Anesthesia

Abstract

This chapter describes current knowledge about functional brain modifications observed during anesthesia-induced alterations of consciousness and places it into the context of consciousness physiology and anesthesia mechanisms. Anesthesia is a unique research tool for studying consciousness, insofar as it allows differentially and reversibly altering several of its constituents. Recent evidence suggests that anesthesia produces unconsciousness through a breakdown of connectivity into brain networks that are known to play a role in the emergence of mental content. These findings are in line with, and corroborate to some extent, current theories of conscious perception. Although anesthetic agents have effects on neural pathways controlling sleep and arousal, accumulating elements suggest that unconsciousness during general anesthesia occurs through mechanisms that are different from those of physiological sleep. Additional scientific exploration is still needed to understand the link between known biochemical targets of anesthetic agents, their effect on sleep-arousal systems, and the observed effects on consciousness networks. There is also a need for -precising the exact sequence of events during transitions across consciousness states, for each type of anesthetic agents.