Propofol Reversibly Attenuates Short-Range Microstate Ordering and 20 Hz Microstate Oscillations
Gesine Hermann1, Inken Tödt2, Enzo Tagliazucchi3
1Department of Neurology, Christian-Albrechts University, University Hospital Schleswig Holstein, Arnold-Heller-Strasse 3, 24105, Kiel, Germany.
Abstract:
Microstate sequences summarize the changing voltage patterns measured by electroencephalography, using a clustering approach to reduce the high dimensionality of the underlying data. A common approach is to restrict the pattern matching step to local maxima of the global field power (GFP) and to interpolate the microstate fit in between. In this study, we investigate how the anesthetic propofol affects microstate sequence periodicity and predictability, and how these metrics are changed by interpolation. We performed two frequency analyses on microstate sequences, one based on time-lagged mutual information, the other based on Fourier transform methodology, and quantified the effects of interpolation. Resting-state microstate sequences had a 20 Hz frequency peak related to dominant 10 Hz (alpha) rhythms, and the Fourier approach demonstrated that all five microstate classes followed this frequency. The 20 Hz periodicity was reversibly attenuated under moderate propofol sedation, as shown by mutual information and Fourier analysis. Characteristic microstate frequencies could only be observed in non-interpolated microstate sequences and were masked by smoothing effects of interpolation. Information-theoretic analysis revealed faster microstate dynamics and larger entropy rates under propofol, whereas Shannon entropy did not change significantly. In moderate sedation, active information storage decreased for non-interpolated sequences. Signatures of non-equilibrium dynamics were observed in non-interpolated sequences, but no changes were observed between sedation levels. All changes occurred while subjects were able to perform an auditory perception task. In summary, we show that low dose propofol reversibly increases the randomness of microstate sequences and attenuates microstate oscillations without correlation to cognitive task performance. Microstate dynamics between GFP peaks reflect physiological processes that are not accessible in interpolated sequences.
Insights
Low-dose propofol sedation reversibly reduces microstate sequence periodicity and increases randomness in electroencephalography (EEG) data. These effects, observed in non-interpolated sequences, highlight dynamics missed by interpolation.
Area of Science:
- Neuroscience
- Computational Neuroscience
- Anesthesiology
Background:
- Electroencephalography (EEG) microstate sequences analyze brain activity patterns.
- Global Field Power (GFP) and interpolation are common analysis methods.
- Propofol's effects on microstate dynamics require further investigation.
Purpose of the Study:
- To investigate propofol's impact on microstate sequence periodicity and predictability.
- To assess how interpolation affects these microstate metrics.
- To explore information-theoretic and frequency-domain changes under propofol sedation.
Main Methods:
- Performed frequency analyses (mutual information, Fourier transform) on microstate sequences.
- Quantified effects of interpolation on microstate periodicity.
- Utilized information-theoretic measures (entropy, active information storage) to analyze microstate dynamics.
Main Results:
- Resting-state EEG showed a 20 Hz microstate frequency peak linked to alpha rhythms.
- Propofol reversibly attenuated this 20 Hz periodicity, observable only in non-interpolated sequences.
- Propofol increased microstate dynamics' randomness and entropy rates, decreasing active information storage.
- Interpolation masked characteristic microstate frequencies and dynamics.
Conclusions:
- Low-dose propofol increases microstate sequence randomness and attenuates oscillations.
- These changes are independent of cognitive task performance.
- Non-interpolated microstate dynamics reveal physiological processes obscured by interpolation.
