[The nonstability of the EEG: a methodological and experimental analysis].

Theoretical, methodological and methodical aspects on nonstationary EEGs, that is, EEGs whose patterns undergo changes with time are reviewed. The piecewise description of the EEG is confirmed on the base of the own data and results of another investigators. It is analysed the basic approach to statistical evaluation of nonstationary EEGs in the terms of quasi-stationary segments. The special attention is devoted tho the data of segmental organization of the bioelectrical field of the cortex. Taking into consideration new experimental data concerning the time consistency of the segmental descriptions of regional EEGs it is suggested conception of "operational synchrony" as a form of discretial cooperation of cortex process. The theoretical explanations of the phenomenology for piecewise functioning of neuron nets are discussed.