Rearing by foster Wistar mother with high level of maternal care counteracts the development of genetic absence epilepsy and comorbid depression in WAG/Rij rats.

It has been shown for the first time that rearing by a foster Wistar mother with high level of maternal care (MC) counteracts the expression of genetic absence epilepsy (AE) and comorbid depression - reduces the number, duration and index of spike-wave discharges (SWDs) and immobility time in the forced swimming test, as well as exerts substantial effects on morphology and time-frequency dynamics of SWDs in WAG/Rij rats. It is supposed that increases in MC early in development might be used to counteract epileptogenesis and comorbid depression in people genetically predisposed to AE.

Compensatory Changes in the Brain Dopaminergic System of WAG/Rij Rats Genetically Predisposed to Absence Epilepsy.

Involvement of the brain dopaminergic system in the age-related dynamics of absence epilepsy in WAG/Rij rats was examined by histological, immunohistochemical, and electrophysiological (EEG) methods. We revealed reduced expression of dopamine receptors in various brain structures prior to first manifestations of the disease (at the age of 1-3 months), reduced density of neurons in the center of nigrostriatal system (substantia nigra pars compacta) in 10-month-old rats in comparison with 1-month-old rats, and positive correlation between neural density in the substantia nigra and intensity of epileptic activity in EEG. It is hypothesized that loss of dopaminergic neurons and reduced nigrostriatal dopaminergic innervation of the brain could prevent the development of absence epilepsy in WAG/Rij rats.

[FREQUENCY-TEMPORAL STRUCTURE OF HUMAN ELECTROENCEPHALOGRAM IN THE CONDITION OF ARTIFICIAL HYPOGRAVITY: DRY IMMERSION MODEL].

Frequency-temporal electroencephalogram (EEG) reactions to hypogravity were studied in 7 male subjects at the age of 20 to 27 years. The experiment was conducted using dry immersion (DI) as the best known method of simulating the space microgravity effects on the Earth. This hypogravity model reproduces hypokinesia, i.e. the weight-bearing and mechanic load removal, which is typical of microgravity. EEG was recorded by Neuroscan-2 (Compumedics) before the experiment (baseline data) and at the end of day 2 in DI. Comparative analysis of the EEG frequency-temporal structure was performed with the use of 2 techniques: Fourier transform and modified wavelet analysis. The Fourier transform elicited that after 2 days in DI the main shifts occurring to the EEG spectral composition are a decline in the alpha power and a slight though reliable growth of theta power. Similar frequency shifts were detected in the same records analyzed using the wavelet transform. According to wavelet analysis, during DI shifts in EEG frequency spectrum are accompanied by frequency desorganization of the EEG dominant rhythm and gross impairment of total stability of the electrical activity with time. Wavelet transform provides an opportunity to quantify changes in the frequency-temporal structure of the electrical activity of the brain. Quantitative evidence of frequency desorganization and temporal instability of EEG wavelet spectrograms may be the key to the understanding of mechanisms that drive functional disorders in the brain cortex in the conditions of hypogravity.

[The analysis of fMRT answer's individual variability at healthy examinees when opening eyes, motor and speech tests].

This paper analyzes the variation of the functional anatomy of the brain in healthy people performing identical activities on the basis of functional magneticresonance imaging (fMRI). According to the authors, this approach allows you to showcase a variety of individual strategies to achieve the same external (behavioral) result intracerebral different means, and to identify the factors that determine this diversity. Investigated hemodynamic (fMRT) brain reactions at activization of attention to opening of eyes, motor (search of the right and left hand fingers) and speech tests (mental transfer of months or days of the week upside-down) at 21 healthy subjects (21-30 years): 14 men, 7 women. Certain variety of fMRT answers is revealed: 3-4 jet types of hemodynamic changes were allocated for test in group, and the percent of supervision of each type fluctuated from 40 to 10%. Shown marked gender differences responses which specificity is determined by the nature of the functional load. In motor and speech tests, performed with his eyes closed, fMRI response in women is characterized by greater specificity and locality than in men. At motor tests fMRT answers of men are accompanied big, than at women, inclusion in reaction of frontal areas of the cortex, providing realization of regulatory functions. When opening of eyes the women's fMRT responses, on the contrary, become more diffusion, and men's--more local.

