Modulation of Low-Frequency EEG Rhythms under Conditions of an Activation Reaction: Dependence on Psychological Characteristics of Personality

In a group of 118 adults of both sexes, we studied modulation of the low-frequency EEG components (δ and θ rhythms) under conditions of an activation reaction resulting from opening of the eyes. Typical changes of the α 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 δ and θ components in different subjects. The δ 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 θ rhythm, the respective subgroups included 36, 75, and 7 subjects. Values of the differential coefficients of reactivity (DCR) for the δ and θ rhythms demonstrated significant positive correlation (r = 0.616 and 0.603 for the left and right hemispheres, respectively). Indices of reactivity of the α and θ 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 α and δ rhythms. Within the entire studied group, we found significant negative correlations between the DCRs of the δ and θ 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), OST (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 significant 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 δ and θ 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.     

EEG Correlates of the Psychological Adaptation Potential of a Personality

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.     

Peculiarities of EEG in Subjects with Coronary-Prone (Type A) Behavior

In a group including 72 adults of both sexes, we studied correlations between the estimates of the so-called coronary-prone personality type (type A) diagnosed using the Jenkins questionnaire and the spectral powers (SPs) of the frequency components (rhythms) of background EEGs recorded in the resting state (leads C3 and C4 according to the 10-20 system). Despite natural high interindividual variability, estimates that characterized the subject as belonging to the behavioral type A corresponded, on average, to relatively low SPs of the δ, θ, and α EEG components, intermediate values of the β₁ rhythm SP and coefficient of reactivity of the α rhythm, and higher SPs of the high-frequency (β₂ and γ) rhythms. Estimates characterizing type B personality corresponded to significantly higher δ-rhythm SPs, intermediate SPs of the θ and α rhythms, and smaller SPs of the β and γ rhythms. The interhemisphere asymmetry coefficient for the α rhythm was usually negative in type-A individuals and positive in the cases of types B and AB. The peculiarities observed are probably determined, to a certain extent, by the fact that both the characteristics of the behavioral types of the personality and the amplitude parameters of EEG rhythms depend significantly on inherited (in particular neurochemical) factors. Such peculiarities of the neurodynamic constitution of the individual are determined, to a considerable extent, by the specificity of organization and functioning of a few neurotransmitter (in particular aminergic) and neurohumoral systems.     

Modifications of the EEG frequency pattern in humans related to a single neurofeedback session

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 C3 and C4 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. Neirofiziologiya/Neurophysiology, Vol. 37, Nos. 5/6, pp. 443–451, September–December, 2005.     

Interrelations between Peculiarities of the Motivational Sphere of a Personality and Characteristics of the Current EEG

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 β₁ rhythms), low SPs of the β₂ 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. Neirofiziologiya/Neurophysiology, Vol. 41, No. 1, pp. 61–69, January–February, 2009.     

Modulation of High-Frequency EEG Rhythms under Conditions of the Activation Reaction: Dependence on Psychological Characteristics of Personality

In a group of 118 adults of both sexes, we studied modulation of high-frequency EEG rhythms (β and γ components) under conditions of EEG activation related to opening of the eyes. Typical changes in the α rhythm (significant depression in the overwhelming majority of the tested subjects) was accompanied by different (in direction and intensity) shifts of the spectral powers (SPs) of the β and γ components in different subjects. The power of the β1 subcomponent under conditions of the activation reaction increased in 6 persons and dropped in 109 persons; changes in this index in two hemispheres were opposite in their directions in 3 subjects. Thus, changes in the β1 SP upon opening of the eyes were nearly parallel to those of the α rhythm but less intense. The subgroups differentiated according to the pattern of reactivity of the β2 subcomponent included 23, 85, and 10 subjects; for the γ rhythm, the corresponding numbers were 31, 72, and 8. In other words, the patterns of reactivity of β2 and γ oscillations were rather similar to each other but differed significantly from the pattern for the β1 rhythm. Values of the differential coefficients of reactivity (DCRs) of the β1, β2, and γ rhythms demonstrated significant correlations that were especially close for the β2 and γ activity. Within the entire examined group, we found significant negative correlations of the DCR values for β and γ activities with the estimates of some psychological characteristics of the subjects (levels of neuroticism, psychoticism, plasticity, self-control of behavior, and some others) measured using the RTS (Strelau), EPQ (Eysenck), OST (Rusalov), and 16PF (Kettel) questionnaires. The dispersion analysis demonstrated that the above-mentioned subgroups of the subjects (with increase and decrease in the SPs of the β and γ rhythms in both hemispheres and opposite changes of these indices in the right and left hemisphere) showed significant or close to significant specific intergroup differences of a few mean values of the psychological characteristics estimated according to the above questionnaires. Possible mechanisms of modulation of high-frequency EEG components under conditions of the reaction of EEG activation and relations of such changes to the psychological characteristics of the personality are discussed.     

