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We have analyzed EEG alterations during a passive hand movement test in ten patients with varying degrees of hemiparesis caused by brain injury and compared them with normal data (17 healthy volunteers). The fMRI responses of the patients were normal. It was found that additional brain structures (that seem to be untypical of healthy people) are included in the reactive process in patients with brain injury. Additionally, we observed a widening of affected frequency bands. We observed the highest correlation with the degree of hemiparesis for the topographical parameters of changes in EEG coherence during the passive hand movement test with specific response features of the brain hemispheres contra- and ipsilateral to the movement. It is discussed whether there is any involvement of the tactile component in the passive motor EEG response. The data are considered in the context of the earlier hypothesis [1, 2] on the participation of the extrapyramidal system in the compensation of a post-traumatic motor defect.

The results of the EEG study of patients with tumor lesion of diencephalic (29 subjects) and limbic (25 subjects) structures with the focus on the analysis of structural and functional organization of α activity have been summarized. It has been found that diencephalic structure dysfunction is accompanied by disorder of α-rhythm spatial organization in the form of generalization or translocation of its focus to the frontal regions of the cerebral cortex. Distinctive features of “diencephalic” type alteration of α rhythm are determined by predominant integration of the thalamic or hypothalamic structures into the pathological process. Involvement of the limbic structures, especially at early stages of the disease, induces increase in α-rhythm intensity in the temporal region of the affected hemisphere. The nature of the response of the EEG pattern to the functional stress allows identifying it as a “hippocampal α rhythm”. Implementation of the automatic methods of analyzing plays an important role in the identification of these specified pathologic forms of the α rhythm that are often invisible during visual assessment. Detected atypical forms of α rhythm facilitates the interpretation of hemispheric asymmetry of the EEG in patients with cerebral pathology.

The hemodynamic (magnetic resonance imaging, fMRI, 3T) brain responses were studied in 15 left-handed healthy subjects performing active and passive movements of the dominant and non-dominant hands. Group and individual fMRI responses to the motor load were analyzed. It was found that, during the active movements of dominant and non-dominant hands, the main activation cluster appeared in the preand postcentral gyrus of the contralateral hemisphere and which topographically similar during active and passive movements. The activation cluster of greater volume was identified in these areas; the response was more diffused during the non-dominant hand movements in comparison with the dominant hand. During passive movements, the cortical activation clusters of a smaller volume in comparison with the active movements were found, which was expressed most clearly during the performance of non-dominant hand movements and could reflect the weakening of the control from the cortical structures in these conditions.

Functional magnetic resonance imaging (fMRI) was used to study the variation of functional changes that arise in the brain in response to similar tests in healthy subjects. The approach was assumed to demonstrate diverse individual strategies of achieving the same external (behavioral) response via different brain mechanisms and to identify the factors responsible for the diversity. Hemodynamic (fMRI) responses to activation of attention while opening the eyes or performing motor (consecutively moving the fingers of the right and left hands) and speech (mentally repeating the months of the year or the days of the week in the backward order) tests were determined in 21 healthy subjects aged 21–30 years, including 14 males and 7 females. A variation in fMRI responses was observed, i.e., three or four types of reactive hemodynamic changes were seen in the same test in the group, the prevalence of each type varying from 40 to 10% in one test. The responses showed distinct gender differences, and their specifics depended on the nature of the functional test. In motor and speech tests performed with the eyes closed, the fMRI responses in the females were more specific and local than in the males. In motor tests, the fMRI responses of the males compared with the females were characterized by a greater involvement of the frontal regions, which are responsible for regulatory functions. In the activation test (eye opening), the fMRI responses were more diffuse in the females and more local in the males.

A comprehensive study with the assessment of reactive responses to motor tasks was performed in nine patients with a tumor localized in the frontal divisions of the brain using two methodological approaches: functional magnetic resonance imaging (fMRI) and EEG. The data obtained were compared to the results of a similar study on 12 healthy subjects. It was established that cerebral pathology was associated with disorders of functional specialization and an increase in the diffuse component of reactivity. The fMRI responses were characterized by greater intactness compared to the EEG parameters of reactive changes. These features are especially marked when an afferent stimulus is sent to the damaged hemisphere. The characteristics of the involvement of individual EEG bands in the formation of motor responses and changes in the fMRI response topography are determined by the degree of cerebral dysfunction reflected by the pattern of baseline EEG reorganization and the severity of the motor defect. The predominant increase in the coherence of slow rhythms in the damaged hemisphere irrespective of the target of the afferent stimulus in patients with severe cerebral dysfunction reflects the dominant formation of a pathological focus and is indicative of a greater, compared to healthy subjects, involvement of deep brain structures in the reactive process, which is confirmed by the fMRI data.

The functional magnetic resonance imaging (fMRI) and EEG responses to identical functional (visual and motor) loads have been compared in ten healthy subjects with the use of individual structural MRIs of the brain. It has been established that an increase in the coherence of the EEG α waves corresponds mostly to the zone of the fMRI response (as a +BOLD reaction). Reactive rearrangements, according to the data of fMRI and, particularly, EEG studies, are characterized by pronounced interindividual variation, which increases along with the functional test complexity. The fMRI responses have shown a greater locality and closer dependence on the modality of presented stimuli than EEG rearrangements, which underline the systemic character of brain response to functional loads. The −BOLD response accompanying the local +BOLD effect is more generalized, without distinct topographic referencing to the functional load modality; it conforms most of all to the decrease in the EEG’s coherence.

In order to determine more accurately the EEG markers of different types of attention (AT) of a healthy adult, 14 young healthy subjects (aged 18–30 years) were subjected to spectral coherent analysis of the electrical activity of the brain in the baseline state and during activation of different forms of AT (the orienting response to the sound tone and opening of the eyes, involuntary and voluntary visual AT). In the last two cases, specially developed computer-aided techniques were used. The quantitative differences in the states were assessed on the basis of nonparametric (the Mann-Whitney test) and parametric (Student’s t test) statistics. In three subjects, EEG and fMRI comparisons of the brain response to opening of the eyes were made. It was shown that the activation of different forms of AT in healthy subjects is accompanied by considerable diffuse nonspecific changes in the EEG spectral coherent characteristics (a decrease in the average spectral frequency and power, as well as in coherence) in combination with more local, more often oppositely directed shifts in the region of the cortical representation of the working analyzer. Complex systemic rearrangements of the brain activity involving all components of the activating system, as well as the specifics of different forms of AT connected with the rearrangement of activity between its divisions, are reflected in the diffuse changes of intercentral interaction. For example, marked reactivity of the symmetrical frontopolar (Fp1-Fp2) and the anterotemporal (F7-F8) cortical areas with unidirectional maximum shifts during voluntary AT is likely to reflect the responses of the frontothalamic component of the activating system. The reciprocity of the behavior of interhemispheric frontopolar and temporal relationships seems to be determined by the activity of its different components: frontothalamic and hippocampal. The local component of the EEG response to opening of the eyes in the form of increased α coherence in the occipital areas is coupled with increased oxygenation of blood in the cortical representation of the visual analyzer (the +BOLD effect of the fMRI response).