Functional MRI in Anesthesia and Resting-State Networks

Abstract

This chapter reviews current knowledge of the effects of hypnotic anesthetic agents on brain resting-state networks (RSNs) that sustain consciousness. Although full exploration of the networks under anesthesia is not yet available, current evidence indicates that anesthetic agents with hypnotic properties dose-dependently modulate RSN functioning. Each anesthetic agent has specific effects that are not uniform within a given network and probably correlate with the specific clinical features observed when one agent or another is used. Observations made on RSNs during anesthesia are supplementary arguments to link the networks with specific aspects of consciousness and connectedness to the environment and to confirm their physiological functions. The precise link between observations made on RSNs during anesthesia and known biochemical targets of anesthetic agents, or their effects on systems that regulate the sleep–wake cycle, is not established yet. PET studies using radiolabeled probes that specifically target a neurotransmission system offer insights into the links. New technological advances and modes of functional data analysis, such as Granger causality and dynamic causal modeling, will help in obtaining a more in-depth exploration of the complex interactions between brain regions, their modulation by anesthesia, and their role in information processing by the brain. Effects of hypnosis on RSNs also have been studied. The hypnotic state is useful for performing surgical procedures and explorations without general anesthesia. The hypnotic state is associated with specific changes in the activity of RSNs that confirm hypnosis as a specific brain state, different from normal wakeful consciousness and anesthetic states.