Spectral power of θ and α-EEG bands in preschool children with different levels of visual set plasticity

The spectral powers (SPs) of the θ and α EEG rhythms were studied at different stages of visual set in children from five to seven years of age. Children with a plastic set had a greater α band SP than those with a rigid set. At the set formation stage, children with a rigid set displayed an increase in the SP of the θ band, which is a manifestation of an “immature” activation reaction. Children with a plastic set exhibited an increase in the α band SP in the occipital lobes of both hemispheres. The dynamics of the SP of the EEG rhythms differed in children younger and older than six years. At the set formation stage, children from five to six years of age exhibited the above-mentioned “immature” activation reaction, while those from six to seven years of age showed an increase in the α band SP in the occipital lobes. At the set actualization stage, an increase in the α band SP was observed in the right caudal areas, while the set extinction stage was marked by a bilateral depression of the α band in the frontal lobes. The importance of the involvement of specific cortical areas in visual perception and the formation of a plastic set is discussed.     

Changes in EEG Rhythms and Spike Activity of Brainstem Dopaminergic Neurons Induced by Neurofeedback Sessions in Cats

We examined the dynamics of the ratios of spectral power densities (SPDs) of the alpha vs theta rhythms (α/θ ratio). of EEG and of the spiking frequency of supposedly dopaminergic (DA) neurons of the ventral tegmentum in the course of neurofeedback sessions directed toward changes in the EEG characteristics. Trainings were performed using techniques analogous to that used in neurofeedback sessions in humans. The level of the noise acoustic signal presented to the animal decreased with increase in the α/θ ratio in the occipital leads. In the control realizations, there were no dependences between the intensity of the acoustic signal and modulation of the current EEG. It was found that the animals learned, in a conditioned-reflex mode, to correlate changes in the intensity of the sound signal and power of the EEG rhythms and to control the latter; a high sound intensity was probably considered a factor of discomfort. The α/θ ratio in the course of neurofeedback sessions changed due to some increase in the SPD of the alpha EEG component and a noticeable drop in the SPD of theta oscillations. In a parallel manner with such modifications, augmentation of the spike activity of DA neurons was observed. Probable mechanisms of the involvement of the cerebral DA system in the formation of the effects of neurofeedback sessions are discussed.     

Characteristics of EEG reactivity changes during the performance of dual tasks in healthy subjects (voluntary postural control and calculation)

Comprehensive EEG and stabilography investigation with separate and simultaneous performance of motor (voluntary postural control) and cognitive (calculation) tasks has been performed in 20 healthy subjects (22 ± 0.7 years). Specific spatial and frequency reactive changes have been found during motor task performance. These included an increase in coherence in the EEG α band for distant derivation pairs in the right hemisphere, as well as in symmetric parietal-occipital areas in both hemispheres. Cognitive task performance was accompanied by an increase in coherence for the slow bands (δ and θ) with a higher activation in the left hemisphere and frontal cortex areas. In performing the dual task, one could observe activation of spatial and frequency changes including both motor and cognitive tasks. In the dual tasks where both components were performed worse as compared to the control, reactive reorganization of EEG coherence was less pronounced than during the performance of separate tasks. A decrease in the coherence of the α₁ band in the frontal areas appeared as a zone of “conflict of interest” or interference. In dual tasks with better performance of each component as compared to the control, EEG coherence increased in each specific area, as well as in the areas of “conflict of interests.”     