[EEG-correlates of consciousness recovery after traumatic brain injury].

The aim of studies of patients in long-term posttraumatic unconscious state (PUS) was to outline prognostically significant EEG-markers of consciousness condition and an assessment of its dynamics orientation. We analysed outcomes of dynamic (from days to 16 years after trauma) EEG studies in 196 patients in TBI-caused PUS and different degrees of mental recovery: from chronic unconscious state up to clear consciousness. These results were compared to clinical protocols and data of MRI. It is revealed that dynamic features of EEC pattern (with the analysis of equivalent dipolar sources of separate components) allow to characterize the severity of patient's current state, to reveal the brain structures with the most expressed dysfunction, to define a zone of local cortical damage, and also the general direction of development of a traumatic illness (as though dynamics of a homeostasis of a brain). Frequency characteristics of EEG power spectrum (average frequency--an effective frequency strip) in a background and at reactions find the greatest predictive importance, especially at their assessment in 2-3 months after a trauma. The background interhemispheric EEG coherence (first of all, frontal) as the integrative characteristic of system brain activity, and its change at reactions to external incentives most reflect degree of consciousness oppression, dynamics and potential of its restoration. It was shown the high informational of the researches EEG changes to indifferent and functionally significant signs for an assessment of CNS functionality, and also of PUS pathogenesis.

[Age-related changes in behavior, in monoamines and their metabolites content, and in density of D1 and D2 dopamine receptors in the brain structures of WAG/Rij rats with depression-like pathology].

Behavior in the light-dark choice, open field, sucrose consumption/preference and forced swimming tests, monoamines and their metabolites content in 5 brain structures (prefrontal cortex, nucleus accumbens, striatum, hypothalamus, hippocampus), and density of D1- and D2-like dopamine receptors in the prefrontal cortex, nucleus accumbens and ventral tegmental area were studied in WAG/Rij rats at age of 36 days, 3 and 6 months. It has been found that with age, as far as spike-wave discharges aggravate, behavioral symptoms of depression (enhanced immobility in the forced swimming test, reduced sucrose consumption/preference) as well as a hypo-function of the mesolimbic dopaminergic brain system increase in WAG/Rij rats. At age of 36 days, when phenotypic expression of absence epilepsy in WAG/Rij rats is absent, neurochemical alterations in the brain suggesting a hypo-function of the mesolimbic dopaminergic system (deficit of dopamine in the nucleus accumbens), as well as symptoms of depression-like behavior, are not detected. In WAG/Rij rats, as well as in control rats, density of D1-like dopamine receptors in the nucleus accumbens decreased with age. A tendency to a lower density of D1-like dopamine receptors was found in WAG/Rij rats compared with controls at age of 3 months. In contrast with control rats, in WAG/Rij rats, density of D2-like dopamine receptors in the nucleus accumbens increased with age. Higher density of D2-like dopamine receptors was observed in WAG/Rij rats compared with controls only at age of 6 months when a hypo-function of the mesolimbic dopaminergic bran system was extremely pronounced indicating that this increase is a compensatory response to a deficit of dopamine.

[Comparison of event-related potentials components characteristics obtained during stimulation of symbolical and alphabetic matrixes used in brain-computer interface paradigm].

