Changes in Evoked Cortical Electrical Activity at Different Time Points after Warning and Target Stimuli

Changes in the low- and high-frequency oscillations of the EEG α-band in the intervals between meaningful visual stimuli

“…The EEG spectral power was averaged in all the EEG derivations, which was followed by the analysis of the low and high frequency α rhythm subband values. The regional dif ferences in the synchronization/desynchronization of the α band cortical potentials were studied earlier [12]. They confirmed the data available in the literature.…”

“…This mechanism allows the human brain to opti mally use this time factor in the processes of cortical processing of information upon the action of sequen tially acting meaningful external stimuli and the organi zation of response activity. We observed the timing of α rhythm desynchronization to the time period directly preceding a meaningful stimulus in experiments in which a subject solved a visuospatial task where the time interval between the warning and target stimuli in dif ferent series was 2 or 9 s [12]. According to numerous data in the literature, we consider this timing of α rhythm desynchronization an indicator of an increase in the functional activity of the cortex, its pre paredness for solving a cognitive task (an indicator of covert attention [13] and expectant attention [14,15]).…”

Induced Synchronization of the Alpha Rhythm During the Pauses Between Visual Stimuli with Different Levels of Cognitive Set Plasticity

“…1 show that at the set formation stage (when all subjects correctly recognized the difference in the emotional facial expressions in all 15 trials), a desynchronization reaction was seen during the first second after presentation of the target stimulus (S1), this affecting both the low-frequency and high-frequency components of the α rhythm to the same extents, in the "no errors" group of subjects and in groups with larger numbers of errors. This reaction was weaker in subjects with relatively small numbers of errors (1)(2)(3)(4)(5).…”

“…

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.

…”

“…Recognition of Facial Expression at the Set Testing Stage Using Different Pauses between Meaningful Visual Stimuli*Results for pauses of 1.6 and 8 sec from[4].…”