Massachusetts Institute of Technology, 46-4141, Cambridge, Massachusetts 02139, USA.
Hum Brain Mapp. 2010 Sep;31(9):1395-407. doi: 10.1002/hbm.20946.
Visual filling-in occurs when a retinally stabilized object undergoes perceptual fading. As the term "filling-in" implies, it is commonly believed that information about the apparently vanished object is lost and replaced solely by information arising from the surrounding background. Here we report multivoxel pattern analysis fMRI data that challenge this long-held belief. When subjects view blue disks on a red background while fixating, the stimulus and background appear to turn a uniform purple upon perceptual fading, suggesting that a feature mixing mechanism may underlie color filling-in. We find that ensemble fMRI signals in retinotopic visual areas reliably predict (i) which of three colors a subject reports seeing; (ii) whether a subject is in a perceptually filled-in state or not; and (iii) furthermore, while subjects are in the perceptual state of filling-in, the BOLD signal activation pattern in the sub-areas of V1 corresponding to the location of the blue disks behaves as if subjects are in fact viewing a perceptually mixed color (purple), rather than the color of the disks (blue) or the color of the background (red). These results imply that the mechanism of filling-in in stimuli in which figure and background surfaces are equated is a process of "feature mixing", not "feature replacement". These data indicate that feature mixing may involve cortical areas as early as V1.
当一个视网膜稳定的物体经历感知消失时，就会出现视觉填充。正如“填充”一词所暗示的，人们普遍认为，关于明显消失的物体的信息丢失了，而仅仅被来自周围背景的信息所取代。在这里，我们报告了多体素模式分析 fMRI 数据，这些数据挑战了这一长期存在的观点。当被试在注视时观察红色背景上的蓝色圆盘时，刺激和背景在感知消失后似乎会变成均匀的紫色，这表明可能存在一种特征混合机制来解释颜色填充。我们发现，在视区视觉区域的整体 fMRI 信号可以可靠地预测：(i) 被试报告看到的三种颜色中的哪一种；(ii) 被试是否处于感知填充状态；(iii) 更进一步地，当被试处于填充的感知状态时，V1 中对应蓝色圆盘位置的子区域的 BOLD 信号激活模式表现得好像被试实际上正在观看感知混合的颜色（紫色），而不是圆盘的颜色（蓝色）或背景的颜色（红色）。这些结果表明，在图形和背景表面相等的刺激中，填充的机制是一个“特征混合”的过程，而不是“特征替换”。这些数据表明，特征混合可能早在 V1 就涉及到了皮层区域。
