Fluctuation of complex wavelet coefficients amplitude correlation in EEG

The paper is devoted to a novel method for detecting the back-loop regulation of coupling and decoupling between cortical neurones from electroencephalogram (EEG) signals. In this method, a linear time-scale quantifier of the multivariate relationship between simultaneously observed time series takes advantage of unique properties of complex wavelets such as shift invariance, substantially reduced aliasing and non-oscillating magnitude. The quantifier provides correlation between amplitude of complex wavelet coefficients for different frequencies (controlled by the scale factor) at different times (controlled by the time shift). Biological interpretation of this measure is derived from a priori information about presence of inhibitory back-loop connections between cortical neurones in short distance while the long range excitatory connections do not appear to target or effectively excite inhibitory interneurons and analysis of sample pairs of EEG signals.