Freeman Jeremy, Donner Tobias H, Heeger David J
Center for Neural Science, New York University, New York, NY 10003, USA.
J Vis. 2011 Apr 26;11(4):15. doi: 10.1167/11.4.15.
During object perception, the brain integrates simple features into representations of complex objects. A perceptual phenomenon known as visual crowding selectively interferes with this process. Here, we use crowding to characterize a neural correlate of feature integration. Cortical activity was measured with functional magnetic resonance imaging, simultaneously in multiple areas of the ventral visual pathway (V1-V4 and the visual word form area, VWFA, which responds preferentially to familiar letters), while human subjects viewed crowded and uncrowded letters. Temporal correlations between cortical areas were lower for crowded letters than for uncrowded letters, especially between V1 and VWFA. These differences in correlation were retinotopically specific, and persisted when attention was diverted from the letters. But correlation differences were not evident when we substituted the letters with grating patches that were not crowded under our stimulus conditions. We conclude that inter-area correlations reflect feature integration and are disrupted by crowding. We propose that crowding may perturb the transformations between neural representations along the ventral pathway that underlie the integration of features into objects.
在物体感知过程中，大脑将简单特征整合为复杂物体的表征。一种被称为视觉拥挤的感知现象会选择性地干扰这一过程。在此，我们利用拥挤现象来表征特征整合的神经关联。在人类受试者观看拥挤和不拥挤字母时，通过功能磁共振成像同时测量腹侧视觉通路多个区域（V1 - V4以及对熟悉字母有优先反应的视觉词形区VWFA）的皮质活动。对于拥挤字母，皮质区域之间的时间相关性低于不拥挤字母，尤其是在V1和VWFA之间。这些相关性差异在视网膜拓扑学上具有特异性，并且当注意力从字母上转移时依然存在。但是，当我们用在我们的刺激条件下不会产生拥挤的光栅斑块替换字母时，相关性差异并不明显。我们得出结论，区域间相关性反映了特征整合，并且会被拥挤所破坏。我们提出，拥挤可能会扰乱腹侧通路中神经表征之间的转换，而这种转换是将特征整合为物体的基础。
