Concerning the amplitude modulation of the human EEG

Amplitude-modulated processes can be formally presented as a product of two or more sinusoids. This makes it possible to study them by means of analysis of multiplicative phenomena using the Fast Fourier Transform (FFT). To assess the contribution of amplitude EEG modulation to the dynamic of electrical activity of the human brain, the results of the FFT of simulated signals obtained by multiplication of oscillatory processes with different parameters were compared with the results of the FFT of a single EEG recording from a subject at rest. We studied the temporal dynamics of spectral components calculated with different spectral resolution under similar conditions for real and simulated signals. An attempt was made to analyze and interpret the amplitude-modulated EEG processes using the additive properties of the FTT. It was shown that processes of amplitude modulation are present in electrical brain activity and determine the synchronism of changes in time in the majority of frequency components of the EEG spectrum. The presence of the amplitude modulation in bioelectrical processes is of a fundamental nature, since it is a direct reflection of the control, synchronization, regulation, and intersystem interaction in the nervous and other body systems. The study of this modulation gives a clue to the mechanisms of these processes.