Method of assessing the complexity in the brain spatial electrical activity
The paper describes the adaptation of the radiophysics traditional method to analyze the complex dynamics of systems with both spatial and temporal freedom degrees, namely the method of orthogonal decomposition of spatio-temporal data using the Karhunen-Loeve transform (KLT). KLT turns out to be very useful in the analysis of processes of various distributed systems in problems of hydrodynamics, plasma physics, microwave optics. Today there are few studies in which KLT is used to analyze the EEG of the cerebral cortex [Wongsawat, Yodchanan, Soontorn Oraintara, and K. Raghunath Rao. "Integer sub-optimal Karhunen-Loève transform for multi-channel lossless EEG compression." 2006 14th European Signal Processing Conference. IEEE, 2006; Klonowski, Wlodzimierz, et al. "Quantitative measure of complexity of EEG signal dynamics." Acta Neurobiologiae Experimentalis 59 (1999): 315-322]. However, these works apply KLT in a narrow sense, either to compress EEG signals, or to highlight significant physiological changes in biological systems, for example, epilepsy. However, the using of this method in the analysis of biophysical data can significantly expand the possibilities of interpreting the complex dynamics of a system from the point of view of the existence and interaction of coherent orthogonal space-time structures in it.
We use an adapted KLT to analyze the brain activity of adult subjects during the Multiple Sleep Latency Test. The use of KLT makes it possible to demonstrate the degree of complexity in EEG activity. These various stages with different EEG-complexity of the psychophysiological state of the test subject correlate with the assessment of the test subject's reaction time.
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Evgeniy N. Egorov
Saratov State University
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