Characterization of neural communication dynamics in the Ventral Attention Network across distinct spatial and spatio-temporal scales

Abstract

The Ventral Attention Network (VAN) is involved in reorienting attention from an ongoing task when a salient (pop-out) stimulus is detected in the environment. Previous neuroimaging studies have extensively evaluated the structural and functional connectivity of the VAN. However, directed effective connectivity within the network and the neural oscillations driving it still remain elusive. Functional magnetic resonance imaging (fMRI) studies have not been able to address this issue due to lack of appropriate temporal resolution required to capture the process of reorientation. In this study, we recorded scalp electroencephalography (EEG) and behavioural data from healthy human volunteers, obtained saliency-specific spectral changes, localized the sources underlying the spectral power modulations with individual-specific structural MRI scans, reconstructed the waveforms of the sources and investigated the causal relationships between the areas of the VAN using Granger causality (GC). Using a custom-designed experiment involving visual search on static images and a dynamic motion tracking task, we investigated the neural processing of salient distractors operating at very slow and very fast time scales, respectively. Our results revealed how a task-independent but context-specific VAN encompassing the right insula, the right lateral pre-frontal cortex, the anterior and the posterior right temporo-parietal junction communicating in the alpha frequency band (8-12 Hz) supports saliency processing.