Toward a Unified Theory of Narcosis: Brain Imaging Evidence for a Thalamocortical Switch as the Neurophysiologic Basis of Anesthetic-Induced Unconsciousness
David Bourget (Western Ontario)
David Chalmers (ANU, NYU)
Rafael De Clercq
Jack Alan Reynolds
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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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Lawrence M. Ward (2011). The Thalamic Dynamic Core Theory of Conscious Experience. Consciousness and Cognition 20 (2):464-486.
UnCheol Lee, George A. Mashour, Seunghwan Kim, Gyu-Jeong Noh & Byung-Moon Choi (2009). Propofol Induction Reduces the Capacity for Neural Information Integration: Implications for the Mechanism of Consciousness and General Anesthesia. Consciousness and Cognition 18 (1):56-64.
Shi-Jiang Li Jingsheng Zhou, Xiaolin Liu, Weiqun Song, Yanhui Yang, Zhilian Zhao, Feng Ling, Anthony G. Hudetz (2011). Specific and Nonspecific Thalamocortical Functional Connectivity in Normal and Vegetative States. Consciousness and Cognition 20 (2):257.
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