Toward a Unified Theory of Narcosis: Brain Imaging Evidence for a Thalamocortical Switch as the Neurophysiologic Basis of Anesthetic-Induced Unconsciousness

Authors: Alkire M.T.¹; Haier R.J.²; Fallon J.H.³

Source: Consciousness and Cognition, Volume 9, Number 3, September 2000 , pp. 370-386(17)

Publisher: Academic Press

Abstract:

A unifying theory of general anesthetic-induced unconsciousness must explain the common mechanism through which various anesthetic agents produce unconsciousness. Functional-brain-imaging data obtained from 11 volunteers during general anesthesia showed specific suppression of regional thalamic and midbrain reticular formation activity across two different commonly used volatile agents. These findings are discussed in relation to findings from sleep neurophysiology and the implications of this work for consciousness research. It is hypothesized that the essential common neurophysiologic mechanism underlying anesthetic-induced unconsciousness is, as with sleep-induced unconsciousness, a hyperpolarization block of thalamocortical neurons. A model of anesthetic-induced unconsciousness is introduced to explain how the plethora of effects anesthetics have on cellular functioning ultimately all converge on a single neuroanatomic/neurophysiologic system, thus providing for a unitary physiologic theory of narcosis related to consciousness. Copyright 2000 Academic Press.

Keywords: Key Words: anesthesia; brain imaging; consciousness; corticothalamic; halothane; hyperpolarization; isoflurane; mechanism; thalamocortical; positron emission tomography; sleep

Language: English

Document Type: Research article

Affiliations: 1: Department of Anesthesiology, University of California at Irvine, Irvine, California, 92697 2: Department of Pediatrics, University of California at Irvine, Irvine, California, 92697 3: Department of Anatomy and Neurobiology, University of California at Irvine, Irvine, California, 92697

Publication date: 2000-09-01

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• In this Subject: Psychology
• By this author: Alkire M.T. ;  Haier R.J. ;  Fallon J.H.

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