Desynchronization and synchronization of EEG related to stimuli triggering or forbidding sensory-motor reaction in adolescents: II. The peculiarities in case of the attention deficit and hyperactivity syndrome

Evoked desynchronization and synchronization of EEG in θ (4–7.5 Hz), α (7.5–14 Hz) and β (14–20 Hz) ranges were recorded by 19 electrodes in healthy volunteer adolescents and those with attention deficit hyperactivity syndrome in the modified GO/NO-GO test. Two stimuli (high and low tone) were presented in pairs with 1 s intervals inside the pair and 1.5 s intervals between the pairs. Test subjects had to push the button in response to presentation of a pair of high tones and to ignore other stimulus combinations. The components of evoked EEG synchronization in α-θ range that were revealed in the frontocentral and temporoparietal brain regions in connection with inhibition of action (inhibition of movements and making a decision to cancel sensory-motor task performance) were statistically significantly lower in subjects with attention deficit hyperactivity disorder compared with that in healthy subjects.     

Normative EEG spectral characteristics in healthy subjects aged 7 to 89 years

The EEGs of 885 healthy subjects of both sexes aged 7 to 89 years were recorded in two modes: with the subjects’ eyes closed and with the eyes open. The subjects were divided into 20 age groups, for each of which the normative values of the EEG spectral characteristics were determined: the total EEG power spectra and the EEG independent component power spectra in the Δ, ϑ, α, and β frequency bands. Tables of confidence intervals with a level of confidence of 0.95 were constructed for each electrode channel in the case of the EEG power spectra and for each component in the case of the EEG independent component power spectra. The normative values obtained may provide EEG specialists with objective criteria for assessing cerebral dysfunction.     

Success of the test task performance by students with different spectral α-rhythm characteristics in the baseline electroencephalogram

The subjects were divided into two groups according to the α₁ and α₂ spectral powers in the occipital derivations of the EEG recorded in the initial state with their eyes closed. Group I included subjects whose α₁-rhythm spectral power (7–10 Hz) was more than 70% of the total α-rhythm band power. Group II included subjects whose α₂-rhythm spectral power (10–13 Hz) was more than 70% of the total α-rhythm band power. It was established that, in the tasks requiring prediction of the subsequent result (memorizing a certain sequence of signals and its subsequent reproduction on the monitor screen), group I subjects differed from group II subjects in fewer sequence errors and a greater number of accurate predictions. In group II subjects, a decrease in the ϑ-band spectral power in the EEG of the central and frontal cortical areas was observed compared to the baseline. Therefore, the EEG ϑ-rhythm power at the memorizing stage was lower in them than in group II subjects. The results suggest that the baseline characteristics of ϑ-activity can be regarded as prognostic criteria of similar types of activity.     

Electroencephalograms of patients with initial signs of depression: Independent component analysis

Independent component analysis (ICA) of 19-channel background EEG was performed in 111 patients with the early signs of depressive disorders and in 526 healthy subjects. The power spectra of the independent components were compared in the depressive patients and in healthy subjects at the eyes closed and eyes opened states. Statistically significant differences between the groups were detected in three frequency bands: θ (4–7.5 Hz), α (7.5–14 Hz), and β (14–20 Hz). Increased θ and α activities in parietal and occipital derivations of depressive patients may have been caused by a reduced cortical activity in the projection of these derivation. Diffuse enhancement of the β activity may be correlated with anxiety symptoms that are pronounced in the clinical picture of depressive disorders at early stages of the disease. ICA used to compare quantitative EEG parameters in different groups of patients and in healthy persons makes it possible to localize the differences more accurately than the traditional analysis of EEG spectra.     

Reflection of the emotional experience, strength, intensity of drive and probability of its satisfaction in interhemispheric distribution of frequency-amplitude parameters of EEG

The character of interhemispheric distribution of frequency-amplitude parameters of EEG as a function of the strength of emotional experience, the intensity of drive, and the expected probability of its satisfaction were determined in human test subjects. The emotional state was aroused by an imaginary reproduction of emotionally colored events. The modified test by D. Price and co-authors was used where the subjects estimated the intensity of drive (the degree of undesirability of imaginary event) and the expected probability of its occurrence by the length of line segment. In this study, the simulation of anger was used. The highest correlation coefficients were observed between the expectation and power in the α-EEG-range in the left frontal region. The strength of emotional experience negatively correlated with the α-, θ-, and Δ-ranges. Statistically significant correlation was revealed between the intensity of drive and power of Δ- and θ-waves. The power of β-rhythm correlated with the strength of emotion as well as with the expectation and drive indices.     

Pharmacophores of the dual acting α, β-blockers as deduced,from molecular dynamics simulations

The dual acting α, β-blockers have an important place in the management of hypertension. Molecular dynamics simulations have been carried out on all stereoisomers of seven dual acting α, β-blockers namely adimolol, amosulalol, bucindolol, carvedilol, labetalol, medroxalol and primidolol. Three families of conformations have been identified for the group of compounds. The pharmacophores for α and β-activity have been constructed for two of these families.     

