EEG changes with unblocking of acoustic and visual sensory canals

Modally specific and supramodal components of EEG dynamics, related to involuntary reorientation of anticipatory attention from internal into external, were studied using unblocking of either visual or acoustic apparatus. EEG registration took place while the examinees were in the resting states: with opened eyes; with closed eyes; with closed eyes and inserted noise-protective earplugs. Averaged values of EEG power in each of the derivations and of EEG coherence in each of the derivation pairs were calculated for an every examinee and for each of the states. The estimations were done in delta, theta, alphal, alpha2, beta1, beta2, gamma frequency bands. The received results support an idea about manifestation of both supramodal and modally specific components in brain mechanisms of involuntary anticipatory attention. These results seem to be of certain interest for existing discussion on divergence and convergence between systemic mechanisms of visual and auditory attention.     

Effects of unstructured video exposure on EEG power in situations of forced attention and rest

Group 1 (N = 30) and Group 2 (N = 22) of healthy volunteers participated in the experiment. In both groups, the EEG was recorded in the state of rest with the eyes closed (REC); at rest with eyes open (REO); and during passively watching TV channel noises (white noise). EEG was also recorded in the state of forced visual attention: when counting colored symbols appearing on the screen (group 1) and when searching for an image of a real object in the noise (group 2). The averaged values of EEG power in each derivation were calculated for every subject and for each state in the Δ, θ, α₁, α₂, β₁, β₂, and γ frequency bands. The results demonstrate that the exposure to unstructured noninformative video noise may lead to significant changes in the EEG power in various frequency bands, with the most prominent changes taking place in the α₂ band. These changes are topically wide, reflecting systemic changes in the corresponding brain mechanisms, but are much less intense compared to the difference between the states of rest with the eyes open and closed.     

EEG differences between resting states with eyes open and closed in darkness

Transition from a resting state with eyes closed (REC) to a resting state with eyes open (REO) is associated with visible changes in EEG, which are traditionally considered to be a sign of reorganization of the brain’s activity in response to visual stimuli. The EEGs recorded in the REC and REO states in complete darkness, when the stimulatory effect of light to the eye’s retina was absent, were compared. Thirty healthy subjects participated in the study. EEG in the range of 1.5–50 Hz was recorded from nineteen zones of the head monopolarly. It was found that, under conditions of complete darkness, the REC and REO states significantly differed in their EEG spectral power and coherence in the Δ, θ, α₁, α₂, β₁, β₂ and γ frequency bands. Under experimental conditions, these changes in the EEG could not be induced by external influence to the visual system. Therefore, we suppose that they are correlates of the switching of involuntary preliminary attention from internally directed attention specific for the REC state to externally directed attention specific for the REO state.     

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.     

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.     

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.     

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.     

Electroencephalographic characteristics of cognitive-specific alerting attention in verbal learning: III. Localized characteristics of EEG spatial synchronization

Electroencephalograms (EEGs) were recorded in 19 standard derivations in 88 healthy subjects (students) in the state of rest with eyes open and during memorization (learning) of verbal bilingual semantic pairs (the Latin and Russian languages) and retrieval of information from memory (control). The estimates of EEG coherence in these states were compared for the following frequency bands: θ (4–7 Hz), α₁ (7–10 Hz), α₂ (10–13 Hz), β₁ (13–18 Hz), β₂ (18–30 Hz), and γ (30–40 Hz). Compared to the state of rest, the decrease in coherence in the pairs of derivations from the frontal and central cortical areas in all EEG frequency bands was the most pronounced for memorization, and the increase in coherence in the interhemispheric derivation pairs of the parietal-occipital region in most of the frequency bands was the most pronounced for retrieval. In addition, in the pairs formed by derivations from the parietal-occipital region with derivations from the frontal and central regions, retrieval is also characterized by an increase in coherence in the β₂ and γ bands along with its decrease in the low-frequency ranges. The dynamics of EEG coherence, when comparing the states of memorization and retrieval, is more statistically significant in the interhemispheric and cross-hemispheric pairs of derivations than in the intrahemispheric pairs. The revealed topographic specificity of the dynamics of EEG coherence owing to the change of state is considered in terms of the notion on cognitive-specific forms of sustained goal-directed mental attention.     

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.     

Physiological significance of P2X receptor-mediated vasoconstriction in five different types of arteries in rats

P2X₁ receptors, the major subtype of P2X receptors in the vascular smooth muscle, are essential for α,β-methylene adenosine 5′-triphosphate (α,β-MeATP)-induced vasoconstriction. However, relative physiological significance of P2X₁ receptor-regulated vasoconstriction in the different types of arteries in the rat is not clear as compared with α₁-adrenoceptor-regulated vasoconstriction. In the present study, we found that vasoconstrictive responses to noncumulative administration of α,β-MeATP in the rat isolated mesenteric arteries were significantly smaller than those to single concentration administration of α,β-MeATP. Therefore, we firstly reported the characteristic of α,β-MeATP-regulated vasoconstrictions in rat tail, internal carotid, pulmonary, mesenteric arteries, and aorta using single concentration administration of α,β-MeATP. The rank order of maximal vasoconstrictions for α,β-MeATP (E _{max·α,β-MeATP}) was the same as that of maximal vasoconstrictions for noradrenaline (E _max·NA) in the internal carotid, pulmonary, mesenteric arteries, and aorta. Moreover, the value of (E _{max·α,β-MeATP}/E _max·KCl)/(E _max·NA/E _max·KCl) was 0.4 in each of the four arteries, but it was 0.8 in the tail artery. In conclusion, P2X₁ receptor-mediated vasoconstrictions are equally important in rat internal carotid, pulmonary, mesenteric arteries, and aorta, but much greater in the tail artery, suggesting its special role in physiological function.     

