[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.

[FMRI-EEG estimation of cerebral reactivity to motor tasks in patients with brain tumors].

fMRI (1.5 or 3 T) and EEG studies with estimation of reactive responses on motor task (by right or left hand) were performed in 9 patients with tumors localized in frontal lobe of the brain. Results of this investigation were compared with results of the similar study in 12 healthy persons. It was shown that in cases of the brain pathology disorders of functional specialization and increase of diffuse component of reactivity was observed, fMRI-responses had been characterized the more intact reactions than reactive changes of EEG parameters. This specificity was described in cases of afferent loads in damaged hemisphere. Peculiarity of including different spectral bands in forming of EEG responses on motor tasks and changes of fMRI-answer depend on degree of cerebral decompensation, reflected in the of baseline EEG reorganization and degree of motor defect. Predominantly an increase of EEG coherence in delta-band with the predominance of reaction in the damaged hemisphere in cases of addressing any afferent load was observed in patients with severe cerebral decompensation and reflect dominant character of pathological focus forming. This data indicate on the more including of the deep brain structures in process of reactivity in patients compared with healthy persons and confirmed by fMRI-data.

[Impairment of space-frequency parameters of EEG coherence during cognitive performance (consequences of Chernobyl accident)].

Changes in frequency and space parameters of the EEG coherence evoked by cognitive performance were analyzed in 13 healthy subjects and participants of the Chemobyl clean-up. In healthy subjects, the EEG coherences in the alpha and beta frequency bands were significantly increased during arithmetic count and during visuospatial performance. Each test was characterized by regionally-specific features. Chemobyl patients demonstrated a global decrease in the EEG coherence predominantly in the alpha and beta frequency bands, especially in the frontal cortical areas. Patients with various pathological EEG patterns demonstrated specific impairment of EEG parameters. In patients with a "flat" EEG pattern, the EEG coherence predominantly decreased in the frontal associative areas, especially during arithmetic calculation. In patients with a "hypersynchronous" EEG pattern, the decrease in the EEG coherence was most pronounced in the parietal associative areas, especially during the visuospatial performance. The revealed impairments of the EEG coherence reactivity may be a reflection of disorders of the intracortical and corticosubcortical interaction and can result from the remote postradiation brain atrophy, especially, of cortical structures.

[Mathematical analysis of EEG in consciousness recovery after traumatic brain injuries].

The clinical and EEG study of 20 patients with post-comatose consciousness disturbances caused by severe traumatic brain injuries (9 patients with autonomic state and 11 with Korsakoff syndrome), applying a statistical method of analysis of EEG spectrum and coherent connections developed by the authors, has revealed pathological features of the EEG interhemispheric connections. Patients with consciousness disturbances exhibited (1) total functional disconnections of hemispheres which was characteristic of the autonomic state and (2) disconnection in frontal areas of the brain in patients with Korsakoff syndrome as compared to the normal spatial distribution of coherence observed in 40 healthy people. Consciousness recovery has been accompanied by interhemispheric connections normalization, at first in the posterior regions of the hemispheres and then in the anterior ones as well as by transforming of coherence profile in the shape of "envelope" being most typical for the normal pattern of coherence distributation.

[Particular aspects of bioelectric brain activity in post-traumatic Korsakoff syndrome]. / Osobennosti bioélektricheskoi aktivnosti mozga pri posttavmaticheskom korsakovskom sindrome.

Thirty two patients, 21 with recurrent and 11 with chronic Korsakoff's syndrome of traumatic genesis, and 20 healthy subjects were studied, using visual and spectral coherent EEG analysis and investigation of three-dimensional localization of dipolar beta 1-activity sources (13-20 Hz EEG bands). In Korsakoff's syndrome, negative prognostic significance of a stable increase of EEG beta 1-activity coherence generated by a limited number of sources, preferably of frontal basal and stem localization, was found. In the context of clinical data, this EEG phenomenon may be related to inhibited state of corresponding cortical areas.

[Intercentral EEG relationships in regressive and chronic post-traumatic Korsakoff syndrome]. / Mezhtsentral'nye otnosheniia EEG pri regressiruiushchem i khronicheskom posttravmaticheskom Korsakovskom sindrome.

Dynamic EEG study of patients with posttraumatic Korsakoff's syndrome (KS) with the application of complex analysis methods revealed a complicated pathological structure of the intercentral relations of cortical electrical activity. The interhemispheric EEG coherence between symmetrical frontal cortical areas are sharply reduced, while the intrahemispheric coherence are increased in comparison with the normal values. The proposed technique of segregation of statistically homogeneous spectro-coherent characteristics made it possible to reveal the earlier intercentral EEG relations formed by stable and variable coherence spectra. The structure formed by the stable and variable coherence spectra in KS differs from that reflected in the mean coherence levels. During the KS regression, the EEG coherence between the right and left frontal areas increased to the normal level, and the variable spectra are revealed. In the chronic KS syndrome, the pathological intercentral relations persist, while the variable relations in the frontal areas are absent. A reduction of pathologically decreased intrahemispheric coherence selectively revealed in the right hemisphere during the KS regression and formation of variable relations in this hemisphere point to a leading role of the right hemisphere in development of compensatory processes in KS. The reciprocal relations between the intra- and interhemispheric coherence and coherence dynamics in the theta rhythm suggest that pathological activity in the basal diencephalic structures plays an important role in formation of the pathological EEG pattern in KS.

[The electroencephalographic correlates of a disorder in higher cortical functions in local lesions of the hypothalamic area]. / Elektroéntsefalograficheskie korreliaty narusheniia vysshikh korkovykh funktsii pri lokal'nykh porazheniiakh gipotalamicheskoi oblasti.

In order to reveal correlations between disturbances in higher cortical functions and characteristics of electrical activity 70 patients with pathological foci in the hypothalamic regions were examined using computer data processing. Destruction of the normal intercentral relations between EEG rhythms develops under the influence of the hypothalamic focus. The process builds up with the aggravation of cortical disorders (mnestic, emotional-affective, consciousness oppression with sleep inversion). General decrease of EEG coherence is observed with the highest destruction of correlations in the frontal cortical areas. The structure of high-frequency alpha-rhythm becomes deranged even in slight cortical disorders, its coherence decreases predominantly in the frontal cortical areas. With intensification of the pathological process in the focus, the stage of delta-rhythm coherence increase is observed and at the background of general destruction of correlations new, pathological intercentral relations develop. Using a BRAINLOC computer technique "sources" of the delta- and theta-activity have been localized in the medio-basal brain regions. The area of localization is specific for hypothalamic lesions. The "source" is mostly expressed in the slightest pathology of higher cortical functions. With aggravation of the process in the hypothalamic pathological focus and further derangement in the cortical functions expression of the "sources" reduces up to their complete disintegration in coma.

[Compression spectrum analysis of the EEG in severe cranio-cerebral trauma]. / Kompressionnyi spektral'nyi analiz EEG pri tiazheloi cherepno-mozgovoi travme.

Analysis of the quantitative values of compression spectrum analysis (CSA) of the EEG obtained in 53 examinations of 21 patients with severe craniocerebral trauma on the basis of multidimensional statistical and factor analysis made it possible to reveal signs which correlated best with the clinical data. Spatial and time characteristics of CSA, the variability of standardized capacities according to the ranges of physiological rhythms in particular, proved to be most informative as regards the prognosis.