Training for voluntarily increasing individual upper α power as a method for cognitive enhancement

In order to estimate the effect of simultaneous α EEG stimulating and electromyogram (EMG) decreasing biofeedback training on the α activity and cognitive functions, fluency, accuracy, and flexibility during cognitive tasks, as well as α-activity characteristics before, during, and after ten training sessions of voluntarily increasing α power in an individual upper α range with the eyes closed were studied in 27 healthy men aged 18–34 years. To isolate the biofeedback effect in training for the α power increase, data on two groups of subjects were compared: an experimental group (14 subjects) with true biofeedback and a control group (13 subjects) with sham biofeedback. Follow-up testing was performed one month after the end of training to estimate the stability of the effect. The results showed that the training for the upper α power increase using biofeedback increased the frequency, width, and power in an individual upper α range at rest and improved cognitive performance only in subjects with a low baseline α frequency. Conversely, sham biofeedback training (without the feedback signal) increased the α power, though less efficiently, only in subjects with a high baseline α frequency, this increase was not accompanied by improved cognitive performance. The biofeedback α training eliminated the decrease in the α amplitude in response to a cognitive task after the biofeedback training course, this effect being preserved within one month. It may be concluded that α EEG-EMG biofeedback training can be used for improving cognitive processes in healthy subjects, as well as for prognostic purposes in clinical practice and in the brain-computer interface technology.     

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.     

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.”     

Effect of increasing running velocity on electroencephalogram in a field test

This study was designed to measure the electroencephalogram (EEG) after exercise with increasing intensity. In a field test with increments in running velocity a 2-min EEG was recorded, together with blood lactate concentration and heart rate, after each stage. An individual protocol was used, with up to six stages of running to ensure comparability of exercise intensity among the subjects, in each of 19 athletes (17 men, 2 women) experienced in leisure-time running. The exercise consisted initially of three running stages of aerobic exercise intensity without blood lactate accumulation followed by stages with an increase of lactate concentration. The protocol of the field test led to a progressive increase in cortical activity directly after the stages without blood lactate accumulation mainly in the δ frequency band, followed by θ and α-1 frequency band, and less pronounced in the α-2 and in the β frequency bands. After the stages with an onset and further increase of blood lactate accumulation significant decreases in the β-2, β-1 and α-1 frequency bands occurred predominantly in temporal (T3, T4, T5, and T6) and occipital (O1, and O2) electrode positions, indicating a stage-by-stage decrease of activity. This decrease may be explained by feed-back from working muscle, via afferents to the cortex from intero- and proprio-receptors and affective processes. This could suggest that through a higher running intensity indicated by an onset of blood lactate accumulation metabolic and mechanical changes led to alterations within the afferent systems influencing the level of cortical activity. Accepted: 9 February 1998     

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.     

EEG changes upon unblocking of the acoustic and visual channels

Modality-specific and supramodal EEG components that are related to the reorientation of involuntary anticipatory attention from the internal to the external type were studied by comparing the unblocking of the visual and acoustic channels. EEG recording was performed while subjects were at rest with their eyes open, with their eyes closed, or with their eyes closed while using noise-protective earplugs. The means of both the EEG power in each of the derivations and EEG coherence in each of the derivation pairs were calculated for every subject and for each of the states. The estimations have been done for the Δ, θ, α₁, α₂, β₁, β₂, and γ frequency bands. The obtained data proved the hypothesis on the manifestation of both modality-specific and supramodal components in the brain mechanisms of involuntary anticipatory attention. These results are of interest for discussion on the degree of similarity and distinction between the systemic supports of the brain mechanisms of visual and auditory attention.     

A comparative electrophysiological study of regulatory components of working memory in adults and seven- to eight-year-old children: An analysis of coherence of EEG rhythms

Coherence at the frequency of θ, α, and β EEG rhythms was analyzed in 14 adults and 23 children of 7–8 years old while they performed cognitive tasks requiring an involvement of working memory (WM). We used the pair matching paradigm in which subjects had to match a pair of stimuli shown in succession in the central visual field. The pairs of verbal and visuo-spatial stimuli were mixed together and presented in a pseudo random order. Each pair was preceded by a warning signal that did not specify a modality of upcoming stimuli. We analyzed EEG segments recorded (i) in the rest condition, (ii) prior to the first (reference) stimulus (maintenance of nonspecific voluntary attention), and (iii) prior to the second (test) stimulus (retention of information in WM). In the present study we focused on the regulatory functional components of WM, and therefore, the stimulus modality has not been taken into account. In adults, maintaining nonspecific voluntary attention was accompanied by an increase of the strength of θ-related functional coupling between medial areas of the frontal cortex and temporal cortical zones and by a strengthening of local β-related functional connectivity in the fronto-central areas of the cortex. In children, no such increase was found for θ rhythm; for β rhythm the increase was limited to several short-range functional links. In adults, the retention of information in WM was accompanied by the growth in α coherence in distant fronto-parietal links, predominantly in the right hemisphere, while in children information retention was accompanied by the growth of θ coherence in the inferio-temporal and parietal cortical regions. The results of the study point to a relative immaturity of the mechanisms of executive control of WM in children of 7–8 years old.     

