Altered hub configurations during propofol-induced loss of consciousness

Graph-theoretical analysis of human brain functional networks based on functional magnetic resonance imaging (fMRI) have supported the existence of highly connected hub regions that may play a key role in brain function and cognition. Here, we investigated the hub distributions of 16 healthy volunteers during wakefulness and propofol-induced loss of consciousness (both light sedation and deep sedation). Functional connectivity between 160 cortical and subcortical regions was measured by correlation analysis and then thresholded to construct undirected graphs. We found that during wakefulness state highly connected hubs included bilateral angular, precuneus, posterior cingulate (PCC), superior frontal gyrus (SFG), ventrolateral frontal cortex (vFC), supplementary motor area (SMA) and pre-SMA, most of the which were in the default-mode network (DMN). However, during light sedation, we observed that hubs were mainly in posterior part of the brain (inferior parietal lobule, inferior temporal, occipital). And the major hubs during deep sedation were in the occipital lobe and cerebellum. Compared with wakefulness, the hub structures were significantly changed from heteromodal association cortex to unimodal association and primary cortices. Our findings support a reduction in integrated information and a topological reconfiguration during decreasing levels of consciousness.