Highly connected and highly variable: A Core brain network during resting state supports Propofol-induced unconsciousness.

Brain regions that are both highly connected to other hub regions (rich-club) and variable in their module membership across time are candidates for the neural correlates of consciousness. In resting-state fMRI data from 21 subjects, such regions were located in prefrontal and temporoparietal cortices. Dynamic analysis revealed two recurring brain states: one dominated by these candidate regions and the other by primary sensory/motor regions. The candidate-dominated state was temporally more stable, suggesting it sustains conscious content. The functional connectedness and modular variability of these candidates decreased with propofol-induced loss of consciousness.

Study at a glance

Abstract

Despite that leading theories of consciousness make diverging predictions for where and how neural activity gives rise to subjective experience, they all seem to partially agree that the neural correlates of consciousness (NCC) require globally integrated brain activity across a network of functionally specialized modules. However, it is not clear yet whether such functional configurations would be able to identify the NCC. We scanned resting-state fMRI data from 21 subjects during wakefulness, propofol-induced sedation, and anesthesia. Graph-theoretical analyses were conducted on awake fMRI data to search for the NCC candidates as brain regions that exhibit both high rich-clubness and high modular variability, which were found to locate in prefrontal and temporoparietal cortices. Another independent data set of 10 highly-sampled subjects was used to validate the NCC distribution at the individual level. Brain module-based dynamic analysis revealed two discrete reoccurring brain states, one of which was dominated by the NCC candidates (state 1), while the other state was predominately composed of primary sensory/motor regions (state 2). Moreover, state 1 appeared to be temporally more stable than state 2, suggesting that the identified NCC members could sustain conscious content as metastable network representations. Finally, we showed that the identified NCC was modulated in terms of functional connectedness and modular variability in response to the loss of consciousness induced by propofol anesthesia. This work offers a framework to search for neural correlates of consciousness by charting the brain network topology and provides new insights into understanding the roles of different regions in underpinning human consciousness.