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Biomedical subjects

E V Sharova

Publications and source records attributed to E V Sharova.

At least 19 recordsLinked to original sources
PubMed2004

Characteristics of brain bioelectrical activity in post-traumatic Korsakov's syndrome.

A total of 32 patients (21 with reversible and 11 with chronic Korsakov's syndrome of traumatic origin) and 20 healthy controls were studied. Visual and spectral coherence analysis was applied to EEG recordings and the three-dimensional localization of equivalent dipole sources of beta1 activity in the frequency range 13-20 Hz. Stable increases in the coherence of EEG beta1 activity generated by a limited number of sources (mostly frontobasal and brainstem locations) had negative prognostic significance in Korsakov's syndrome. Comparison with clinical data allow this EEG phenomenon to be linked to the inhibitory state of the corresponding cortical zones.

Adolescent↗
PubMed2003

[Component P300 of acoustic evoked potential in patients with local brain lesion].

The aim of the study was a comparative analysis of spatial-temporary organization of P300 acoustic evoked potential (AEP) in patients with local lesions of the brain stem, frontal and temporal structures in the situations of "passive" listening to sounds and their active recognition (a count). Specific changes of P300 parameters were distinguished in each group. The peak-temporary P300 parameters--latency increase, decrease of amplitude and tendency to the decrease of half-cycle--were similarly changed, irrespective of brain damage topography. A degree of the changes correlated with a level of functional acoustic evoked potential decompensation. In relation to pathologic process location, the topographical P300 AEP features were more specified, comparing to peak-temporary parameters. An existence of two systems for P300 generation at "active" counting and "passive" listening was suggested. In "passive" listening, a response is mostly determined by intact left frontal lobe and middle-stem structures but in "active" counting--by intact right frontal lobe or lobes and limbic system structures (hippocampus).

Adult↗
PubMed2003

[Particular aspects of bioelectric brain activity in post-traumatic Korsakoff syndrome].

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.

Adolescent↗
PubMed2001

[EEG peculiarities in posttraumatic Korsakov's syndrome].

The paper presents an attempt to define the structures of the cerebral functional pathologic system in the Korsakov's syndrome (KS) that develops after a severe craniocerebral trauma. 32 patients with reversible (21) and irreversible (11) KS variations were examined. Visual and coherent EEG-analysis was performed as well as determination of the three-dimensional location of the equivalent dipole sources of the separate pathologic components of the bioelectric activity. The data obtained were compared with the clinical ones. The role of both diencephalic and subcortical (including hippocampus) structures in KS development as well as the role of the right hemisphere were confirmed. Significance of the anterior (temporal-frontal-central) regions of the right hemisphere in KS regression was found. The degree of the injury of nonspecific frontal and brain stem structures and involvement of the left hemisphere into the pathological process together with the right one is essential for KS reversibility.

Adolescent↗
PubMed1988

[Effect of piracetam on the functional activity of the brain in patients with craniocerebral injuries].

Repetitive EEG spectral analysis in 32 patients after severe of mild head trauma revealed two types of responses to Piracetam evidencing the ambiguity of its effect on unspecific activating brain structures. Besides the brain cortex, the hypothalamo-thalamic system was found to participate in the response. With epileptoid signs present in the EEG, the drug could reduce the seizure threshold.

Brain↗
PubMed1985

[Recovery of consciousness after prolonged coma in patients with severe craniocerebral injuries].

The authors specify and describe 7 stages of regaining consciousness by patients who had been in coma from 11 to 180 days, including opening of the eyes; fixation of the eyes on an object; recognition of close relatives; understanding of directly addressed speech; patient's own speech; amnestic confusion; consciousness with all formal signs of being clear. The condition of the patients at these stages is compared with EEG findings suggestive of the functional disintegration of the brain as a system in comatose patients, the vegetative status and the restoration of connections between different departments of the brain corresponding to the recovery of long absent consciousness of patients. It is concluded that at the current stage of medical sciences the maximum duration of coma compatible with the subsequent full recovery of mental activity of the patient under 30 years does not exceed 11 days.

Adolescent↗
PubMedDate not supplied

Intercentral relationships of cortical bioelectrical activity of the human brain following operative interventions in brainstem structures.

The dynamics of the total bioelectrical activity and the parameters of its intercentral interaction was investigated in 52 neurosurgical patients with a focal lesion at the level of the brainstem with the aim of analysis of the compensatory neurodynamic reorganizations of the human brain in the early postoperative period. The study was based on the precise verification of the topography of the pathological focus within the limits of the brainstem; on the dynamic clinical-neurological assessment of different variants of the postoperative course; and on a study of the structure of cortical bioelectrical activity based on visual and spectral coherence analysis. The dependance is demonstrated of the compensatory neurodynamic reorganizations of the brain on the character and degree of the stem lesion (transitory, stable, irreversible).

