| Summary: | The question of how structurally and pharmacologically diverse general anesthetics disrupt consciousness has persisted since the 19th century. There has traditionally been a significant focus on bottom-up mechanisms of anesthetic action, in terms of sensory processing, arousal systems and structural scales. However, recent evidence suggests that the neural mechanisms of anesthetic-induced unconsciousness may involve a top-down process, which parallels current perspectives on the neurobiology of conscious experience itself. This article considers various arguments for top-down mechanisms of anesthetic-induced unconsciousness, with a focus on sensory processing and sleep-wake networks. Furthermore, recent theoretical work is discussed to highlight the possibility that top-down explanations may be causally sufficient, even assuming critical bottom-up events.
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