In order to create a brain-computer interface (BCI) on the basis of paradigm P300 (the so-called Farwell-Donchin paradigm, FD) with a symbolical matrix used as stimuli, there were compared characteristics of event-related potentials (ERP) obtained from stimulation both by symbolical and alphabetical matrixes. The matrixes contained 6 x 6 signs (cyrillic letters or symbols-pictograms). Nine healthy adults were examined in 18 experiments during which 28 channel EEG were recorded while matrixes of two types (containing either cyrillic letters or symbols-pictograms) were used for stimulation. The obtained ERP data, i.e. amplitudes and peak latencies of the following components of ERP: N1, P3 with sub-components P3a and P3b, N4 were compared and analized for different types of the stimulation matrixes. Similar changes in amplitude or peak latency received from 7 or more out of 9 examinees were taken into consideration, matching the criteria of significance. It was discovered that for components P3a, P3b and N4 the amplitudes of ERP in response to a symbolic matrix were bigger than to a letter matrix, the opposite being true for component N1. Latent periods of ERP components were shorter for a symbolic matrix than for a letter matrix in case of components N1 and P3a, and longer in case of P3b and N4. In order to find out which zones of the brain react to stimulation the most, there was conducted a pair t-test (series of pair t-tests) to analize the topography of variety of ERP responses to different types of stimuli, and, through comparing the amplitudes of ERP components, a topographical map detailing the variety of responses to the different types of matrixes was obtained. The data about the differences were analized separately for each of 28 channels, then the (absolute magnitude t-test) were summed up algebraically for all the nine examinees. Thus, it was shown, for amplitudes of all the tested ERP components in the case of pair "significant-insignificant letters", the topography of the t-test is represented by two separate areas with distinct lateralization. In the case of pair "significant-insignificant symbols", the field of maximum responses streanch in croas direction. In the case of pair "significant letters-significant symbols" the topography is elaboratly orgenised.

[Recognition of visual objects under forward masking. Effects of cathegorial similarity of test and masking stimuli].

In 38 healthy subjects accuracy and response time were examined during recognition of two categories of images--animals andnonliving objects--under forward masking. We revealed new data that masking effects depended of categorical similarity of target and masking stimuli. The recognition accuracy was the lowest and the response time was the most slow, when the target and masking stimuli belongs to the same category, that was combined with high dispersion of response times. The revealed effects were more clear in the task of animal recognition in comparison with the recognition of nonliving objects. We supposed that the revealed effects connected with interference between cortical representations of the target and masking stimuli and discussed our results in context of cortical interference and negative priming.

[Psychological and stabilographic features in healthy persons performing dual tasks with different quality].

The results of performance of 40 healthy volunteers (29.8 ± 2.47 y.o.) in four dual tasks that included postural balance task as a motor sub-task and calculation as a cognitive sub-task were compared to results of individual psychological assessment which measured working and spatial memory capacity, speed of attention switch etc. Performance of participants in dual tasks was not uniform. For each of four tasks four types of performance were observed. Those included decrease of performance in both or one task and increase of performance in both tasks. In one of the four dual tasks 30% of the group of participants performed in both components of dual task better then in separate motor and cognitive tasks. Better performance in this dual task correlated with higher speed of attention switch, higher estimates of spatial and working memory. Analysis of results of psychological and stabilografic investigations showed negative correlation between speed of sway of center of pressure (CoP) and speed of attention switch test, and also between amplitude of CoP sway along frontal axis and capacity of spatial and working memory. These correlations reflect involvement of cognitive resources in voluntary postural control and motor automatism in successful dual task performance. Selected variant of dual task could be used as an instrument of selection of individuals for activities related to high informational loads.

[Neurochemical mechanisms of depression-like behavior in WAG/Rij rats].

Behavior in the light-dark choice, open-field, sucrose consumption/preference and forced swimming tests, monoamines and their metabolites level in 6 brain structures (prefrontal cortex, nucleus accumbens, striatum, hypothalamus, hippocampus, amygdala), and density of D2-like dopamine receptors in 21 brain regions were studied in WAG/Rij and Wistar rats. WAG/Rij rats exhibited symptoms of depression-like behavior such as increased immobility in the forced swim test and decreased sucrose consumption/preference (anhedonia). Substantial changes in behavior indicating increased anxiety in WAG/Rij rats were not revealed. Neurochemical abnormalities suggesting hypofunction of the mesolimbic dopaminergic brain system were found in "depressive" WAG/Rij rats compared with "normal" Wistar rats: decreased levels of noradrenaline, dopamine, 3,4-dihydroxyphenylacetic acid, 3-methoxytyramine in the nucleus accumbens, and increased density of D2-like dopamine receptors in the nucleus accumbens and ventral tegmental area. Reduced levels of dopamine were also observed in the prefrontal cortex and striatum. No substantial changes in the content of monoamines and their metabolites have been revealed in the hypothalamus, hippocampus and amygdala as well as in the content ofserotonin and its metabolite 5-hydroxyindolacetic acid in all studied brain structures with the exception of increased level ofserotonin in the amygdala. Results suggest that hypofunction of the mesolimbic dopaminergic brain system (nucleus accumbens) is a neurochemical mechanism of depression-like behavior in WAG/Rij rats.

