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ENTROPIES OF THE EEG: The effects of general anesthesia .

ENTROPIES OF THE EEG: The effects of general anesthesia. J. W. Sleigh 1 , E. Olofsen 2 , A. Dahan 2 , J de Goede 3 & A Steyn-Ross 4 .

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ENTROPIES OF THE EEG: The effects of general anesthesia .

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  1. ENTROPIES OF THE EEG: The effects of general anesthesia. J. W. Sleigh1, E. Olofsen2, A. Dahan2, J de Goede3 & A Steyn-Ross4. Department of Anaesthesia1, Waikato Hospital, Departments of 2Anaesthesiology and 3Physiology, Leiden University Medical Centre, Leiden, The Netherlands, and Department of Physics4, University of Waikato, Hamilton, New Zealand sleighj@hwl.co.nz

  2. Rationale: Why bother with EEG Entropy Estimators? • The formation and dissolution of cortical microstates = ‘Corticodynamic’ entropy • Limitation of microstates lower entropy • Lower entropyunconsciousness QUESTIONS (1) Is the EEG telling us about the Cortex? (2) Are Entropy Estimators wrecked by artifacts?

  3. Spectral Entropies Spectral Entropy (1:47Hz) Renyi Entropies Kullback-Leibler (=Relative entropy) CUP Fisher I Wavelet HOS Tallis (q) Embedding / Phase-space Entropies = Kolmogorov-Sinai Approximate Entropy and Cross ApEn Singular Value Decomposition Entropy Entropy Bestiary

  4. Patient data: Induction of Anesthesia Spectral Entropy Renyi: GSE ApEn (m=2) ApEn (m=5) DFA SVDen

  5. (Q). Why are the entropy estimators “sort-of-the-same” but “sort-of-different”? (A). See how they perform with controlled “PseudoEEG” signals • 1) AR2 model • 2) White noise + artifacts • 3) Real EEG + oscillations

  6. (1) Pseudo-EEG series (AR2) (1) Decreased by shift to Low-frequency power and Oscillations. < ??EXCEPT DFA ??> (2) ApEn(m=5) and ApEn(m=10) go the opposite direction to ApEn(m=2). ApEn(m=2) ApEn(m=5)

  7. (2) Are the differences just sensitivity to artifact? ApEn SVDen GSE Spectral Entropy Change in Entropy estimator Raw ‘pseudoEEG’ Series Magnitude of Artifact

  8. (3) The effects of oscillations: Patient data Spectral Entropy ApEn Difference in Parameter (raw-osc) DFA SVD en Value of parameter

  9. Conclusions... • (1a) Anesthetics “make the EEG less free”... • (1b) The EEG changes  Corticodynamic entropy... • (2a) Entropy estimators  Correlation-Time estimators...[DFA; ApEn(m=2)  ApEn(m=5)] • (2b) Sensitivity to artifacts  to underlying EEG signal...[SEN>GSE>SVDen,ApEn]

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