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dc.contributor.authorSteyn-Ross, Moira L.
dc.contributor.authorSteyn-Ross, D. Alistair
dc.contributor.authorSleigh, James W.
dc.contributor.authorWilcocks, Lara C.
dc.coverage.spatialUnited Statesen_NZ
dc.date.accessioned2008-11-20T20:48:49Z
dc.date.available2008-11-20T20:48:49Z
dc.date.issued2001
dc.identifier.citationSteyn-Ross, M. L., Steyn-Ross, D. A., Sleigh, J. W. & Wilcocks, L. C. (2001). Toward a theory of the general-anesthetic-induced phase transition of the cerebral cortex. I. A thermodynamics analogy. Physical Review E, 64(1), 011917.en_US
dc.identifier.urihttps://hdl.handle.net/10289/1425
dc.description.abstractIn a recent paper the authors developed a stochastic model for the response of the cerebral cortex to a general anesthetic agent. The model predicted that there would be an anesthetic-induced phase change at the point of transition into unconsciousness, manifested as a divergence in the electroencephalogram spectral power, and a change in spectral energy distribution from being relatively broadband in the conscious state to being strongly biased towards much lower frequencies in the unconscious state. Both predictions have been verified in recent clinical measurements. In the present paper we extend the model by calculating the equilibrium distribution function for the cortex, allowing us to establish a correspondence between the cortical phase transition and the more familiar thermodynamic phase transitions. This correspondence is achieved by first identifying a cortical free energy function, then by postulating that there exists an inverse relationship between an anesthetic effect and a quantity we define as cortical excitability, which plays a role analogous to temperature in thermodynamic phase transitions. We follow standard thermodynamic theory to compute a cortical entropy and a cortical “heat capacity,” and we investigate how these will vary with anesthetic concentration. The significant result is the prediction that the entropy will decrease discontinuously at the moment of induction into unconsciousness, concomitant with a release of “latent heat” which should manifest as a divergence in the analogous heat capacity. There is clear clinical evidence of heat capacity divergence in historical anesthetic-effect measurements performed in 1977 by Stullken et al. [Anesthesiology 46, 28 (1977)]. The discontinuous step change in cortical entropy suggests that the cortical phase transition is analogous to a first-order thermodynamic transition in which the comatose-quiescent state is strongly ordered, while the active cortical state is relatively disordered.en_US
dc.language.isoen
dc.publisherAmerican Physical Societyen_NZ
dc.relation.urihttp://prola.aps.org/abstract/PRE/v64/i1/e011917en_US
dc.subjectthermodynamicsen_US
dc.titleToward a theory of the general-anesthetic-induced phase transition of the cerebral cortex. I. A thermodynamics analogyen_US
dc.typeJournal Articleen_US
dc.identifier.doi10.1103/PhysRevE.64.011917en_US
dc.relation.isPartOfPhysical Review Een_NZ
pubs.begin-page1en_NZ
pubs.elements-id42131
pubs.end-page15en_NZ
pubs.issue1en_NZ
pubs.volume64en_NZ
uow.identifier.article-noARTN 011917en_NZ


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