Reppas J B, Niyogi S, Dale A M, Sereno M I, Tootell R B
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Nature. 1997 Jul 10;388(6638):175-9. doi: 10.1038/40633.
Edges are important in the interpretation of the retinal image. Although luminance edges have been studied extensively, much less is known about how or where the primate visual system detects boundaries defined by differences in surface properties such as texture, motion or binocular disparity. Here we use functional magnetic resonance imaging (fMRI) to localize human visual cortical activity related to the processing of one such higher-order edge type: motion boundaries. We describe a robust fMRI signal that is selective for motion segmentation. This boundary-specific signal is present, and retinotopically organized, within early visual areas, beginning in the primary visual cortex (area V1). Surprisingly, it is largely absent from the motion-selective area MT/V5 and far extrastriate visual areas. Changes in the surface velocity defining the motion boundaries affect the strength of the fMRI signal. In parallel psychophysical experiments, the perceptual salience of the boundaries shows a similar dependence on surface velocity. These results demonstrate that information for segmenting scenes by relative motion is represented as early as V1.
边缘在视网膜图像的解读中很重要。尽管亮度边缘已得到广泛研究，但对于灵长类视觉系统如何以及在何处检测由表面属性差异（如纹理、运动或双眼视差）所定义的边界，我们所知甚少。在此，我们使用功能磁共振成像（fMRI）来定位与一种此类高阶边缘类型——运动边界的处理相关的人类视觉皮层活动。我们描述了一种对运动分割具有选择性的强大fMRI信号。这种边界特异性信号在早期视觉区域中存在且呈视网膜拓扑组织，始于初级视觉皮层（V1区）。令人惊讶的是，在运动选择性区域MT/V5和远外侧视觉区域中该信号基本不存在。定义运动边界的表面速度变化会影响fMRI信号的强度。在并行的心理物理学实验中，边界的感知显著性对表面速度表现出类似的依赖性。这些结果表明，通过相对运动分割场景的信息早在V1区就有表征。
