Open Access Research article

Cross-approximate entropy of cortical local field potentials quantifies effects of anesthesia - a pilot study in rats

Matthias Kreuzer1, Harald Hentschke23*, Bernd Antkowiak2, Cornelius Schwarz34, Eberhard F Kochs1 and Gerhard Schneider1

Author Affiliations

1 Department of Anesthesiology, Klinikum rechts der Isar, Technische Universität München, München, Germany

2 Section of Experimental Anaesthesiology, University Hospital Tübingen, Tübingen, Germany

3 Department of Cognitive Neurology, Hertie-Institute for Clinical Brain Research, University Tübingen, Tübingen, Germany

4 Werner Reichardt Centre for Integrative Neuroscience, University Tübingen, Tübingen, Germany

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BMC Neuroscience 2010, 11:122  doi:10.1186/1471-2202-11-122

Published: 23 September 2010

Additional files

Additional file 1:

Figure S1A depicts the dose response relationships of XApEn for the same data as used in Figure 5, but filtered with an upper cutoff frequency of 30 Hz and resampled at 100 Hz. Same conventions as for Figure 5 apply, including monoexponential fits represented by solid lines. Qualitatively, the same observations as with the original data set, containing frequencies up to 200 Hz, can be made: decline of XApEn with anesthetic concentration, significant difference between halothane on the one hand and enflurane and isoflurane on the other hand. However, the data are more variable among animals and show less decline with anesthetic frequency. The free parameter tau was [95% confidence intervals]: 2.37 [1.34 3.41] for isoflurane, 2.30 [1.50 3.10] for enflurane and 6.31 [4.67 7.94] for halothane. R2 values were 0.52, 0.68 and 0.51 (same order of agents). Figure S1B shows dose response relations of cross correlation values (normalized to control) computed from the same data as used for Figure 5. While on average the cross correlation increased with anesthetic concentration, there was little dose dependence, and intra- and interindividual variability was extremely high (cf. Figure 3).

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