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

Consciousness and Cognition 9 (3):370-386 (2000)
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
Keywords *Consciousness States  *General Anesthetics  *Neurons  *Reticular Formation  *Thalamus  Neuroanatomy  Neurophysiology
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DOI 10.1006/ccog.1999.0423
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E. Roy John (2001). A Field Theory of Consciousness. Consciousness and Cognition 10 (2):184-213.

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Pamela Flood (2002). General Anesthetics. In Elaine Perry, Heather Ashton & Allan Young (eds.), Neurochemistry of Consciousness: Neurotransmitters in Mind. John Benjamins 149-162.

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