fMRI）定义的“面部选择性”区域与整体加工联系起来，但这些区域对面部各部分的反应仍不清楚。在这里，我们使用双眼视差操纵的面部刺激来检查枕颞叶“面部选择性”视觉区域中基于部分的加工与整体加工，使这些面部刺激看起来要么在一组条纹后面，要么在条纹前面[中山健、下条信辅、西尔弗曼，G.H.立体深度：它与图像分割、分组以及遮挡物体识别的关系。《感知》，18，55 - 68，1989年]。虽然第一种情况会被视觉系统“填充”并被整体感知，但我们通过行为学证明，后一种情况无法以无模态方式完成，因此被感知为部分。在fMRI中使用这些刺激，我们发现枕下回和梭状回中部（MFG）“面部选择性”区域对两种深度操纵都有显著反应，这表明这些区域的神经群体对面部各部分和整体都进行编码。相比之下，将这些深度操纵应用于对照刺激（字母数字字符）时，在面部选择性区域内引起的信号变化要小得多，这表明面部基于部分的表征与物体的不同。综合适应数据还显示，右侧MFG内深度和熟悉度之间存在相互作用，对于熟悉的面孔，相对于部分而言，在背面（整体）条件下有更大的适应性，但不熟悉的面孔则不然。总之，这些数据表明枕颞叶皮质的面部选择性区域既参与基于部分的加工，也参与整体加工。这种表征的相对激活可能还会受到熟悉度等外部因素的额外影响。
