Type III intermittency: a nonlinear dynamic model of EEG burst suppression.
Burst suppression electroencephalograms from 9 comatose patients have been studied using nonlinear dynamic techniques. These EEG records show many dynamical features characteristic of nonlinear systems, including sensitive dependence on initial conditions, self-organization, similarity across scales, and intermittency. Histograms of burst durations showed an asymmetric distribution with a decreasing tail of increasing duration. Interpreting the histograms from the standpoint of intermittency classifications of iterated dynamical maps, the absence of any conspicuous maximal cut-off duration suggests a type III intermittency. The power-law exponent of the decreasing tail is -3/2 for type III intermittency in the large scale sample size limit, and we have found the EEGs to be consistent with type III intermittency behavior. We have also developed a nonlinear algorithm which models burst suppression pattern based on a low dimensional return map. Burst suppression pattern appears to be the constrained activity of a nonlinear dynamical system at the transition to chaos.
Rae-Grant
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AD
Neurophysiology Laboratory, Lehigh Valley Hospital, Allentown, PA 18103.
Kim
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YW
D000293:Adolescent; D000328:Adult; D000368:Aged; D001921:Brain / Q000503:physiopathology*; D002648:Child; D002675:Child, Preschool; D003128:Coma / Q000503:physiopathology*; D004569:Electroencephalography; D006801:Humans; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D013997:Time Factors