The role of inferior frontal junction in controlling the spatially global effect of feature-based attention in human visual areas

Feature-based attention has a spatially global effect, i.e., responses to stimuli that share features with an attended stimulus are enhanced not only at the attended location but throughout the visual field. However, how feature-based attention modulates cortical neural responses at unattended locations remains unclear. Here we used functional magnetic resonance imaging (fMRI) to examine this issue as human participants performed motion- (Experiment 1) and color- (Experiment 2) based attention tasks. Results indicated that, in both experiments, the respective visual processing areas (middle temporal area [MT+] for motion and V4 for color) as well as early visual, parietal, and prefrontal areas all showed the classic feature-based attention effect, with neural responses to the unattended stimulus significantly elevated when it shared the same feature with the attended stimulus. Effective connectivity analysis using dynamic causal modeling (DCM) showed that this spatially global effect in the respective visual processing areas (MT+ for motion and V4 for color), intraparietal sulcus (IPS), frontal eye field (FEF), medial frontal gyrus (mFG), and primary visual cortex (V1) was derived by feedback from the inferior frontal junction (IFJ). Complementary effective connectivity analysis using Granger causality modeling (GCM) confirmed that, in both experiments, the node with the highest outflow and netflow degree was IFJ, which was thus considered to be the source of the network. These results indicate a source for the spatially global effect of feature-based attention in the human prefrontal cortex.基于特征的注意具有空间全域效应，即当刺激与被注意刺激共享特征时，不仅在被注意位置，而是在整个视野内，对该刺激的神经响应都会得到增强。然而，基于特征的注意如何调控非注意位置的皮层神经响应，目前仍不明确。本研究采用功能磁共振成像（functional magnetic resonance imaging, fMRI），在人类被试完成运动定向注意任务（实验1）与颜色定向注意任务（实验2）时，对这一科学问题展开探究。结果显示，在两项实验中，相应的视觉加工脑区——运动加工相关的颞中区（middle temporal area, MT+）与颜色加工相关的V4区——以及早期视觉皮层、顶叶与前额叶皮层，均表现出经典的基于特征的注意效应：当非注意刺激与被注意刺激共享相同特征时，其神经响应会显著升高。采用动态因果建模（dynamic causal modeling, DCM）开展的有效连接分析表明，上述视觉加工脑区、顶内沟（intraparietal sulcus, IPS）、额眼区（frontal eye field, FEF）、内侧额回（medial frontal gyrus, mFG）以及初级视觉皮层（primary visual cortex, V1）中出现的空间全域效应，源自额下回联合区（inferior frontal junction, IFJ）的反馈投射。采用格兰杰因果建模（Granger causality modeling, GCM）进行的补充性有效连接分析证实，在两项实验中，流出连接与净连接程度最高的脑区均为IFJ，因此该脑区被认定为该神经调控网络的源头。上述结果表明，基于特征的注意的空间全域效应，其神经源头位于人类前额叶皮层。