Modulation of EEG Rhythms and Changes in Spike Activity of Noradrenergic Neurons of the <Emphasis Type="Italic">Locus Coeruleus</Emphasis> Related to Feedback Sessions by EEG Characteristics

In chronic experiments on awake cats, we studied the dynamics of the spectral power density (SPD) of the α rhythm vs SPD of the θ rhythm ratio and also of the characteristics of impulse activity generated by supposedly noradrenergic (NA) neurons of the locus coeruleus in the course of feedback (FB) sessions by EEG characteristics (EEG-FB). Trainings were performed using a technique analogous to that in EEG-FB sessions for humans. The level of a sound noise signal presented to the animal decreased with increase in the α/θ SPD ratio in the occipital lead. Changes in the level of the sound signal did not depend on EEG modulation in the control series. The animals were trained to correlate changes in the loudness of the sound signal with the power of EEG rhythms and, in such a way, to control the latter. The α/θ SPD ratio in EEG-FB sessions changed mostly due to a significant increase in the α rhythm power. The frequency of the impulse activity of NA neurons increased in a parallel manner with such EEG modulation. Possible mechanisms of the involvement of the cerebral NA system in the formation of the effects of EEG-FB sessions are discussed.     

The relationships between EEG θ and β oscillations and the level of creativity

The interrelations between the level of creativity and both the baseline power and event-related desynchronization/synchronization (ED/ES) of θ and β rhythms during a figural creative task (Torrance’s “Incomplete Figures” test) were studied under the conditions of different motivations. A higher motivation was caused by instruction “to create most unique images” as opposed to the instruction “to create images.” The subjects, right-handed students (14 males and 14 females), were divided into two groups with high and low originality scores (OSs). The baseline power and the ED/ES of the θ₂ and β rhythms of the subjects were found to depend on the level of creativity and person’s sex only in response to the instruction “to create images.” Male subjects with higher OSs differed from those with lower OSs in a stronger ED of the θ₂ rhythm in temporal-parietal-occipital brain regions, whereas these differences were absent in female subjects. Task performance was accompanied by ED of β₁ rhythm in men with higher OSs, whereas in women with higher OSs, ES was recorded in the same band. Only in women with high OSs did analysis of β_{1, 2} reference power show a higher β₁ power in the caudal hemispheric regions as compared to the frontal ones. High-OS subjects of different genders also differed in the lateral patterns of activity in the electrode loci Fp_1/2 (β₁) and Fp_1/2, F_7/8 (β₂). Our results suggest that a high level of creativity in men and women is related to sex-dependent specific patterns of frontal-occipital and lateral activities of θ and β rhythm oscillators in the brain cortex.     

The Moral Aesthetics of Simulated Suffering in Standardized Patient Performances

Standardized patient (SP) performances are staged clinical encounters between health-professional students and people who specialize in role-playing the part of patients. Such performances have in recent years become increasingly central to the teaching and assessment of clinical skills in U.S. medical schools. SP performances are valued for being both “real” (in that they involve interaction with a real person, unlike written examinations) and “not real” (in that the SP does not actually suffer from the condition portrayed, unlike an actual patient). This article considers how people involved in creating SP performances reconcile a moral commitment to avoid suffering (to keep it “not real”), with an aesthetic commitment to realistically portray it (to keep it “real”). The term “moral aesthetic” is proposed, to indicate a sensibility that combines ideas about what is morally right with ideas about what is aesthetically compelling. Drawing on ethnographic research among SPs and SP program staff and medical faculty who work closely with them, this article argues that their work of creating “realism” in simulated clinical encounters encompasses multiple different (and sometimes conflicting) understandings and practices of realism, informed by three different moral aesthetics: (1) a moral aesthetic of induction, in which an accurate portrayal with a well-documented provenance serves to introduce experientially distant forms of suffering; (2) a moral aesthetic of inoculation, in which the authenticity and emotional impact of a performance are meant to inoculate students against the impact of future encounters with suffering; (3) a moral aesthetic of presence, generating forms of voice and care that are born out of the embodied presence of suffering individuals in a clinical space. All are premised on the assumption that risk and suffering can be banished from SP performances. This article suggests, however, that SP performances necessarily raise the same difficult, important, fundamentally ethical questions that are always involved in learning from and on human beings who are capable of suffering, and who need and deserve recognition and respect as well as care.     