[Higher mental functions and cognitive auditory event-related potentials impairment in liquidators of Chernobyl accident].

An integrated neuropsychological study and analysis of cognitive auditory event-related potentials (ERP) using the three-stimulus oddball paradigm was performed in ten subjects who participated in the liquidation of Chernobyl accident and ten healthy subjects. Impairment of higher mental functions, including aspontaneity, fatigability, a decrease in the auditory-verbal and visual memories, and higher motor function deficiency was shown in liquidators. A decrease of amplitude in all components of ERP (N1, N2 and P3) was found in liquidators for all stimuli in both experimental situations (audition of all stimuli and counting of deviant stimuli) compared to healthy subjects. The latent period (LP) of ERP in liquidators was decreased for N1 and N2 components and increased for P3. The largest between-group differences in the LP were revealed in the frontal areas for N1 and P3 in the left hemisphere and for N2 - in the right one. The correlation analysis between the ERP and a neuropsychological study had shown that changes in the LP of N1 are correlated to the impairment of short-term memory and pose praxis of the right hand while changes in the N2 were correlated to the impairment of long-term memory and pose praxis of the left hand. The changes in LP of P3 were correlated to complex cognitive processing disorders. Thus, the complex study identified the deceleration of perception, processing, and analysis of information combined with the weakened inhibition and "uneconomical" type of reactivity which led to the impairment of higher mental functions in liquidators compared to healthy subjects of the same age. The changes found in liquidators are similar to those observed in elderly people and support the hypotheses on accelerated brain ageing caused by low dose irradiation.

[Comparison of reactive EEG changes and fMRI characteristics of brain health based on multivariate statistics].

To gain a deeper insight into the relationship between the electrogenesis and oxygenation of the brain, fMRI and EEG reactions to identical functional loads (opening of the eyes and right- and left-hand fingering) were compared in 11 young right-handed healthy subjects with statistical techniques. Changes in power, frequency and coherent EEG parameters obtained by 18-channel monopolar recording were compared with values of + BOLD-fMRI response, calculated for 18 corresponding cortical areas on the basis of application of the "virtual cap" by the original algorithm. In reactive changes of both hemodynamic and bioelectrical parameters, sets of independent factors were identified, which were regarded on the basis of their topography as specific (localized in the cortical representation ofa relevant analyzer) and nonspecific (diffuse and similar under different functional loads). Specific component dominated in the fMRI response, whereas non-specific component was characteristic of the EEG reaction. The similar topography of reactive fMRI and EEG factors under normal conditions, confirmed by the correlation analysis, reflects the multilevel character of the systemic organization of the brain activity, visualized, in particular, in the sagittal projections of the individual fMRI images. Each of the reactive EEG factors included all of the EEG quantitative characteristics. EEG coherence, which dominated among other parameters (with a local increase in the cortical representation of a relevant analyzer and a diffuse decrease in the areas of the influence of the regulatory structures) displayed the highest correlation with hemodynamic responses of the brain.

[Functional effects of transcranial electromagnetic stimulation (60 and 70 Hz) of the brain of intact rats and rats with acute brainstem damage].

