[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 and fMRI reactions of a healthy brain at active and passive movements by a leading hand].

Bioelectrical (EEG) and hemodynamic (fMRI) responses of cerebral reactions to active and passive movements by the right hand were analyzed in 17 right-handed healthy persons. Individual and averaged fMRI and EEG data was analyzed. The main cortex fMRI responses (sensorimotor cortex of the contralateral, left hemisphere) were topographically similar during both active and passive movements. This fact allows us to recommend the usage of the passive movement paradigm for the mapping of the motor areas in patients with movement disorders. Including in reactive process of cerebellum and subcortical structures at passive movements was more variability than active ones. FMRI-reactions at passive movements were characterized more individual variability than during active ones at the expense of diversity of cerebellum and subcortical structures answers. The EEG analysis revealed that at both passive and active movements there is a coherence increase in the high-frequency alpha-ban in left central-frontal area of the left, activated hemisphere. The power-frequency changes of the EEG parameters during active and passive movements were primarily shown in a frequency increase and the desynchronization of the beta-band. Consistency with the topography of the fMRI response was not found.

[Structural and functional peculiarity of brain activity to performance and imaginary motor tasks in healthy persons (EEG and fMRI study)].

Bioelectrical (EEG) and hemodynamic (fMRI-response) cerebral reactions to performance and imaginary motor tasks by right or left hand were analyzed in 15 right-handed healthy persons (21-39 years old). During actual movement the main fMRI-response was registered in the area of central gyrus of the hemisphere contralateral to the working hand. Areas of activation were also revealed in the supplemental motor area and the ipsilateral hemisphere of the cerebellum. EEG data showed coherence increase in high frequency alpha- and beta-bands in the activated hemisphere. In imaginary motor tasks the intensity and topography of fMRI-response became the more variable; response was decreased in the motor area and in cerebellum, they increased in the subcortical structures and in the parietal association zones. EEG changes were very variable in this situation also; it was observe an increase of EEG coherence in the right hemisphere for higher frequency of alpha and beta spectral bands. Changes of power spectrum parameters were similar to performance and imaginary motor tasks. Spectrum power and middle frequency of beta band were increased. Topographically these changes did not correspond to activated hemisphere and it was more in the left hemisphere. These changes were reflected nonspecific component of reaction.

[fMRI study of the dominant hemisphere for language in patients with brain tumor].

THE AIM OF THE STUDY: Paper describes a study of language lateralization of patients with brain tumors, measured by preoperative functional magnetic resonance imaging (fMRI) and comparison results with tumor histology and profile of functional asymmetry. METHODS: During the study 21 patient underwent fMRI scan. 15 patients had a tumor in the left and 6 in the right hemisphere. Tumors were localized mainly in the frontal, temporal and fronto-temporal regions. Histological diagnosis in 8 cases was malignant Grade IV, in 13 cases--Grade I-III. fMRI study was perfomed on scanner "Signa Exite" with a field strength of 1.5 As speech test reciting the months of the year in reverse order was used. fMRI scan results were compared with the profile of functional asymmetry, which was received with the results of questionnaire Annette and dichotic listening test. RESULTS: Broca's area was found in 7 cases in the left hemisphere, 6 had a tumor Grade I-III. And one patient with glioblastoma had a tumor of the right hemisphere. Broca's area in the right hemisphere was found in 3 patients (2 patients with left sided tumor, and one with right-sided tumor). One patient with left-sided tumor had mild motor aphasia. Bilateral activation in both hemispheres of the brain was observed in 6 patients. All of them had tumor Grade II-III of the left hemisphere. Signs of left-handedness were revealed only in half of these patients. Broca's area was not found in 4 cases. All of them had large malignant tumors Grade IV. One patient couldn't handle program of the research. CONCLUSIONS: Results of fMRI scans, questionnaire Annette and dichotic listening test frequently were not the same, which is significant. Bilateral activation in speech-loads may be a reflection of brain plasticity in cases of long-growing tumors. Thus it's important to consider the full range of clinical data in studying the problem of the dominant hemisphere for language.

[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.

[Dynamics of P300 component of acoustic evoked potential in postraumatic unconsciousness].

