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Biomedical subjects

O M Grindel'

Publications and source records attributed to O M Grindel'.

At least 37 records · Page 2Linked to original sources
PubMedDate not supplied

[The low-frequency EEG component in the healthy subject and its changes as affected by acutely developing foci at the level of the diencephalon and brain stem structures].

The data are given of the analysis of the low-frequency EEG component (LF EEG--0.2--2.0 Hz) of 34 healthy subjects and 36 patients examined in dynamics in the acute period after operations: ablation of a tumour localized at the level of the diencephalon and the level of the brainstem. The LF EEGs were analyzed by a special program: auto- and crosscorrelation functions and power spectra were estimated. In the norm LF EEGs were characterized by mosaics, various frequencies and periodicity in various cortical areas, they appeared with interhemispheric asymmetry, depended on the EEG type--dominance or lack of the alpha-rhythm. In patients in the post-operative period the LF EEGs were changed; in favourable terminations, at first the period of oscillations and the coefficient of correlation increased, then they tended to normalization. In unfavourable terminations, with gross pathological foci in these areas, the LF EEGs acquired a synchronized character, with a higher frequency than in the norm.

Acute Disease↗
PubMedDate not supplied

[EEg changes after removal of craniopharyngiomas in children].

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.

Action Potentials↗
PubMedDate not supplied

[Dynamics of the spectral-coherent characteristics of the human EEG in healthy subjects and brain pathology].

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.

Beta Rhythm↗
PubMedDate not supplied

[Intercentral correlations in the cerebral cortex according to the EEG coherence index after restoration of consciousness and speech following prolonged coma].

Power spectra and coherence function of EEG of various cortical areas of both hemispheres were analyzed in 9 patients with extremely protracted loss of consciousness. Five patients were in the state of posttraumatic apallic syndrome lasting for more than 4 years in one patient, and 4-9 months with successive lethal outcome in 4 patients. One patient for more than 2 years was in a state of areactivity to external signals. In 3 patients the process of recovery of consciousness and speech began in 1-2 months. At the apallic syndrome, only low-frequency EEG components were present in spectrograms, and the values of coherence function were sharply decreased. With recovering consciousness and speech, a gradual appearance of alpha-activity was observed as well as an increase of coherence values at the frequency of the alpha-rhythm. The recovery of intercentral EEG relations in the motor-verbal cortical area was shown to play a special role in further normalization of connections in the cerebral cortex.

Brain Injuries↗
PubMedDate not supplied

[Spectral analysis of the human EEG in acutely developing foci of irritation at the diencephalic and brain stem levels].

The dynamic study of EEG spectra and coherence in 52 patients in early period after tumor ablation at the diencephalic (27 patients) and brainstem (25 patients) levels with favourable (24 patients) and lethal (28 patients) outcomes revealed a dependence of their changes on the reversibility or irreversibility of pathological irritation of these brain levels. At regressively developing foci and retained compensatory mechanisms characteristic changes of EEG relations were seen in the central cortical areas, i. e. in cortical projection zone of the nonspecific thalamic pathways. The changes observed consisted of EEG synchronization in the band of 7 cps and sharp coherence increase while changes of EEG correlations in other cortical areas were unsimilar. Gradual EEG normalization with alpha-rhythm restoration passed through the stage of sigma-rhythm and slow sleeplike waves which indicated the safety of brainstem-subcortical hypnogenic systems. In patients with destructive foci at the diencephalic and brainstem levels, i. e. under conditions of brain functioning similar to "cerveau isolé" and "encephale isolé",--a general coherence decrease and EEG synchronization in the band of 5 cps, or generalized slow, monomorphic oscillations were observed.

Brain Neoplasms↗
PubMedDate not supplied

[Spectral analysis of the EEG and intracortical connections in the presence of a pathologic focus at different levels of the human brain].

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.

Brain Neoplasms↗
PubMedDate not supplied

[Optimal level of EEG coherence and its importance in evaluating the functional state of the human brain].

The study of EEG by means of computer analysis 46 healthy subjects and more than 100 patients with different disturbances of consciousness showed that one of the necessary conditions for performance of reactions to external stimuli and higher nervous activity consists in the maintainance of optimal level of coherence of brain electric processes, corresponding to the optimal cortical tone. Different depths of disturbances revealed different coherence deviations from the optimal level: its overall decrease in case of deep disturbances (coma), a sharp (pessimal) rise in the low frequency rang in sopor and within a wide frequency range in drowsiness in norm. The recovery of consciousness in the post-coma period and at early stages of coma is accompanied by a discordance between the levels of EEG coherence -- a decline in some cortical parts and a sharp rise -- in other ones.

Alpha Rhythm↗
PubMedDate not supplied

[Analysis of human EEG spectra in a state of relative and "operative rest" according to A. A. Ukhtomskii].

The analysis of EEG in 40 healthy subjects showed that power spectra, coherence and phase spectra strongly vary in different subjects and that their spatial distribution among cortical areas bears individual properties. General characteristics of the spectra and mean levels of EEG coherence are stable, but details of power spectra, coherence and phases in healthy subjects are very unstable even within short time intervals. In the process of developing in the subject of a stable, ordered by experimenter state of a strained expectation of the signal to immediate activity--of "operative rest", according to A. A. Ukhtomsky--a uniform for all subjects structure of connections is shaped in frontal-central cerebral parts, which is manifested in a specific pattern of coherence spectrum.

Alpha Rhythm↗
PubMedDate not supplied

[The "midbrain waves" (MBW) in the human electroencephalogram].

The dynamic EEG study was performed in 19 patients with mesencephalic damages (verified by the contrast methods and during the surgery). A new EEG phenomenon, mesencephalic waves (MW), was observed in the early postsurgery period during the development of acute excitation focus. MW were recorded predominantly in the frontal and temporal neocortical areas. They appeared as a potential complex consisting of a negative monophasic wave with a superimposed one- or two-phasic spike followed by a 2-3 second theta-delta-burst. MW were recorded in 11 patients of 19 with mesencephalic damages and were not observed in the EEG of the control patients.

Brain Neoplasms↗
PubMedDate not supplied

[The electroencephalographic correlates of a disorder in higher cortical functions in local lesions of the hypothalamic area].

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.

Adenoma↗