• Vincent Bonhomme, Pierre Boveroux, Pol Hans, Jean François Brichant, Audrey Vanhaudenhuyse, Melanie Boly, and Steven Laureys.
• University Department of Anesthesia and ICM, CHR Citadelle, Belgium. vincent.bonhomme@chu.ulg.ac.be
• Curr Opin Anaesthesiol. 2011 Oct 1;24(5):474-9.

Purpose Of ReviewTo describe recent studies exploring brain function under the influence of hypnotic anesthetic agents, and their implications on the understanding of consciousness physiology and anesthesia-induced alteration of consciousness.Recent FindingsCerebral cortex is the primary target of the hypnotic effect of anesthetic agents, and higher-order association areas are more sensitive to this effect than lower-order processing regions. Increasing concentration of anesthetic agents progressively attenuates connectivity in the consciousness networks, while connectivity in lower-order sensory and motor networks is preserved. Alteration of thalamic sub-cortical regulation could compromise the cortical integration of information despite preserved thalamic activation by external stimuli. At concentrations producing unresponsiveness, the activity of consciousness networks becomes anticorrelated with thalamic activity, while connectivity in lower-order sensory networks persists, although with cross-modal interaction alterations.SummaryAccumulating evidence suggests that hypnotic anesthetic agents disrupt large-scale cerebral connectivity. This would result in an inability of the brain to generate and integrate information, while external sensory information is still processed at a lower order of complexity.

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