In order to reveal features of the brain reactions to external stimuli in the course of consciousness recovery after a severe craniocerebral injury, component P300 of acoustic evoked potential was analyzed in 9 patients with chronic and 32 patients with reversible unconsciousness. In patients with chronic unconsciousness, P300 parameters displayed a linear correlation with the current functional state. However, this component remained significantly different from its normal shape and varied only in a narrow range. In patients with reversible unconsciousness, time course of changes in amplitude and latency between recovery stages was of linear character with a tendency to normalization. The findings suggest that, in reversible unconsciousness states, processing of sensory information at different recovery stages may be performed with various functional systems that determine varying quality of processing, whereas changes in chronic unconsciousness are caused by a decrease in the number of active elements within the same functional system.

[The electrophysiological correlates of the involvement in a pathological process of the thalamo-hypothalamic structures of the human brain]. / Elektrofiziologicheskie korreliaty vovlecheniia v patologicheskii protsess talamo-gipotalamicheskikh struktur mozga cheloveka.

Comparative EEG studies (with the normative data control) were carried out in patients with different anatomic-topographical variants of craniopharyngioma, effecting the hypothalamus (12 patients) and involving thalamo-subcortical structures in the pathological process (17 patients). Characteristics of EEG reorganization were found to be determined in the first instance by the stage of development of the focal process. Analysis of the regional characteristics and intercentral relations of the brain biopotentials revealed besides the common features, the differences in the effects of certain diencephalic structures on the spatial-temporal EEG organization. Hypothalamic areas exert mainly global influence on the EEG pattern formation. Thalamic structures influence genesis of the rhythmic activity forms and their intercentral relations more differentially and make more important contribution to the formation of the balanced (in norm) pattern of the brain electrical processes spatial-temporal organization.

[Characteristics of the interhemispheric EEG relationships in assessing the functional state of the human brain]. / Kharakteristika mezhpolusharnykh vzaimootnoshenii EEG v otsenke funktsional'nogo sostoianiia mozga cheloveka.

In healthy subjects (11 right-handed men) reorganization was studied of intra- and interhemispheric correlation of the electrical brain activity at transition from the state of alertness to drowsiness. At the lowering of alertness level, the coherence of hemispheres symmetrical points changed not abruptly, with a tendency towards an increase at differently directed character of changes of combinations of separate physiological rhythms ranges. Comparison of the EEG coherence changes within the right and left hemispheres revealed a greater reactivity of the left (dominant) hemisphere. The reduction of the predominance (observed in the dominant hemisphere in alertness) of the degree of EEG conjunction, at transition to drowsiness, leads to smoothing of interhemispheric asymmetry in the organization of electrical brain processes.

[Evoked potentials to joint presentation of photic and acoustic stimuli in the human EEG]. / Vyzvannye potentsialy na sovmestnoe pred"iavlenie svetovykh i zvukovykh stimulov na EEG cheloveka.

The results are outlined of a comparative estimation of averaged EP recorded in response to simultaneous and separate presentation of photic and acoustic stimuli on EEG of fifteen healthy subjects and twelve patients with focal lesions of the diencephalic structures. Investigation of the EP components and integral-temporal parameters has revealed that in healthy subjects EP to a combined heteromodal stimulation considerably exceeded by amplitude the one recorded in response to a separate presentation of stimuli. In case of lesion of the diencephalic formations, the converging effect of polysensory stimulation for the main waves of the response was less pronounced than in healthy subjects. At the same time, in pathological cases the summation effect of the afteraction potential (recorded after the main EP components as a slow negative oscillation) was manifested most distinctly, especially in the central zone of the cortex.

[Dependence of the organization of human brain electrical activity on hemispheric dominance]. / Zavisimost' organizatsii élektricheskoi aktivnosti mozga cheloveka ot dominantnosti polushariia.

In healthy subjects, in a state of relative rest, with different individual profiles of asymmetry (20 right-handed and 10 left-handed subjects), a greater conjunction of electrical brain processes (estimated by mean EEG coherence levels) has been found in the dominant hemisphere as compared to the subdominant one, more distinctly expressed in the right-handed subjects. The maximum degree of interhemispheric asymmetry of the EEG coherence is observed in the posterior associative cortical areas. Specific interhemispheric theta-range differences are revealed as compared with other EEG frequency bands. Greater values are obtained of the correlation of the EEG symmetrical hemispheres points in the whole frequency band and in alpha- and beta-ranges in the right-handed subjects than in the left-handed ones.

