We studied changes in the frequency pattern of EEG related to a single session of biological feedback by the EEG characteristics (neurofeedback, NFB) directed toward an increase in the ratio of α/θ spectral powers (SPs) (an experimental group; 30 subjects) and to a session of the supposedly indifferent acoustic influence (listening to a musical background; 30 persons). A standard technique of EEG recording was used; the loudness of white noise overlapping the musical background served as an NFB signal. EEG was recorded from the С3 and С4 leads. Within the examined experimental group, an NFB session elicited a trend toward statistically insignificant decreases in the SPs of δ, α, and β rhythms and increases in the SPs of θ and γ EEG components. Listening to a supposedly neutral musical background by the control group, with no attempts at self-control of the SPs of EEG rhythms, was followed by rather clear unidirectional (partially significant) decreases in the SPs of θ, α, β, and γ components; the δ activity in the left hemisphere decreased, while in the right hemisphere it increased. In general, results of the single NFB session were characterized by a high interindividual variability, which can be related mostly to the specificities of psychophysiological characteristics of the personality of the tested subject.

In a group of 118 adults of both sexes, we studied modulation of the low-frequency EEG components ( and  rhythms) under conditions of an activation reaction resulting from opening of the eyes. Typical changes of the  rhythm (considerable depression in a great majority of the tested subjects) was accompanied by diverse, in their direction, shifts of the spectral power (SP) of the  and  components in different subjects. The  rhythm power increased upon the reaction of activation in 79 subjects and decreased in 29 subjects, while changes in this index in different hemispheres were of opposite directions in 10 persons. According to the reactivity of the  rhythm, the respective subgroups included 36, 75, and 7 subjects. Values of the differential coefficients of reactivity (DCR) for the  and  rhythms demonstrated significant positive correlation (r = 0.616 and 0.603 for the left and right hemispheres, respectively). Indices of reactivity of the  and  rhythms also correlated but less closely (r about 0.3). At the same time, there was practically no correlation between the DCR values of the  and  rhythms. Within the entire studied group, we found significant negative correlations between the DCRs of the  and  activity with the estimates of some psychological characteristics of the subjects (levels of extroversion, psychoticism, ergicity, plasticity, dominance, and a few others) measured using the questionnaires RTS (Strelau), EPQ (Eysenck), ОSТ (Rusalov), and 16 PF (Kettel). We also found positive correlations with the levels of normativity of behavior and development of imagination. At a rather high significance of such correlations, coefficients of the latter were, as a rule, relatively low (usually less than 0.2). Results of dispersion analysis showed that signifi cant or close to significant intergroup differences of the mean values of estimates of psychological characteristics diagnosed according to the above-mentioned questionnaires were typical of the subgroups of subjects with increases and decreases in the SPs of the  and  rhythms or with opposite changes of these indices in the hemispheres. Probable mechanisms of modulation of the low-frequency EEG components under conditions of the activation reaction and correlations of such changes with psychological peculiarities of the personality are discussed.

In a group of 70 adult subjects of both sexes, we estimated the levels of the need for achievement and its motivation (interpreted as generalized characteristics of the state of the motivational sphere of a personality and diagnosed using questionnaires of Orlov and Mehrabian) and examined the correlations of these estimates with spectral powers (SPs) of the frequency components (rhythms) of the current background EEG (С3 and С4 leads according to the 10-20 system). Despite the fact that naturally high interindividual variability exists, high estimates of the need for achievement correlated with medium values of the SPs of most EEG frequency components (δ, θ, α, and β 1 rhythms), low SPs of the β 2 and γ rhythms, and higher values of the coefficient of reactivity (CR) of the α rhythm. A high level of the need for achievement corresponded to higher SPs of the θ and γ rhythms and high CR of the α rhythm, a medium SP of this EEG component, and lower SPs of the δ and β rhythms. The coefficient of interhemisphere asymmetry of the α rhythm was the highest at low values of the studied psychological indices. Interrelations that we found in our study can be explained as follows: both the characteristics of the need for achievement and motivation typical of a certain personality and the amplitude parameters of the EEG rhythms observed in this individual depend significantly on genetically determined factors (in particular, on neurochemical ones). These peculiarities of neurodynamic constitution of the individual are, to a considerable extent, due to the specificity of organization and functioning of a few neurotransmitter (aminergic, in particular) and neurohumoral systems.

Modifications of different EEG rhythms induced by a single neurofeedback session (by the EEG characteristics) directed toward an increase in the ratio of the spectral powers (SPs) of the α vs θ oscillations were compared with the psychological characteristics of the tested subjects (the group included 30 persons). A generally accepted neurofeedback technique was used; the intensity of acoustic white noise served as the feedback signal. EEG potentials were recorded from the C3 and C4 leads. Psychological testing was carried out using Eysenck's (EPQ), Rusalov's (OST), and Сattell's (16 PF) questionnaires. The directions of changes in the SPs of EEG frequency components were found to significantly correlate with some individuality-related peculiarities of the tested subjects. The SP of the δ rhythm correlated with the EPQ scale "neuroticism," OST scale "social plasticity," and 16 PF factors H ("parmia"), I ("premsia"), and Q 3 ("self-control of behavior"). The SP of the θ component demonstrated correlations with the OST scales "ergisity," "plasticity," and "social temp" and with 16 PF factors M ("autia"), Q 4 ("frustration"), and Q1 ("exvia"). The SP of the α rhythm correlated with 16 PF factors Q 3 ("self-control of behavior"), G ("strength of superEgo"), O ("hypothymia"), L ("protension"), and N ("shrewdness"). The SP of the β rhythm correlated with the OST scale "emotionality," while that of the γ rhythm showed correlations with the 16 PF indices L ("protension") and M ("autia"). Changes in the ratio of the α vs θ SPs correlated with the EPQ scale "neuroticism." Thus, our data confirm the statement that a high individual variability of the results of a single (first in the series) neurofeedback session is to a great extent related to peculiarities of the individual psychological pattern of the subject.

In a group of 68 adults of both sexes, we examined correlations between estimates of the psychological adaptability of an individual (diagnosed using a multilevel personality questionnaire, MPQ) and spectral powers, SPs, of the frequency components (rhythms) of background EEG recorded in the resting state (leads C3 and C4 according to the 10-20 system). Despite high individual variability within the group, indices by the scale "communicative potential" demonstrated significant correlation with the SP of the θ rhythm, while estimates of the moral normativity correlated with the SPs of the α and β1 rhythms. Subgroups of the persons classified according to the level of the integral adaptation capability (personality's adaptation potential) differed from each other in the mean estimates of interhemisphere asymmetry of the α rhythm; this index was higher in subjects with the medium/high level of adaptability. The correlations observed are, most probably, determined by the fact that both the level of psychological adaptability of the personality and the EEG amplitude parameters depend significantly on genetic (neurochemical, in particular) factors. Such peculiarities of the neurodynamic constitution of the individual are probably determined, to a considerable extent, by the specificities of organization and functioning of a few neurotransmitter (aminergic, in particular) and neurohumoral systems.