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Loss of Consciousness Is Associated with Stabilization of Cortical Activity

Here are the Supplementary Materials to our J. Neurosci. paper. 

 

Video captions. 
 

ECoG signals are recorded as a monkey  is induced into anesthesia with ketamine and medetomidine. We fitted AR(1) models to the data in windows of 300 ms taken every 1 seconds. We tracked changes in the distributions of the eigenvalues of the fitted models, by measuring departures from the initial distribution at t=0.  The paper's main result is that loss of consciousness is coincidental with an overall increase of damping of the fitted dynamics. 

First row: We used Kolmogorov-Smirnov statistical test to tracks changes in the dynamical stability of VAR models fitted to ECoG recordings. The distributions were clustered into five groups by a k-means algorithm indicated by symbols.  
 
Second row, first three panels:  Distributions of damping and mode frequency for the shaded intervals. These were sampled in intervals of 300 secs (5 mins), indicated by the shaded regions in (first row), number of bins is 50x50 and N=O(4).  
 

Second row, fourth panel:  Distributions overlay. Make sure to scroll the video to  easily visualize changes in the distributions.

Fourth row: For each eigenvector (ev) we defined the entropy' as S(ev) = norm1(ev) / norm2(ev) * sqrt(N) and built the distributions for the shaded regions. 

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 M4-Propofol.mp4

 M4-Ketamine Medetomidine

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For more details check our previous frontiers paper http://journal.frontiersin.org/article/10.3389/fncir.2014.00020/abstract which contains the same analysis performed in human subjects undergoing anesthesia with propofol. 

 

 

 

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