Behavior and brain electrical activity of 79 male Wistar rats (intact and with acute experimental brainstem injury) were studied during the course of therapeutic transcranial electromagnetic stimulation (TEMS) with frequencies 60 and 70 Hz. In intact animals this effect was accompanied by a decrease in voluntary motor activity and increase in synchronization of the brain electrical activity, in particular, in the delta and beta1 frequency ranges. This inhibitory effect was similar to that of sleep. In the early period of acute experimental stem pathology, the TEMS course was accompanied by suppression of EEG signs of adaptive post-operative stress response and could lead to increased severity of the condition of an animal, along with the slowing of postoperative recovery. Cytomorphological evidence was obtained to the importance of vascular factor in the formation of cerebral reactions to TEMS.

[Sleep deprivation effect upon spatial memory consolidation in rats after one-day learning in a Morris water maze].

The effect of sleep deprivation by 'carousel' method on spatial memory consolidation in a Morris water maze was studied in Wistar male rats after one-day learning (in accordance to a protocol by Frick et al., 2000). It was found that after fast 3-hr learning the memory trace retains during 24-hr. Twenty four hour sleep deprivation followed learning impaired consolidation of spatial memory. So the rat model of a one-day learning is suitable for the studying of neurophysiological mechanisms of sleep deprivation effects on spatial memory consolidation.

[Does antiabsence drug ethosuximide exert antidepressant effect?].

Antiabsence drug ethosuximide (300 mg/kg/day in drinking water for 17 days) produced an antidepressant effect (a decrease in immobility time in forced swimming test) only in WAG/Rij rats genetically predisposed to absence epilepsy only at age of 5 months when spike-wave discharges well pronounced. On rats without spike-wave discharges (21-day-old WAG/Rij and Wistar rats at the age of both at 21 day and 5 months), ethosuximide didn't produce the antidepressant effect but tended to increases the immobility time and significantly decreases the number of divings (active behavior oriented to escape from stressful situation). Ethosuximide didn't substantially change the anxiety level in WAG/Rij rats but significantly enhanced anxiety in 21-day-old Wistar rats. The results suggest that ethosuximide is not possessed of antidepressant potential unrelated to its suppressive effect on spike-wave discharges.

[Method for estimation of ERP topography instability degree and its application in the experimental task of target letter discrimination].

A new method for estimation of human event-related potential (ERP) topography instability was developed. It was applied to the visual ERPs evoked in the experimental task of target letter discrimination. Periods of stable topography corresponding to the main ERP waves and those of unstable topography between them were revealed. Dependence of stability and instability characteristics on relevance of stimuli was disclosed: mean ERP magnitude (potential field power) of stable periods and duration of N1-P3a unstable interval were higher for target letters than for nontarget ones. Possible mechanisms of these effects are discussed.

[Receptive fields of detectors of bar and cross-like figures in classical and combined mapping].

Excitatory and inhibitory zones of receptive fields (RF) of detectors of cross-like figures and bars were studied in a primary visual cortex of cats under conditions of classical and combined mapping. Factor and correlation analysis demonstrated that detectors of bars and crosses differ in those interrelations, which are formed between the basic characteristics of neurons and their RF in each of group. The factor analysis of these connections showed that variables with the greatest weights, combined into the same factor, are different for different detectors. In detectors of bars, positive correlation was found between the background activity and weight characteristics of the RF excitatory and inhibitory zones. In detectors of crosses, inhibition indices showed a positive correlation with sensitivity to this figure, characteristics of excitatory RF zone and the background activity. Enlargement of the additional excitatory zones of cross detectors in combined mapping was significantly greater than in bar detectors. Formation of the RF and orientation sensitivity of bar and cross detectors is discussed, with account made of the finding that the sensitivity to bars is mostly formed by direct excitatory connections, whereas sensitivity to cross-like stimuli is formed by direct and recurrent intracortical inhibitory connections between the nearby neurons.

[Features of cognitive audiory evoked potentials changes at participants of liquidation of chernobyl accident consequences the message II. the analysis of late component P300].