Adrenoceptors and signal transduction in neurons

The adrenergic system is an essential regulator of neuronal, endocrine, cardiovascular, vegetative, and metabolic functions. The endogenous catecholamines epinephrine and norepinephrine activate G-protein-coupled receptors to transmit their signal across the plasma membrane. These adrenoceptors can be divided into three different groups: the α₁-receptors (α_1A, α_1B, α_1D), α₂-receptors (α_2A, α_2B, α_2C), and β-receptors (β₁, β₂, β₃). This review summarizes recent findings in the field of adrenoceptor signaling in neurons and includes a discussion of receptor-associated proteins, receptor dimerization, subcellular trafficking, and fluorescence optical methods for studying the kinetics of adrenergic signaling. Spatio-temporal imaging may become an important future tool for identifying the physiological significance of these complex signaling mechanisms in vivo. Gene-targeted mouse models carrying deletions in α₂-adrenoceptor have provided detailed insights into specific neuronal functions of the three α₂-receptor subtypes.     

Subunit Regulation of the Human Brain α1E Calcium Channel

The α₁ subunit coding for the human brain type E calcium channel (Schneider et al., 1994) was expressed in Xenopus oocytes in the absence, and in combination with auxiliary α₂δ and β subunits. α_1E channels directed with the expression of Ba²⁺ whole-cell currents that completely inactivated after a 2-sec membrane pulse. Coexpression of α_1E with α_2bδ shifted the peak current by +10 mV but had no significant effect on whole-cell current inactivation. Coexpression of α_1E with β_2a shifted the peak current relationship by −10 mV, and strongly reduced Ba²⁺ current inactivation. This slower rate of inactivation explains that a sizable fraction (40 ± 10%, n= 8) of the Ba²⁺ current failed to inactivate completely after a 5-sec prepulse. Coinjection with both the cardiac/brain β_2a and the neuronal α_2bδ subunits increased by ≈10-fold whole-cell Ba²⁺ currents although coinjection with either β_2a or α_2bδ alone failed to significantly increase α_1E peak currents. Coexpression with β_2a and α_2bδ yielded Ba²⁺ currents with inactivation kinetics similar to the β_2a induced currents, indicating that the neuronal α_2bδ subunit has little effect on α_1E inactivation kinetics. The subunit specificity of the changes in current properties were analyzed for all four β subunit genes. The slower inactivation was unique to α_1E/β_2a currents. Coexpression with β_1a, β_1b, β₃, and β₄, yielded faster-inactivating Ba²⁺ currents than currents recorded from the α_1E subunit alone. Furthermore, α_1E/α_2bδ/β_1a; α_1E/α_2bδ/β_1b; α_1E/α_2bδ/β₃; α_1E/α_2bδ/β₄ channels elicited whole-cell currents with steady-state inactivation curves shifted in the hyperpolarized direction. The β subunit-induced changes in the properties of α_1E channel were comparable to modulation effects reported for α_1C and α_1A channels with β₃≈β_1b > β_1a≈β₄≫β_2a inducing fastest to slowest rate of whole-cell inactivation. Received: 27 March 1997/Revised: 10 July 1997     

Polymorphism of T-cell receptor genes among laboratory and wild mice: Diverse origins of laboratory mice

Southern blots of genomic DNA from 23 strains of laboratory mice and 19 individual wild mice were examined for restriction fragment length polymorphisms in their loci encoding the T-cell receptors (Tcr): the constant regions of the α, β, and γ chains (C _α,C _β, andC _γ) and a variable region family of the β chain (V _β8). Only a few polymorphisms were observed for each locus in the laboratory mice after using three restriction enzymes,Bam HI,Eco RI, andHind III. All the laboratory mice examined fall into one of two types for theC _α,C _β andV _β8 loci and one of three types for theC _γ. These types are found in some of the wild mice studied, indicating that they were already present in the founder mice of laboratory mouse strains. In contrast, theTcr genes are highly polymorphic among wild mice. Analysis of the polymorphisms in these loci suggests that laboratory mice have inherited their genes not only fromMus musculus domesticus, but also from other subspecies, and much more than previously believed from Asian subspecies.     

