[Cortical activation: the role of the indeterminacy/determinacy of a situation].

Ontogenetic data concerning EEG correlates of activation during attention were analysed in various paradigms. The results were compared with the degree of certainty/uncertainty of situation established by the instruction or determined by the subject. A proposition is made about two activation types in human EEG desynchronization and synchronization within the alpha-band. Both activation types which facilitate brain organization of present or forthcoming activity realize it in their own ways. Desynchronization which leads to disintegration of the system promotes formation of the new one. Synchronization immediately facilitates functional integration of brain structures involved into a specific form of activity. The results of processing and evaluation of information which characterize certainty/uncertainty of situation determine the balance between the two activation types.