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.     

The pivotal role of the β7 strand in the intersubunit contacts of different human small heat shock proteins

Human αB-crystallin and small heat shock proteins HspB6 and HspB8 were mutated so that all endogenous Cys residues were replaced by Ser and the single Cys residue was inserted in a position homologous to that of Cys137 of human HspB1, i.e. in a position presumably located in the central part of β7 strand of the α-crystallin domain. The secondary, tertiary, and quaternary structures of thus obtained Cys-mutants as well as their chaperone-like activity were similar to those of their wild-type counterparts. Mild oxidation of Cys-mutants leads to formation of disulfide bond crosslinking neighboring monomers thus indicating participation of the β7 strand in intersubunit interaction. Oxidation weakly affects the secondary and tertiary structure, does not affect the quaternary structure of αB-crystallin and HspB6, and shifts equilibrium between monomer and dimer of HspB8 towards dimer formation. It is concluded that the β7 strand participates in the intersubunit interaction of four human small heat shock proteins (αB-crystallin, HspB1, HspB6, HspB8) having different structure of β2 strand of α-crystallin domain and different length and composition of variable N- and C-terminal tails.     

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.     

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.     

An Approach to Prebiotic Synthesis of α-Oligoribonucleotides and Description of Their Properties: Selective Advantage of β-RNA over α-RNA

Oligomerization of α-adenosine 5′-phosphorimidazolide (α-ImpA) has been done in an aqueous solution using a uranyl-ion catalyst or a poly(U) template as a model process of prebiotic synthesis of RNA with α-glycosidic linkage. α-Oligoriboadenylates up to hexamer were formed from α-ImpA by the uranyl-ion catalyst. 3′-5′ Linkage was mainly formed in the oligomerization. The poly(U) template mediated the oligomerization of α-ImpA, but to a very low extent. The yield and chain length of the resulting α-oligomers were far lower than those of the corresponding β-oligomer formation under the same conditions. Physico-chemical properties of α-oligoriboadenylates are presented along with those of the corresponding β-oligoriboadenylates. The results indicate that β-RNA is more advantageous than α-RNA from the points of their synthesis and properties. Received: 10 February 1997 / Accepted: 31 March 1997     

Domain III function of Mu transposase analysed by directed placement of subunits within the transpososome

Assembly of the functional tetrameric form of Mu transposase (MuA protein) at the two att ends of Mu depends on interaction of MuA with multiple att and enhancer sites on supercoiled DNA, and is stimulated by MuB protein. The N-terminal domain I of MuA harbours distinct regions for interaction with the att ends and enhancer; the C-terminal domain III contains separate regions essential for tetramer assembly and interaction with MuB protein (IIIα and IIIβ, respectively). Although the central domain II (the ‘DDE’ domain) of MuA harbours the known catalytic DDE residues, a 26 amino acid peptide within IIIα also has a non-specific DNA binding and nuclease activity which has been implicated in catalysis. One model proposes that active sites for Mu transposition are assembled by sharing structural/catalytic residues between domains II and III present on separate MuA monomers within the MuA tetramer. We have used substrates with altered att sites and mixtures of MuA proteins with either wild-type or altered att DNA binding specificities, to create tetrameric arrangements wherein specific MuA subunits are nonfunctional in II, IIIα or IIIβ domains. From the ability of these oriented tetramers to carry out DNA cleavage and strand transfer we conclude that domain IIIα or IIIβ function is not unique to a specific subunit within the tetramer, indicative of a structural rather than a catalytic function for domain III in Mu transposition.     

Polar steroids from <Emphasis Type="Italic">Solaster endeca</Emphasis> starfish and the physiological activity of polar steroids from three starfish species

Four polyhydroxylated steroids, new (20R)-5α-cholestan-3β,6α,8,15α,24,26-hexaol (I) and known (20R,25S)-5α-cholestan-3β,6α,8,15β,16β,26-hexaol, (20R,25S)-5α-cholestan-3β,6α,15β,16β,26-pentaol, and marthasterone sulfate were isolated from the Solaster endeca starfish inhabiting the Sea of Okhotsk and characterized. Steroid (I) contains a 24,26-dihydroxylated side chain, which is unique for starfish polyols. The isolated steroids and related metabolites from two starfish species of the Evasterias genus (in total, 15 compounds) were weakly cytotoxic in a human HeLa cell culture and some of them were inhibitors of non-specific esterase from mouse Ehrlich carcinoma. The effects of these compounds on the p53 protein activity were studied in a yeast two-hybrid test system and both inhibitors and stimulators of this activity were found among them.