Probing functional interfaces of rod PDE γ-subunit using scanning fluorescent labeling

In the dark, the activity of the rod cGMP phosphodiesterase (PDE) catalytic α- and β-subunits (Pαβ) is inhibited by two γ-subunits (Pγ). On light stimulation of the photoreceptor cells, the GTP-bound α-subunit of visual G-protein transducin (G_taGTP) displaces the Pγ-subunits from their inhibitory sites on Pαβ, leading to the effector enzyme activation. We designed a number of Pγ mutants, each with a single cysteine residue evenly distributed at a different position along the Pγ polypeptide chain. These cysteine residues served as sites for the introduction of the environmentally sensitive fluorescent probe, 3-(bromoacetyl)-7-diethyl aminocoumarin (BC). Analysis of the interactions of Pαβ and G_ta with the fluorescently labeled Pγ mutants suggests two distinct functional interfaces of Pγ. The Pαβ/Pγ interface is formed essentially by the C-terminus of Pγ and by the N-terminal portion of the Pγ polycationic region, Pγ-24-45, whereas the Pγ/G_ta interface includes the C-terminal portion of Pγ-24-45 and the region surrounding Pγ Cys68. Such functional organization of Pγ may represent an important element for the PDE activation mechanism during transduction of visual signals.     

Scaling and organization of electroencephalographic background activity and alpha rhythm in healthy young adults

The coexistence of the broad-band fluctuation and α rhythm of the brain dynamics is studied based on the zero-crossing property of the local electroencephalographic (EEG) recording in eyes closed and eyes open. A two-component zero-crossing scenario, consisting of a broad-band fractal and narrow-band rhythm components, is assumed. Scaling is found in the power law distribution p(τ) ~ τ ^−ν of the crossing time interval τ of the broad-band fluctuation. In α dominant brain state, the α rhythm interval L also exhibits scaling in the form of power law distribution: . Our main result is the relationship that characterizes the organization of these two prominent features of the brain dynamics. The possible role of self-organized criticality of punctuated equilibrium in this organization is discussed.     

Marsupial cardiac myosins are similar to those of eutherians in subunit composition and in the correlation of their expression with body size

Cardiac myosins and their subunit compositions were studied in ten species of marsupial mammals. Using native gel electrophoresis, ventricular myosin in macropodoids showed three isoforms, V ₁, V ₂ and V ₃, and western blots using specific anti-α- and anti-β-cardiac myosin heavy chain (MyHC) antibodies showed their MyHC compositions to be αα, αβ and ββ, respectively. Atrial myosin showed αα MyHC composition but differed from V ₁ in light chain composition. Small marsupials (Sminthopsis crassicaudata, Antechinus stuartii, Antechinus flavipes) showed virtually pure V ₁, while the larger (1–3 kg) Pseudocheirus peregrinus and Trichosurus vulpecula showed virtually pure V ₃. The five macropodoids (Bettongia penicillata, Macropus eugenii, Wallabia bicolour, M. rufus and M. giganteus), ranging in body mass from 2 to 66 kg, expressed considerably more α-MyHC (22.8%) than expected for their body size. These results show that cardiac myosins in marsupial mammals are substantially the same as their eutherian counterparts in subunit composition and in the correlation of their expression with body size, the latter feature underlies the scaling of resting heart rate and cardiac cross-bridge kinetics with specific metabolic rate. The data from macropodoids further suggest that expression of cardiac myosins in mammals may also be influenced by their metabolic scope.     

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.     

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.     

Nickel Block of a Family of Neuronal Calcium Channels: Subtype- and Subunit-Dependent Action at Multiple Sites

Nickel ions have been reported to exhibit differential effects on distinct subtypes of voltage-activated calcium channels. To more precisely determine the effects of nickel, we have investigated the action of nickel on four classes of cloned neuronal calcium channels (α_1A, α_1B, α_1C, and α_1E) transiently expressed in Xenopus oocytes. Nickel caused two major effects: (i) block detected as a reduction of the maximum slope conductance and (ii) a shift in the current-voltage relation towards more depolarized potentials which was paralleled by a decrease in the slope of the activation-curve. Block followed 1:1 kinetics and was most pronounced for α_1C, followed by α_1E > α_1A > α_1B channels. In contrast, the change in activation-gating was most dramatic with α_1E, with the remaining channel subtypes significantly less affected. The current-voltage shift was well described by a simple model in which nickel binding to a saturable site resulted in altered gating behavior. The affinity for both the blocking site and the putative gating site were reduced with increasing concentration of external permeant ion. Replacement of barium with calcium reduced both the degree of nickel block and the maximal effect on gating for α_1A channels, but increased the nickel blocking affinity for α_1E channels. The coexpression of Ca channel β subunits was found to differentially influence nickel effects on α_1A, as coexpression with β_2a or with β₄ resulted in larger current-voltage shifts than those observed in the presence of β_1b, while elimination of the β subunit almost completely abolished the gating shifts. In contrast, block was similar for the three β subunits tested, while complete removal of the β subunit resulted in an increase in blocking affinity. Our data suggest that the effect of nickel on calcium channels is complex, cannot be described by a single site of action, and differs qualitatively and quantitatively among individual subtypes and subunit combinations. Received: 12 October 1995/Revised: 17 January 1996