Orientation selectivity of motion-boundary responses in human visual cortex.
Orientation selectivity of motion-boundary responses in human visual cortex.
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DOI：
10.1152/jn.00400.2010
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发表时间：
2010-09
影响因子：
2.5
通讯作者：
J. Larsson;D. Heeger;M. Landy
中科院分区：
文献类型：
--
作者：
J. Larsson;D. Heeger;M. Landy
当对象相对于观察者移动时，运动边界(视觉运动方向的局部变化)自然出现。在人类视觉皮质中，神经成像研究已经确定了一个区域(动态枕区[KO])，它对运动边界刺激的反应比对透明运动刺激的反应更强烈。然而，一些功能磁共振成像(FMRI)研究表明，KO可能包括多个视区，猕猴视皮层的单单位研究发现，V2、V3和V4区对运动边界方向具有选择性，这意味着运动边界选择性可能不限于单个区域。目前尚不清楚fMRI对运动边界的反应是否像预期的那样对运动边界方向具有选择性，如果这些反应反映了运动边界选择神经元的群体活动。我们使用了一种事件相关的fMRI适应方案来测量人类视觉皮质对运动边界的方位选择性反应。在每个试验中，我们测量了在适配器刺激(垂直或水平运动边界栅格)之后出现的探头刺激的反应。探头刺激是与适配器刺激平行或垂直的运动边界光栅，或者是透明运动刺激。在多个纹状体外视觉区域观察到对运动边界的方位选择性适应--在测试和适配器刺激相互平行的试验中，反应较小。与非适应反应相比，V3A、V3B、LO1、LO2和V7适应能力最强。在我们的数据中，大多数表现出方位选择性适应的视觉区域也表现出对运动边界的反应偏好，而不是透明运动，这表明先前被证明对运动边界做出反应的大多数人类视觉区域也对运动边界方向具有选择性。这些结果表明，选择运动边界定向的神经元分布在多个人类视觉皮质区域，并反对存在专门处理运动边界的单一区域或区域。
Motion boundaries (local changes in visual motion direction) arise naturally when objects move relative to an observer. In human visual cortex, neuroimaging studies have identified a region (the kinetic occipital area [KO]) that responds more strongly to motion-boundary stimuli than to transparent-motion stimuli. However, some functional magnetic resonance imaging (fMRI) studies suggest that KO may encompass multiple visual areas and single-unit studies in macaque visual cortex have identified neurons selective for motion-boundary orientation in areas V2, V3, and V4, implying that motion-boundary selectivity may not be restricted to a single area. It is not known whether fMRI responses to motion boundaries are selective for motion-boundary orientation, as would be expected if these responses reflected the population activity of motion-boundary-selective neurons. We used an event-related fMRI adaptation protocol to measure orientation-selective responses to motion boundaries in human visual cortex. On each trial, we measured the response to a probe stimulus presented after an adapter stimulus (a vertical or horizontal motion-boundary grating). The probe stimulus was either a motion-boundary grating oriented parallel or orthogonal to the adapter stimulus or a transparent-motion stimulus. Orientation-selective adaptation for motion boundaries--smaller responses for trials in which test and adapter stimuli were parallel to each other--was observed in multiple extrastriate visual areas. The strongest adaptation, relative to the unadapted responses, was found in V3A, V3B, LO1, LO2, and V7. Most of the visual areas that exhibited orientation-selective adaptation in our data also showed response preference for motion boundaries over transparent motion, indicating that most of the human visual areas previously shown to respond to motion boundaries are also selective for motion-boundary orientation. These results suggest that neurons selective for motion-boundary orientation are distributed across multiple human visual cortical areas and argue against the existence of a single region or area specialized for motion-boundary processing.