[A search for the sources of pathological alpha activity in the human EEG in limbic structure lesions]. / Poisk istochnikov patologicheskoi al'fa-aktivnosti EEG cheloveka pri porazhenii limbicheskikh struktur.

Dependence of manifestations of EEG pathological activity on the electrode montage was studied in cases of brain lesions involving limbic structures by means of the topographic mapping and 3-d dipole source localization. The original program DIPVIS on the basis of BRAINLOC software allowed us to reveal the stable sources of lateralized pathologic alpha activity and demonstrate the discrepancy between its localization and the localization of the normal human alpha rhythm. The sources of pathological activity in question were predominantly localized in the mediobasal structures of the affected hemisphere in contrast to the occipital region of a healthy human. It was established that the topography of the cortical pathological activity may be determined by peculiarities of localization and, especially, orientation of its dipole generators. Afferent stimulation produced an enhancement of the pathological alpha-activity and increase in dipole source concentration in the mediobasal portion of the temporal lobe. The findings suggest that the discovered from of the alpha-rhythm reflects the reaction of activation of the hippocampal structures involved in the pathological process.

[Adaptive-compensatory restructurings of the intrahemispheric interaction of electrical processes in the human brain in brain stem lesions]. / Adaptivno-kompensatornye perestroiki vnutripolusharnogo vzaimodeistviia élektricheskikh protsessov mozga cheloveka pri porazhenii stvolovykh struktur.

In 50 patients with focal lesions of the brainstem was analysed the postsurgery dynamics of the interhemispheric interaction (by the characteristics of EEG coherence). Was shown a specific participation of the left and the right hemispheres in a realization of postoperative compensatory brain reactions. In survived patients in early terms after surgery the phase was revealed in which coherence in the left hemisphere exceeded that in the right one and the difference being significant for the frontal areas. This phenomenon reflected higher reactivity of the dominant hemisphere in a realization of the adaptive reactions of the CNS. Right hemispheric EEG coherence in general had lower values and was more inert. It dominated under the conditions when only vegetative regulation remained before the lethal exit.

[Dynamics of the spectral-coherent characteristics of the human EEG in healthy subjects and brain pathology]. / Dinamika spektral'no-kogerentnykh kharakteristik EEG cheloveka v norme i pri patologii mozga.

EEGs of 15 healthy subjects and 30 patients in early period after surgical ablation of tumours with basal localization, were investigated by means of monitor "Neuro-1" which allows to obtain in continuous regime characteristics of EEG dynamics according to power spectra and reveal the characteristics of intercentral relations of electrical brain processes by coherence and phase shifts. In healthy subjects in the period of transition from wakefulness to drowsiness highly coherent beta-rhythm (16-18 Hz) was revealed, preceeding typical picture of drowsiness and sleep. Study of the patients shows that certain characteristics of coherence and phasic shifts have an important prognostic value. Conclusion is made that for estimation of the functional state of healthy subjects during transition from wakefulness to drowsiness and of patients in early postoperative period the data on spectra of coherence are most informative.

[The reflection of the adaptive restructurings of the human brain in disordered cerebral functions in the parameters of interhemispheric asymmetry in EEG coherence]. / Otrazhenie adaptivnykh perestroek mozga cheloveka pri narushenii tserebral'nykh funktsii v parametakh mezhpolusharnoi asimmetrii kogerentnosti EEG.

In this work was studied a hemispheric specificity of the human brain in a realization of adaptive-compensatory reactions of the CNS. The interhemispheric correlation of EEG coherence functions of the left and the right hemispheres was computed in patients with brain focal lesions in early postsurgery period after an extraction of the medially-located tumor or in far-off time after a hard brain injury (i.e. at different stages of cerebral compensation). The observed peculiarities of changes of the interhemispheric biopotential relations revealed the dynamic character of preferable switching on the right or the left hemisphere in a formation of adaptive-compensatory brain reactions. The specificity of this switching depended on the stage of the pathologic process and reflected the degree of consciousness disturbance.

[The reflection of different levels of the regulation of human brain activity in spectrally coherent EEG parameters]. / Otrazhenie raznykh urovnei reguliatsii mozgovoi deiatel'nosti cheloveka v spektral'no-kogerentnykh parametrakh EEG.

