Key Laboratory of Brain, Cognition, and Education Sciences, Ministry of Education, South China Normal University, 510631 Guangzhou, Guangdong, China.
School of Psychology, South China Normal University, 510631 Guangzhou, Guangdong, China.
Proc Natl Acad Sci U S A. 2020 Dec 1;117(48):30836-30847. doi: 10.1073/pnas.1922832117. Epub 2020 Nov 16.
Figure-ground modulation, i.e., the enhancement of neuronal responses evoked by the figure relative to the background, has three complementary components: edge modulation (boundary detection), center modulation (region filling), and background modulation (background suppression). However, the neuronal mechanisms mediating these three modulations and how they depend on awareness remain unclear. For each modulation, we compared both the cueing effect produced in a Posner paradigm and fMRI blood oxygen-level dependent (BOLD) signal in primary visual cortex (V1) evoked by visible relative to invisible orientation-defined figures. We found that edge modulation was independent of awareness, whereas both center and background modulations were strongly modulated by awareness, with greater modulations in the visible than the invisible condition. Effective-connectivity analysis further showed that the awareness-dependent region-filling and background-suppression processes in V1 were not derived through intracortical interactions within V1, but rather by feedback from the frontal eye field (FEF) and dorsolateral prefrontal cortex (DLPFC), respectively. These results indicate a source for an awareness-dependent figure-ground segregation in human prefrontal cortex.
图形-背景调制，即相对于背景增强图形诱发的神经元反应，具有三个互补的成分：边缘调制（边界检测）、中心调制（区域填充）和背景调制（背景抑制）。然而，介导这三种调制的神经元机制以及它们如何依赖于意识尚不清楚。对于每种调制，我们比较了在 Posner 范式中产生的提示效应和 fMRI 血氧水平依赖（BOLD）信号在初级视觉皮层（V1）中由可见的相对于不可见的定向定义图形引起的效应。我们发现边缘调制与意识无关，而中心和背景调制都受到意识的强烈调制，在可见条件下调制幅度更大。有效连接分析进一步表明，V1 中的意识依赖的区域填充和背景抑制过程不是通过 V1 内的皮质内相互作用产生的，而是分别来自额叶眼区（FEF）和背外侧前额叶皮层（DLPFC）的反馈。这些结果表明，在人类前额叶皮层中存在一种意识依赖的图形-背景分离的来源。