At 10 participants of liquidation of consequences of Chernobyl accident (middle age 50.5 +/- 4.0 years) and at 10 healthy persons (middle age 47.0 +/- 6.0 years) are performed complex neuropsychological examination and registration acoustical cognitive evoked potentials (EP) using odd-ball paradigms. Neuropsyhological research has revealed at liquidators disorders of the higher mental functions, such as aspontanity, decrease speech and a visual memory, and also deficit of higher motor functions. According to the analysis of amplitude-time characteristics of component P300 acoustical cognitive EP a decrease in amplitude of this component at liquidators in all areas of the brain, for both experimental situations for all stimulus in comparison with healthy persons the same age was revealed. At the analysis of latent period (LP) P300 at liquidators the most distinct increase was revealed in a situation of passive listening for all kinds of stimulus. The analysis of reactivity of LP in different experimental situations has shown that at healthy persons during passive listening had similar values for all kinds of stimulus, and an account situation the maximum values--for significant stimulus. For liquidators the type of reaction in the form of increase in LP values at the majority of stimulus in both experimental situations. The analysis of regional LP changes of component P300 has found out the maximum distinctions between groups in frontal area of the left hemisphere. Along with it at liquidators the type the reactions similar for all shown stimulus without dependence from their importance in comparison with norm is revealed "uneconomical, superfluous". It can testify about decreasing of attention and memory reserves and to promote disorder of the higher mental functions. The described of amplitude-time characteristics of component P300 of acoustical EP at liquidators EP can testify to delay of perception, processing and the information analysis in a combination to easing of inhibitory processes leading to the higher mental dysfunctions. The obtained data have similarity to people of old age, supporting a hypothesis about the accelerated ageing of a brain, and also about pathological development of processes of ageing as a result of influence of low doses of radiation.

[Specificity of auditory evoked potencials changes in participants of Chernobyl accident consequences: I. Analysis of early N1 component].

Amplitude-time characteristics analysis of the N1 component of auditory cognitive evoked potentials (EP) was made in 10 persons who had participated in the cleanup of the Chenobyl Accident - liquidators (mean age 50.5 +/- 4.0 years old) and in 10 healthy subjects (mean age 47 +/- 6.0 years old). Comparison of amplitude features of the N1 auditory EP component in liquidators of the Chernobyl Accident found a decrease in all areas of the cortex with the maximum decrease in the central and frontal leads, and also an inversion in reactive changes to stimuli of different significance in comparison to healthy subjects of the same age. The most distinct differences between the healthy subjects and liquidators of the Chernobyl Accident were found for time characteristics of the N1 component. They show a significantly smaller value of latent period (LP) for all stimuli and for all experimental tasks in comparison with healthy subjects and more distinct for a significant stimulus when persons counted these stimuli. Analysis of regional changes in LP of the N1 component found that liquidators, in comparison with healthy subjects, have maximal differences in the frontal area of the left hemisphere which were accompanied with inversion asymmetry of LP in this component. Less distinct changes were observed in the central area with relatively little damage in the parietal area. Detected changes in the amplitude-time characteristics of the N1 component of the auditory cognitive EP in liquidators of Chernobyl Accident can show an abnormality in primary attention and its reserves due to weakened inhibitory processes in comparison with healthy subjects, which has similarities of old age. The obtained data supports the hypothesis about the accelerated brain aging in liquidators of Chernobyl Accident as a result of low dosage radiation effects; however, it also allows the pathological development of the brain ageing due to the effects of radiation.

[Overlapping of optical answers for cross-like figures and oriented bars in the cats primary visual cortex].

For the first time by the optical method the population activity of neurons in cat primary visual cortex was observed simultaneously for detectors participating in analysis of first-order (orientation) and second-order (line intersection) features. The maps for cross-like figures and oriented single bars were compared. The comparative analysis allowed us to estimate the degree of overlapping of the activated regions and parts of cortex that were free from overlap. Overlapping zones provided the evidence for the fact that neuronal detectors for line intersections are located in the same neuronal columns as neurons detecting orientations. Differences were observed between maps for vertically oriented and oblique crosses. Those differences were pronounced not only in topography but also in degree of overlapping of activity zones. This may evidence on different contribution of neurons detecting basic and intermediate orientations.