On the basis of clinico-anatomo-electroencephalographic studies it was shown, that in early terms of cerebral trauma, at gross disturbances of the cortical functions and safety in some cases of only vital regulation, the parameters of the EEG stability or variability are of distinct information value for estimation of the functional state of patients. It was established, that changes of stability of the frequency, power, and coherent EEG characteristics correlate with different parameters of changes of the structural-functional brain organization. At this stage the greatest connection with the disease outcome reveals the EEG coherence parameters of the cortical symmetrical points reflecting the state of predominantly median formations and general brain reactions to traumatic action. In the process of restoration of disturbed neuromental functions priority prognostic significance is acquired by parameters of intrahemispheric coherence as well as by frequency-regional properties of interhemispheric asymmetry of coherence of the brain electrical processes, characterizing functional features of the lesion focus.

[Spectral analysis of the EEG and intracortical connections in the presence of a pathologic focus at different levels of the human brain]. / Spektral'nyi analiz EEG i intrakortikal'nye sviazi pri nalichii patologicheskogo ochaga na raznykh urovniakh golovnogo mozga cheloveka.

EEG spectral analysis in 68 patients with focal brain lesions has shown that EEG power spectra are characterized by greatest changes in the focal zone, as manifested in the augmenting of the slow component and diminution of the alpha-component. By means of phasic analysis it has been established that the slow component is generated in the focal zone. Analysis of the complex function of EEG coherence detected different variants of changes in the spatial-temporal organization of cortical electrical activity, determined by localization of the focus and the extent of its impact on the brain. The revealed discordance of EEG connections, diminution of coherence in some parts of the hemispheres with simultaneous enhancement in the others, manifested differently in different physiological rhythms ranges, reflects an impairment in the structure of intracortical connections of electrical processes, which is typical of the normal brain.

[Symmetry and stability of the EEG spectra of healthy subjects]. / Simmetrichnost' i stabilnost' spektrov EEG zdorovogo cheloveka

Stability and symmetry of power spectra and the EEG coherence function have been investigated in 40 healthy subjects with different characteristics of cerebral electrical activity. It has been shown that the power spectra in all healthy subjects are characterized by a high degree of symmetry and stability. The average levels of coherence of the symmetric points of the right and left hemisphere proved to be a reliable EEG characteristics of a healthy subject. In contradistinction, the pattern of the coherence spectrum displays considerable variability and non-stability. Subjects with a desynchronized EEG differ from those with alpha-rhythm predominance by the highest coherence and similarity of the spectra along with their low stability in the anterior parts of the hemisphere which testifies to a high dynamic integration of the frontal systems.

[Intracerebral EEG functioning as a reflexion of the systemic brain organization in norm and pathology]. / Mezhtsentral'nye otnosheniia EEG kak otrazhenie sistemnoi organizatsii mozga cheloveka v norme i patologii.

The authors summarized the EEG findings and defined the nature of intercentral EEG relationships in different functional states of healthy subjects and patients with organic cerebral pathology based on coherence analysis. The EEG features typical of healthy subjects were identified: an anterior-posterior gradient of the mean coherence and the character of cortical-subcortical relationships in the anterior cerebral structures. Right- and lefthanded subjects showed the frequency and regional differences in EEG coherence, which reflected, mainly, specific intracortical relationships. Development and regression of pathologic signs in right- and lefthanded patients with organic brain lesions are thought to be determined by these differences. As distinct from cortical pathology, lesions of regulatory structures (diencephalic, brainstem, and limbic) were shown to produce more diffuse changes in intercentral relationships with a tendency to reciprocity. Intercentral relations, including their interhemispheric differences, varied with changes in the functional state of healthy subjects (increase and decrease in the level of functioning). A certain time course of changes in intercentral relationships was also revealed in patients with organic brain lesions during recovery of their consciousness and mental activity. Changes in the dominance of activity of individual regulatory structures are considered to be one of the most important factors that determine the dynamic character of EEG coherence.

[EEg changes after removal of craniopharyngiomas in children]. / Izmeneniia EEG posle udaleniia kraniofaringiom u detei.

Electroencephalograms (EEG) were studied after removal of craniopharyngioma in 75 children. Correlation of the character of ECG changes with the severity of the clinical condition was revealed. Maximally manifested pathological EEG activity of the central areas of the cortex and a phase character of the EEG changes with different duration of the phases determined by the patient's condition were common to all patients, irrespective of the severity of their condition which was determined by the degree of the pathological changes in the thalamo-hypothalamic structures. Prognostic signs of the EEG changes were identified, which characterized a favorable or a complicated course of the postoperative process.