The goal of the present study was to compare EEG power in frequency bands δ, θ, α1, α2, β1, β2, γ between such phases of a certain goal-directed behavior as a standby to perceive and solve verbal problems, perception proper and problem solving proper. Divergent and convergent kinds of verbal problems were used. 44 healthy examinees had undergone 19-channell monopolar EEG registration while carrying out the tasks and in a state of rest with eyes opened. Subject-averaged EEG power estimations were calculated for every situation of interest and in every of the aforementioned frequency ranges. Dispersion analysis ANOVA with within-subjects design was applied for the statistical analysis.
When the standby phase was compared to the rest state the power increase all over the cortex in β2, γ ranges and over anterior part of the cortex in β1 range could be seen. In the ranges δ, θ, α1, α2 the transition is accompanied with the power increase too but only in prefronal and foretemporal derivations. On the contrary a transition from standby to perception results in increase of low-frequency EEG power all over the cortex in ranges δ, θ and except frontal and central zones in a range α1. No significant differences could be seen in other frequency ranges. A transition from perception to the phase of problem-solving produced a variety of effects in all the frequency ranges except for γ.There were power increases for most of zones in δ range, the same except for occipital zones in θ,
increases in frontal zones and decreases in posterior zones in α1, decreases in central, parietal and occipital zones in α2 range. In ranges β1, β2 significant decreases were revealed in 10 and 8 derivations accordingly. Presumably it can be concluded that only high-degree cognitive activity demands systemic reorganizations in brain mechanisms of sustained attention, to great extent influenced by modality of information presentation. Thus in the experiment the potential to distinguish subdivisions of mental behavior using quasi-stationary EEG power was confirmed. It can be of importance in attempts to develop taxonomy of mental states on a base of objective electrophysiological indices.