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A Neural Basis of the Anesthetic State. J. D. French, M. Verzeano, and H. W. Magoun. Pp. 519-529.
These studies continue a series of papers from the University of California School of Medicine at Los Angeles which relate to the central reticular activating system in the brain stem and its effects on states of sleep and arousal. In the first of these two papers, French, Verzeano, and Magoun, working on monkeys, describe and delineate a medial extralemniscal sensory system in the brain stem which conducts afferent stimuli to the cortex in pathways distinct from the well-known classical sensory routes. While both systems conduct afferent impulses simultaneously to the cortex, the classical lateral pathways subserve perception and discriminatory functions while the medical system serves to arouse consciousness or alertness without which the above-mentioned sensory discrimination, and effective responses to it, would be impossible. Information delivered over the lateral system is essential for the perception and recognition of stimuli and for their localization. The medical system maintains the state of consciousness and may be involved in management of gradations of attention superimposed upon inattentive wakefulness.
In the second paper, the authors study the effects of ether and pentobarbital sodium on conduction in this central system in order to help in understanding the anesthetized state. In these experiments, performed on ten macacus mulattus monkeys, potentials were compared in both medial and lateral conduction routes under various states of wakefulness and sleep induced by anesthesia. The medial system was seen to be affected earlier than was the lateral system by the administration of ether or pentobarbital sodium. The evidence suggests that the central brain stem system is more susceptible to anesthetic blockade than the lateral pathways, and that depression of activity in these areas participates to a considerable degree in production of the anesthet