Correlation between the Activity of Dopaminergic Neurons of the Ventral Tegmentum and Spectral Power of the EEG Rhythms in Awake Cats

We studied correlations between the frequency of background impulse activity (BIA) of dopaminergic (DAergic) neurons of the ventral tegmentum (VT) and spectral power (SP) of the frequency components of EEG samples recorded in awake cats. The EEG was recorded monopolarly (electrodes were fixed in the cranial bones) from the frontal, occipital, and right and left temporal regions of the cortex. In a great majority of the cases, the BIA frequency of VT DA-ergic neurons demonstrated significant positive correlations with changes in the SPs of the alpha and beta EEG rhythms. The closest correlations of the spiking frequency of DA-ergic cells with the SP of the alpha rhythm was observed in the occipital region, while those with the beta SP were found in the frontal area. Correlations of the activity of DA-ergic neurons with the SPs of the alpha and beta rhythms in the left temporal cortical zone were closer, as compared with those in the symmetrical right zone. Correlations of the SPs of the delta, theta, and gamma EEG components with the discharge frequency of VT DA neurons were of opposite directions, and in most cases such correlations did not reach the level of significance. The results of this study show that, in some cases, specific EEG patterns can be considered indicators of the state of the cerebral VT DA-ergic system. Neirofiziologiya/Neurophysiology, Vol. 40, No. 4, pp. 359–367, July–August, 2008.     

Spectral Characteristics of the EEG in Students with Different Levels of Result Achievement under the Conditions of Examination Stress

The EEG correlates of the performance of examination tests and special cognitive tests under the conditions of everyday study (common studying conditions, CSCs) and immediately before examination (examination conditions, ECs) were analyzed in 39 male students aged 18–20 years. The results of the examinations strongly correlated with the relative spectral power (SP) of the EEG rhythm before the examination. Therefore, the students were divided into two groups with different directions of changes in the -range SP under the ECs compared to the CSCs. Students from group 1 were characterized by increased relative - and -rhythm SPs under the ECs and a good examination performance; students of group 2, by decreased - and -rhythm SPs, an increased index of the EEG of the central and frontal cortical regions under the ECs, and a poor examination performance.     

Locus of Psychological Control and Characteristics of the EEG Frequency Components

In a group including 65 adults of both sexes, we examined correlations of the internal/external personality type (locus of psychological control diagnosed by the Rotter questionnaire) with parameters of the EEG frequency components (rhythms). Multichannel recording of ongoing EEG was carried out in the resting state; leads were located according to the 10-20 system. Despite natural high interindividual variability, the subgroup of internals was, in general, characterized by higher spectral powers (SPs) of the δ, θ, α, and β1 rhythms and a lower SPs of β2 and γ oscillations recorded in the resting state with the eyes closed. In internals, the modal frequencies of practically all EEG ranges were, on average, somewhat lower. In this subgroup, reaction of EEG activation related to opening of the eyes was stronger, while the interhemisphere asymmetry was weaker.     

Dynamics of EEG potentials at the beginning of a series of EEG-feedback sessions

We studied changes in the amplitudes of event-related EEG potentials (ERPs) and power spectra of background EEG in the course of a series of EEG-feedback sessions directed toward an increase in the ratio of powers of the α vs θ rhythms. The examined group included 70 volunteers divided into an experimental group (n = 37) and a control group (n = 33). The intensity of acoustic white noise overlapping the musical background served as a feedback signal; it became lower with increase in the above ratio, while in the control group it remained constant. The EEG potentials were recorded from C3 and C4 leads. The ERPs were recorded within a paradigm of measuring time intervals. Within a series of EEG-feedback sessions, the α/θ ratio decreased somewhat both in the control and experimental groups, but in subjects of the latter group this decrease was less significant, and the mean intragroup index became significantly greater than the respective value in the control group after the end of the third session. The EEG-feedback sessions also resulted in significant increases in the amplitudes of early components of the readiness potential in both hemispheres and in the amplitude of the contingent negative variation in the right hemisphere. We conclude that, in most healthy subjects, at least three sessions of α/θ training are necessary to form an effective series providing considerable changes in the pattern of EEG potentials. Neirofiziologiya/Neurophysiology, Vol. 39, No. 1, pp. 88–98, January–February, 2007.     

