Cognitive Brain Dynamics Lab, National Brain Research Centre, Manesar, NH-8, Gurgaon, Haryana 122052, India.
Cognitive Brain Dynamics Lab, National Brain Research Centre, Manesar, NH-8, Gurgaon, Haryana 122052, India.
Neuroimage. 2021 May 1;231:117869. doi: 10.1016/j.neuroimage.2021.117869. Epub 2021 Feb 17.
Previous neuroimaging studies have extensively evaluated the structural and functional connectivity of the Ventral Attention Network (VAN) and its role in reorienting attention in the presence of a salient (pop-out) stimulus. However, a detailed understanding of the "directed" functional connectivity within the VAN during the process of reorientation remains elusive. Functional magnetic resonance imaging (fMRI) studies have not adequately addressed this issue due to a lack of appropriate temporal resolution required to capture this dynamic process. The present study investigates the neural changes associated with processing salient distractors operating at a slow and a fast time scale using custom-designed experiment involving visual search on static images and dynamic motion tracking, respectively. We recorded high-density scalp electroencephalography (EEG) from healthy human volunteers, obtained saliency-specific behavioral and spectral changes during the tasks, localized the sources underlying the spectral power modulations with individual-specific structural MRI scans, reconstructed the waveforms of the sources and finally, investigated the causal relationships between the sources using spectral Granger-Geweke Causality (GGC). We found that salient stimuli processing, across tasks with varying spatio-temporal complexities, involves a characteristic modulation in the alpha frequency band which is executed primarily by the nodes of the VAN constituting the temporo-parietal junction (TPJ), the insula and the lateral prefrontal cortex (lPFC). The directed functional connectivity results further revealed the presence of bidirectional interactions among prominent nodes of right-lateralized VAN, corresponding only to the trials with saliency. Thus, our study elucidates the invariant network mechanisms for processing saliency in visual attention tasks across diverse time-scales.
先前的神经影像学研究广泛评估了腹侧注意网络 (VAN) 的结构和功能连接及其在存在突出（弹出）刺激时重新定向注意力的作用。然而，对于重新定向过程中 VAN 内的“定向”功能连接的详细理解仍然难以捉摸。由于缺乏捕获此动态过程所需的适当时间分辨率，功能磁共振成像 (fMRI) 研究尚未充分解决此问题。本研究使用分别涉及静态图像视觉搜索和动态运动跟踪的定制实验，研究了与处理在慢和快时间尺度上运行的突出干扰物相关的神经变化。我们从健康的人类志愿者记录了高密度头皮脑电图 (EEG)，在任务期间获得了与显着性相关的行为和频谱变化，使用个体特定的结构 MRI 扫描定位了频谱功率调制的源，重建了源的波形，并最后使用频谱格兰杰-格威克因果关系 (GGC) 研究了源之间的因果关系。我们发现，跨具有不同时空复杂度的任务处理突出刺激，涉及特征性的 alpha 频带调制，主要由构成颞顶联合 (TPJ)、岛叶和外侧前额叶皮层 (lPFC) 的 VAN 节点执行。定向功能连接结果进一步揭示了仅对应于显着性试验的右偏 VAN 突出节点之间存在双向相互作用。因此，我们的研究阐明了视觉注意任务中处理显着性的不变网络机制，跨越不同的时间尺度。
