<p num="82">FIELD: medicine.</p> <p num="83">SUBSTANCE: invention relates to medical technologies, namely electroencephalography, and can be used to studying brain bioelectric activity, designing brain-computer interfaces, determining and analyzing diagnostic parameters for post-stroke neurorehabilitation and diagnosing neurodegenerative diseases. Disclosed is a method of estimating power differences of oscillatory components of electroencephalogram (EEG) signals in psychophysiological conditions, including measurement and analysis of electroencephalogram components with subsequent mathematical processing, consisting in recording electroencephalograph signals in the first and second states of the test person, extracting a one-dimensional target signal from a multidimensional array of recorded EEG signals, selecting an envelope of narrow-band oscillations of the target signal for two states using narrow-band filtration of the selected target signal with subsequent calculation of the absolute value of the tim