Allosteric serine hydroxymethyltransferase from monkey liver: Correlation of conformational changes caused by denaturants with the alterations in catalytic activity

The far-ultraviolet region circular dichroic spectrumof serine hydroxymethyltransferase from monkey liver showed that the protein is in an α-helical conformation. The near ultraviolet circular dichoric spectrum revealed two negative bands originating from the tertiary conformational environment of the aromatic amino acid residues. Addition of urea or guanidinium chloride perturbed the characteristic fluorescence and far ultraviolet circular dichroic spectrum of the enzyme. The decrease in (θ)₂₂₂ and enzyme activity followed identical patterns with increasing concentrations of urea, whereas with guanidinium chloride, the loss of enzyme activity preceded the loss of secondary structure. 2-Chloroethanol, trifluoroethanol and sodium dodecyl sulphate enhanced the mean residue ellipticity values. In addition, sodium dodecyl sulphate also caused a perturbation of the fluorescence emission spectrum of the enzyme. Extremes of pH decreased the — (θ)₂₂₂ value. Plots of — (θ)₂₂₂and enzyme activity as a function of pH showed maximal values at pH 7.4–7.5. These results suggested the prevalence of “conformational flexibility” in the structure of serine hydroxymethyltransferase.     

Modulation of attention in healthy children using a course of EEG-feedback sessions

We studied changes in the power spectra of EEG in the course of sessions of feedback by EEG characteristics (neurofeedback sessions) and estimated the effects of neurofeedback on psychological and EEG correlates of voluntary attention. Indices of the latter were estimated using Bourdon’s test (a correcture test) and Schulte’s tables. Twenty-nine reasonably healthy 10-to 13-year-old children took part in the study; they were divided into two groups, an experimental group (n = 12) and a control group (n = 15). The results obtained support the statement on noticeable changes in the functional state of the brain both immediately in the course of a neurofeedback session and after a course of such trainings. Changes in the ratios of the spectral powers of the beta₁ vs theta rhythms and the low-frequency beta vs theta rhythms were found in EEG recorded from the sensorimotor zone of the right hemisphere (C4). The observed changes in the spectral characteristics of EEG induced by the course of neurofeedback sessions were accompanied by the improvement of a few indices of voluntary attention. Neirofiziologiya/Neurophysiology, Vol. 38, Nos. 5/6, pp. 458–465, September–December, 2006.     

Background cerebral electrical activity in healthy mental aging

EEG power mapping in the frequency bands from Δ to γ₂ was used to study the changes in the background cerebral activity during “successful” cognitive aging, with the cognitive ability preserved, in subjects engaged in complex occupational activities. The sample consisted of an older age group (OAG) of 32 subjects (14 men and 18 women with a mean age of 65.1 ± 1.18 years) and a younger age group (YAG) of 33 subjects (18 men and 15 women with a mean age of 22.1 ± 0.38 years). The mean power of the slow (Δ, θ, and α₂) rhythms decrease with age, and that of the fast (β and γ) rhythms increase with age. The heterogeneity of the power parameters recorded at different sites was decreased in the OAG compared to the YAG. The centro-lateral power gradient was smoothed in the frequency bands from Δ- to β₂-, and both the centro-lateral and fronto-parietal power gradients and interhemispheric differences, in the α- and β₁ bands in the OAG. The results suggest that the observed age-related changes are prerequisites for the involvement of compensatory mechanisms, which may be related to both mobilization of larger resources ensuring cognitive activity and reorganization of cortical networks in the areas prone to age-related physiological changes.     

Wavelet entropy in event-related potentials: a new method shows ordering of EEG oscillations

 In this work we show the application of a measure of entropy defined from the wavelet transform, namely the wavelet entropy (WS), to the study of event-related potentials (ERPs). WS was computed for ERPs recorded from nine healthy subjects with three different types of stimuli, among them target stimuli in a cognitive task. A significant decrease of entropy was correlated with the responses to target stimuli (P300), thus showing that these responses correspond to a more “ordered” state than the spontaneous EEG. Furthermore, we propose the WS as a quantitative measure for such transitions between EEG (“disordered state”) and ERP (“ordered state”). Received: 12 April 2000 / Accepted in revised form: 11 September 2000