Abstract:Background and Objectives: Infra-slow oscillations of brain potentials with a frequency of less than 0.5 Hz, reflect the activity of the autonomic regulation centers and are markers of the psychophysiological state of a person. Such oscillations are characterized by non-stationary dynamics, which complicates their experimental study. Materials and Methods: We have proposed a method for estimating the characteristic time of stationarity of infra-slow oscillations of brain potentials based on the analysis of experimental time series of electroencephalograms. The method includes the stages of dividing the time series into segments, constructing approximating polynomials for each segment, calculating the matrix of Euclidean distances between the coefficients of the polynomials, clustering the segments to determine areas of quasi-stationary dynamics, and analyzing the durations of the combined segments to obtain statistical characteristics. The proposed method can be used to estimate the stationarity time of other electroencephalograms rhythms, as well as the frequency components of the sequence of RR-interval. The method was used to analyze electroencephalograms signals and RR-intervals of 50 healthy volunteers at rest. Results: It has been shown that oscillations in different frequency ranges of the studied signals have different durations of quasi-stationary behavior. In the frequency ranges of 0.05–0.15 Hz and 0.15–0.50 Hz, reflecting the activity of the sympathetic and parasympathetic branches of regulation, respectively, the stationarity time of infra-slow oscillations in electroencephalograms signals was 30 s and 36 s, respectively. Conclusion: The durations of quasi-stationary sections of infra-slow oscillations in electroencephalograms correspond well to the durations of sections of quasi-stationary dynamics of the sequence of RR-interval in the frequency ranges associated with the processes of sympathetic and parasympathetic regulation of the heart rhythm.
Fulltext:
PDF file (655 kB)