Brain Stem↗
PubMedDate not supplied

[Visual evoked potentials and the P300 component in different courses of the posttraumatic vegetative state].

The late latency components of visual evoked potentials (VEP) and the component P300 AEP were analyzed to evaluate their informative value in the process of mental function restoration in patient after long-term traumatic coma. VEP components with latencies of 70 to 320 msec were studied in 24 patients. Topographical mapping of the power of the study VEP components and components P300 was made by the peak amplitude. Long-term VEP components and component P300 were examined by the method of three-dimensional localization of equivalent dipole sources. In 16 patients with positive tendencies in the condition there was a stable localization of the maximum VEP power in the parietal, sagittal, and occipital regions, component P300 showed its maximum amplitude in the central and parietal regions in the left hemisphere. Eight patients with negative tendencies in the status had the maximum VEP and component P300 in the frontal and temporal regions, predominantly in the right hemisphere. The paper shows it important to evaluate not only time-amplitude parameters and analyzes the tomographic features of its formation in dynamics.

Acoustic Stimulation↗
PubMedDate not supplied

[The effects of combined electrolytic brain stem-orbitofrontal and brain stem-hippocampal damages to the rat brain].

Morphofunctional studies of animals with associated electrolytic orbitofrontal and hippocampal brainstem lesions as compared to variants of isolated brainstem coagulation showed participation and specific role of orbitofrontal cortex and hippocampus in adaptive-compensatory brain reactions of rats with brainstem lesions. Associated brainstem-orbitofrontal damages result in aggravation of the animals' condition and highly probable lethality within the first two weeks after surgery due to blood circulation dysregulation of hemorrhagic type and probably due to secondary hypothalamus dysfunction. Associated brainstem-hippocampal coagulation intensifies primarily brainstem neurologic symptoms and prolongs time of their reverse development, i.e. supports the brainstem centre of stable pathological activity.

Animals↗
PubMedDate not supplied

[Characteristics of the spatio-temporal organization of the P300 component of AEP during the "active" and "passive" stimulus perception in healthy subjects].

The concern of the work was in detection and analysis of P300 component of the acoustic evoked potential in healthy subjects in different experimental situations. During counting the rare sounds, P300 was most pronounced in the frontocentral and parietooccipital areas mainly of the left-hemisphere. The response shape was correlated with characteristics of the basic rhythm of the background EEG. Responses of simple and complex shapes were distinguished. The simplest responses were recorded in subjects with hypersynchronous alpha-rhythm. Analysis of three-dimensional dipole source localization showed that structures of the brainstem, limbic system, and frontal lobes participate in generation of the wave. In all the subjects, the decisive role in response generation was played by the brainstem structures. In persons with hypersynchronous alpha-rhythm, the contribution of the frontal lobes was less pronounced. During "passive" listening of sounds, P300 parameters significantly differed from those observed during counting only in 46% of cases (in persons having no hypersynchronous alpha-rhythm). A simplification of the response shape during "passive" listening was observed in these cases, the area of the maximal response expression was shifted to symmetrical areas of the right-hemisphere, the number of dipole sources reduced due to a decrease in the contribution of the frontal and limbic structures into the response generation.

Adolescent↗
PubMedDate not supplied

[Rat brain reactions to acute brain stem lesion on dynamics of parameters of cerebral electric activity].

Despite an old history of a question, adaptive brain reactions that develop after an acute brainstem lesion have not been adequately investigated. With the aim to study the central mechanisms of compensation/decompensation and to specify the character of involvement of orbitofrontal cortex and hippocampus into these processes the spatiotemporal organization of brain electric activity was analyzed in 8 rats before and after electrolytic brainstem lesion at the level of the lateral vestibular nucleus Deiters (VND). The electric activity was recorded from symmetric frontal and somatosensory cortical areas, hippocampal areas CA1, and intact VND. Spectralcoherent analysis showed that adaptive reactions are most clearly manifested by changes in the spatiotemporal organization of the theata activity: 1) early brainstemhippocampal synchronization of the electric activity in the frequency range of 6-7 Hz with subsequent involvement of anterior cortical regions is characteristic of survived animals; 2) independent hippocampal-cortical hemispheric system of excitation in the frequency of 4-5 Hz precedes the fatal outcome. On the day before the fatal outcome the interhemispheric coherence in the orbitofrontal cortex dropped, which suggests the involvement of these brain regions into the processes of visceral regulation.

Animals↗
PubMedDate not supplied

[The reflection of different levels of the regulation of human brain activity in spectrally coherent EEG parameters].

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.

Brain↗
PubMedDate not supplied

[Intracerebral EEG functioning as a reflexion of the systemic brain organization in norm and pathology].

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.

Brain Injuries↗