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Studies using models of cognitive sets (the Uznadze paradigm) for simple nonverbal visual stimuli or an emotionally negative facial expression have identified features of the dynamics of electrical oscillations in the range of the α rhythm in the cerebral cortex at specified periods of time between warning and target stimuli [4] or between target and trigger stimuli [3]. Both cases recorded the long-known rhythm desynchronization reaction in response to presentation of the first stimulus in the pair, but produced the first evidence that the middle part of the pause, conversely, involved synchronization, which then decreased notably or changed to desynchronization before presentation of the second stimulus in the pair. Working on the basis of current concepts, we regarded these changes in α activity over the 8-or 9-sec interstimulus time interval as induced reactions evoked by top-down spikes coming from the internal representation of time intervals between the acting stimuli formed in the prefrontal cortex during the training process [6,[10][11][12][13]18].α rhythm power in humans is known to be linked with the function of selective attention and to reflect its activity [7,8,15,19]. Thus, desynchronization of the α rhythm is regarded as an indicator of increased functional activity in the corresponding area of the cortex, its readiness to undertake some particular type of cortical activity, and as an indicator of "covert attention" [20] or "expectant attention" [16,17]. On the other hand, we regard the α-activity synchronization in the midpart of the interstimulus pause seen Studies in healthy adults (n = 35) using a model of a set to recognition of an angry facial expression showed that increases in loading on working memory by extending the duration of the time interval between the target (a facial image) and trigger (a spot of light) stimuli to 16 sec did not lead to any significant slowing of the switching from the old set to the new. Differences were seen between the group of subjects in whom set switching was accompanied by distorted perception of the emotional facial expression and the "no errors" group in the extents of the induced synchronization of the α rhythm during the interstimulus period. Synchronization was more marked in this latter group. The dynamics of changes in the α rhythm showed that selective attention was modulated during sequential cognitive acts, this being apparent at the bioelectrical level as changes in the extent of induced synchronization/desynchronization of α-range potentials. The proposed "inhibitory control" mechanism provides flexibility for cognitive processes by suppressing the influences of irrelevant factors on cortical processes during interstimulus pauses. We believe that this "protective" mechanism can explain the minor effect of increased loading on working memory in the present studies.

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