Propofol when administrated for general anesthesia induces oscillatory dynamic brain states which are thought to underlie the drugs pharmacological effects. Despite the elucidation regarding the mechanisms of action at the molecular level, the manner how propofol acts on neural circuits leading to unconsciousness is still unclear. To identify possible mechanisms, the spatial-temporal patterns of functional connectivity established among cortical areas need to be described. The present research was based on the analysis of sub-dural ECoG records from macaques under anesthetic induction experiments. Granger causality in the frequency domain was used to infer functional interactions in five physiological frequency bands serially at every five seconds throughout the experiment. These time-resolved functional networks permitted to observe the unfolding of the anesthetic induction and compare networks respective to distinct conditions. Within about one minute after propofol administration, functional connectivity started to gradually increase for about 4-5 minutes, then began to decrease until the LOC was achieved. During the transition, it was also evidenced a predominant Granger causality flow parting from occipital and temporal areas to frontal and parietal regions. During general anesthesia the local connectivity of the occipital lobe raised, and also did the interactions, established among the occipital and temporal lobes. Functional interactions parting from frontal and parietal lobes to temporal and occipital areas had been mainly compromised. The research brings a detailed description of the propofol effects on large-scale cortical functional connectivity along with the anesthetic induction in non-human primates, and it is one of the first studies to describe the dynamics of functional connectivity during the transitional state that precedes LOC.
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