Visual search has been commonly used to study the neural correlates of attentional allocation in space. Recent electrophysiological research has disentangled distractor processing from target processing, showing that these mechanisms appear to operate in parallel and show electric fields of opposite polarity. Nevertheless, the localization and exact nature of this activity is unknown. Here, using MEG in humans, we provide a spatiotemporal characterization of target and distractor processing in visual cortex. We demonstrate that source activity underlying target- and distractor-processing propagates in parallel as fast and slow sweep from higher to lower hierarchical levels in visual cortex. Importantly, the fast propagating target-related source activity bypasses intermediate levels to go directly to V1, and this V1 activity correlates with behavioral performance. These findings suggest that reentrant processing is important for both selection and attenuation of stimuli, and such processing operates in parallel feedback loops.

视觉搜索已普遍用于研究空间中注意力分配的神经相关性。最近的电生理研究已将干扰物处理与目标处理分离开来，表明这些机制似乎并行运行，并显示相反极性的电场。但是，该活动的定位和确切性质尚不清楚。在这里，在人类中使用MEG，我们提供了视觉皮层中目标和干扰物处理的时空特征。我们证明了在目标皮层和干扰物处理基础上的源活动在视皮层中从较高到较低层次的快速和缓慢扫描中并行传播。重要的是，与目标有关的快速传播源活动会绕过中间级别直接进入V1，并且此V1活动与行为表现相关。这些发现表明，折返处理对于刺激的选择和衰减都很重要，并且这种处理在并行反馈回路中进行。